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• UV-microbursts were measured by a highly sensitive photometer in auroral zone. • UV-microbursts are observed as series of pulses with complex time structure. • The relativistic electron microbursts origin of UV emission is considered. In this paper we present data on the UV-microburst (300–400 nm flashes with a duration less than 1 s) measurements in the auroral zone. Measurements were performed during the period 09.2021–04.2022 by the highly sensitive imaging photometer installed at the Verkhnetulomsky observatory of the Polar Geophysical Institute. It is shown that microbursts are grouped in a series with a duration from 10 s to 10 min. They were observed in relatively quiet geomagnetic conditions (K P < 3) at the southern boundary of the auroral oval in the evening magnetic local time (MLT) sector. UV-microbursts are observed in different observational conditions (clouds, transparent clouds and clear sky) and spatially represent various patterns: uniform diffuse illumination, local spots. Joint analyses of the optical measurements and satellite data on charged particle fluxes demonstrates that an auroral oval, characterized by a plasma, is placed to the north of the observatory. At the same time increased flux of electrons with energy more than 100 keV is observed at the same L-shell and MLT sector. The possible origin of the UV-microbursts is a precipitation of energetic electrons from a poleward boundary of the outer radiation belt in a form of relativistic electron microbursts is discussed. [ABSTRACT FROM AUTHOR]

The centrosome of the amoebozoan model Dictyostelium discoideum provides the best-established model for an acentriolar centrosome outside the Opisthokonta. Dictyostelium exhibits an unusual centrosome cycle, in which duplication is initiated only at the G2/M transition and occurs entirely during the M phase. Little is known about the role of conserved centrosomal kinases in this process. Therefore, we have generated knock-in strains for Aurora (AurK), CDK1, cyclin B, Nek2, and Plk, replacing the endogenous genes with constructs expressing the respective green fluorescent Neon fusion proteins, driven by the endogenous promoters, and studied their behavior in living cells. Our results show that CDK1 and cyclin B arrive at the centrosome first, already during G2, followed by Plk, Nek2, and AurK. Furthermore, CDK1/cyclin B and AurK were dynamically localized at kinetochores, and AurK in addition at nucleoli. The putative roles of all four kinases in centrosome duplication, mitosis, cytokinesis, and nucleolar dynamics are discussed. [ABSTRACT FROM AUTHOR]

This article discusses a study that validates the MAGNetosphere-Ionosphere-Thermosphere (MAGNIT) model against AMPERE measurements of field-aligned currents (FACs) during the "Galaxy 15" space weather event. The study compares the performance of three ionosphere electrodynamic models and finds that MAGNIT exhibits slightly improved predictions compared to other models. The article provides valuable information on auroral precipitation sources and their impact on FACs, which can be used to enhance the model. The study also analyzes various metrics and provides recommendations for optimizing the model's performance. [Extracted from the article]

Omega bands are mesoscale auroral structures emerging as eastward moving quasi‐periodic poleward protrusions well within the closed field line region of the auroral oval. Neither specific conditions of their appearance nor their causes are well understood. We perform a superposed epoch analysis of OMNI and SuperMAG measurements taken during 28 omega band events recorded by auroral all‐sky imager observations from 2006 to 2013 to identify their solar wind drivers. We find local enhancements in the solar wind flow speed, magnetic field, pressure, and proton density at the time of the omega band observation. In the magnetosphere‐ionosphere, we see enhancements in the ring current, partial ring current, and auroral electrojets. These features are consistent with geomagnetic activity caused by stream interaction regions (SIRs). 19 of our events overlap with SIRs from published event catalogs. Our findings suggest that omega bands are driven by compression regions commonly associated with SIR events. Plain Language Summary: Omega bands are eastward moving wave‐like structures in the aurora that typically appear at the equatorward border of the auroral oval during periods of enhanced activity in Earth's magnetosphere. However, the specific drivers of these structures are not well understood. In this work, we perform a statistical analysis of spacecraft observations taken from multiple omega band events to identify potential drivers of these structures. We find that the solar wind exhibits increased speed, pressure, and particle density when omega bands appear overhead. These features are consistent with localized compression in the solar wind generated when a fast solar wind stream interacts with a slower leading stream. Our work suggests that the appearance of omega bands is driven by this compression. Key Points: A statistical analysis of 28 omega band events shows that they are driven by extended periods of enhanced solar wind density19 of the 28 omega band events studied occurred during documented stream interaction region events in the solar windAnalysis of the flow speed during all 28 events indicate that omega bands are driven by compression regions rather than high speed streams [ABSTRACT FROM AUTHOR]

The phenomenon known as strong thermal emission velocity enhancement (STEVE) is a narrow optical structure that may extend longitudinally for thousands of kilometers. Initially observed by amateur photographers, it has recently garnered researchers' attention. STEVE has been associated with a rapid westward flow of ions in the ionosphere, known as subauroral ion drift (SAID). In this work, we investigate three occurrences of STEVE, using data from one of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) ground-based all-sky imagers (ASIs) located at Pinawa, Manitoba, and from the Super Dual Auroral Radar Network (SuperDARN). This approach allows us to verify the correlation between STEVE and SAID, as well as analyze the temporal variation of SAID observed during STEVE events. Our results suggest that the SAID activity starts before the STEVE, and the magnitude of the westward flow decreases as the STEVE progresses toward the end of its optical manifestation. [ABSTRACT FROM AUTHOR]

The hyperspectral camera for auroral imaging (HySCAI), which can provide a two-dimensional (2D) aurora image with full spectrum, was developed to study auroral physics. HySCAI consists of an all-sky lens, monitor camera, galvanometer scanner, grating spectrograph, and electron multiplying charge coupled device (EM-CCD). The galvanometer scanner can scan a slit image of the spectrograph on the all-sky image plane in the direction perpendicular to the slit. HySCAI has two gratings; one is 500 grooves/mm for a wide spectral coverage of 400–800 nm with a spectral resolution (FWHM) of 2.1 nm, and the other is 1500 grooves/mm for a higher spectral resolution of 0.73 nm with a narrower spectral coverage of 123 nm. The absolute sensitivity is 2.1 count/s/R with 4 × 4 binning (256 × 340 image) at 557.7 nm. The exposure time depends on the brightness of the aurora emission and is typically 64 s for a 2D image (0.2 s per line scan). This system has been installed at the KEOPS (Kiruna Esrange Optical Platform Site) of the SSC (Swedish Space Corporation) in Kiruna, Sweden. All-sky images with a liquid crystal filter and a sky color camera have also been installed to compensate for the poor time resolution of HySCAI. 2D aurora monochromatic images for given wavelength are obtained by reconstructing the EM-CCD image over the scan period. HySCAI has the advantage of providing a 2D image of intensity for a weak emission line, which appears on top of a high background emission without the contamination from other emissions, which is usually difficult in a system with a bandpass filter. As the first light results, monochromatic images of N 2 + 1NG (0, 1) (427.8 nm), N 2 + 1NG (0, 2) (470.9 nm), H β (486.1 nm), N II (500.1 nm), N I ( 2 D) (520.0 nm), O I ( 1 S) (557.7 nm,), NaD (589.3 nm), O I ( 1 D) (630.0 nm), and N 2 + 1NG (670.5 nm) emission intensity were measured. We estimated the precipitating electron energy from a ratio of I(630.0 nm)/I(427.8 nm) to be 1.6 keV. [ABSTRACT FROM AUTHOR]

In the autumn of 2021, a multichannel imaging photometer of the Pulsating Aurora Imaging Photometer System was installed at the Verkhnetulomsky Observatory. During the first season of operation (2021/2022), measurements were made over the course of 163 nights in three modes of temporal resolution: 2.5 μs, 320 μs, and 41 ms. The high temporal resolution makes it possible to investigate the fine temporal structure of the emission, which are short (less than 1 s) bursts of UV radiation, so-called "microbursts" that can be single or follow in series. The long-term series of microbursts registered on November 27–29, 2021, were analyzed. It is shown that the series of bursts have a complex temporal structure, individual bursts have several peaks with intervals of 100–400 ms, the intervals between bursts are of the order of 1 s, and they appear in packs lasting from several seconds to minutes. The series appear both in quiet geomagnetic conditions and during substorms; the frequency and amplitude of bursts in the second case are significantly larger. [ABSTRACT FROM AUTHOR]

Using two separate databases of in situ ionospheric observations, we present case studies and perform a statistical investigation of the link between energetic precipitating particles during the polar night and high-latitude F-region steepening density spectra. Our study covers approximately 3 years of data obtained near the peak of the 24th solar cycle from four Defense Meteorological Satellite Program satellites and from the European Space Agency's Swarm satellites. Focusing on the midnight sector of the auroral oval, we found that there is a near-perfect co-location between high-energy precipitating particles and occurrence of dissipating F-region plasma density spectra. This is because the precipitating energy flux strongly enhances the E-region Pedersen conductivity, allowing fast and efficient dissipation of kilometer-scale F-region irregularities. Spectra that are possibly non-dissipating are in turn co-located with the distribution of soft electron precipitation. Together, dissipating and non-dissipating density spectra constitute two distinct irregularity regimes. Surprisingly, we also found that efficient dissipation notwithstanding, high-energy precipitating particles cause a net increase in the F-region irregularity power, suggesting that growth and dissipation are interlinked and that some of the observed F-region irregularities may conceivably be generated in the E region. This work is expected to be beneficial for the classification of F-region in situ density spectra and suggests that such density spectra can be used to infer the presence of high-energy or low-energy precipitations based on spectral properties. [ABSTRACT FROM AUTHOR]

Surface, aircraft, and satellite measurements indicate pervasive early cold season (Augut–September) CO2 emissions across Arctic regions, consistent with increased ecosystem metabolism in plants and soils. A key remaining question is whether cold season sources will become large enough to permanently shift the Arctic into a net carbon source. Polar orbiting GHG satellites provide robust estimation of regional carbon budgets but lack sufficient spatial coverage and repeat frequency to track sink‐to‐source transitions in the early cold season. Mission concepts such as the Arctic Observing Mission (AOM) advocate for flying imaging spectrometers in highly elliptical orbits (HEO) over the Arctic to address sampling limitations. We perform retrieval and flux inversion simulation experiments using the AURORA mission concept, leveraging a Panchromatic imaging Fourier Transform Spectrometer (PanFTS) in HEO. Our simulations demonstrate the potential benefits of increased CO2 sampling for detecting emissions during the early cold season. Plain Language Summary: The Arctic is warming rapidly, leading to an acceleration of carbon exchange across tundra and boreal ecosystems. These changing flows of carbon can be difficult to detect using traditional observing systems. We propose that measurement systems which observe Arctic ecosystems continuously from a quasi‐GEO orbit can more accurately detect these important changes, such that unexpected and dangerous feedbacks to climate warming can be monitored and accounted for. Key Points: The Arctic Fourier Transform Spectrometer Investigation (AURORA) mission concept addresses GHG sampling limitations in the ArcticAURORA uses a highly elliptical orbit (HEO) to increase repeat frequency, and a panchromatic iFTS for SWIR O2 and CO2 bands (0.7–2.5 μm)Simulation experiments show potential benefits of increased sampling frequency for grid scale detection of early cold season CO2 emissions [ABSTRACT FROM AUTHOR]

We report a citizen science‐motivated study on the cause of an unusually bright red aurora as witnessed from Hokkaido, Japan during a magnetic storm on 1 December 2023. The auroral brightness of 5 kR is unusual for the Dst index peak of only −107 nT. In spite of the moderate storm amplitude, the extremely high solar wind density of >50/cc and dynamic pressure of >25 nPa caused the aurora oval extension to 53 magnetic latitudes (L = 2.8). We discuss that the drift loss of the ring current particles across the small‐size magnetopause is important, and Hokkaido was at the right position to see the direct effect of the large particle injection of the storm‐time substorm. Plain Language Summary: Citizen scientists identified an unusually bright red aurora from Hokkaido, Japan during a not‐so‐unusual magnetic storm on 1 December 2023. The large dynamic pressure, driven by large density of >50/cc, contributed to a small magnetopause and the effects observed at such low latitude. The hypothesis of this study is that the loss of ring current particles across the small‐size magnetopause played an important role. Also, we discuss that Hokkaido was at the right position to see the direct effect of storm‐time substorm. Key Points: Unusually bright red aurora was witnessed by citizen scientists from Hokkaido, Japan on 1 December 2023The magnetic storm amplitude was not unusually large, but the solar wind density was high (50/cc)Dynamic pressure and asymmetric evolution of the ring current are important to understand the cause of red‐aurora magnetic storm events [ABSTRACT FROM AUTHOR]

The study of atmospheric emissions from orbit to probe the middle and upper atmosphere of Mars, which started with the Mariner missions, is living a golden era thanks to the European Space Agency (ESA) Mars Express mission and other subsequent missions built upon its success, including the ESA ExoMars Trace Gas Orbiter (TGO) mission. Here we summarize the most relevant information obtained by the analysis of atmospheric emissions data from Mars Express and TGO, about the temperature and density structure, the atmospheric dynamics, the chemistry and the atmospheric escape to space. Mars Express also opened a new field of research on Mars with the discovery of aurorae on the planet. We present here the most outstanding results collected by Mars Express about aurorae. Finally, we also discuss how later measurements by other missions have complemented Mars Express and TGO results, and the potential future developments relevant to this field of research. [ABSTRACT FROM AUTHOR]

This editorial titled "The future of space physics 2022" discusses the efforts of the space physics community in producing white papers for research on space physics, mission programs, and funding. It introduces a research topic called "The Future of Space Physics 2022," which contains 64 publications covering various topics in space physics. The document provides a summary of various concepts for new space missions in the field of heliophysics, including studying mesoscale dynamical structures in the solar wind and exploring the interaction between the heliosphere and the interstellar medium. It also emphasizes the importance of diversity and inclusion in the space community, the role of data science and computer simulations in heliophysics research, and the potential of citizen science in advancing space-physics research. The authors express their hope for the future of the heliophysics field and acknowledge the contributions of various individuals and organizations. [Extracted from the article]

The variation in key parameters of the solar–terrestrial space during two consecutive auroral disturbances (the magnetic storm index, Dst index = −422 nT) that occurred during the 18–23 November 2003 period was analyzed in this paper, as well as the spatiotemporal characteristics of NO 5.3 μm radiation with an altitude around the location of 55°N 160°W. The altitude was divided into four regions (50–100 km, 100–150 km, 150–200 km, and 200–250 km), and it was found that the greatest amplification occurs at the altitude of 200–250 km. However, the radiance reached a maximum of 3.38 × 10−3 W/m2/sr at the altitude of 123 km during the aurora event, which was approximately 10 times higher than the usual value during "quiet periods". Based on these findings, the spatiotemporal variations in NO 5.3 μm radiance within the range of latitude 51°S–83°N and longitude of 60°W–160°W were analyzed at 120 km, revealing an asymmetry between the northern and southern hemispheres during the recovery period. Additionally, the recovery was also influenced by the superposition of a second auroral event. The data used in this study were obtained from the OMNI database and the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) infrared radiometer onboard the TIMED (Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics) satellite. Finally, the correlation of NO 5.3 μm radiance at 120 km with temperature, solar wind speed, auroral electrojet index (AE index), and Dst index were analyzed. It was found that only the Dst index had a good correlation with the radiance value. Furthermore, the correlation between the Dst index and radiance at different altitudes was also analyzed, and the highest correlation was found at 170 km. [ABSTRACT FROM AUTHOR]

Pulsating aurora, which consists of diffuse patches blinking on and off, is caused by pitch angle scattering of radiation belt electrons into the loss cone by lowerband chorus waves. Understanding the drivers of pulsating aurora is important as it is a long-lasting and widespread phenomenon, accounting for significant energy transfer from the solar wind into the ionosphere. Substorm injections, which transport electrons from the magnetotail into the inner magnetosphere, are one source of electrons in this region. Injections have been observed simultaneously with pulsating aurora during conjunctions between ground cameras and satellites. In addition, previous work has also shown that substorms can enhance chorus activity (the fundamental process that produces pulsating aurora), providing a mechanism linking substorms to pulsating aurora. To further study this connection, we used the Van Allen Probes and all-sky cameras to look at events where pulsating aurora and substorm injections were observed at different locations in Magnetic Local Time (MLT), rather than focusing only on conjunctions. To make this comparison, we calculated the drift rate of electrons originating from observed injections and projected their motion forward in time until their Magnetic Local Time was the same as the ground camera. When the electrons are located at the same MLT as the ground camera, the pulsating aurora they cause would most likely occur in the field of view of the camera. We compared the time drifting substorm-injected particles arrived at the MLT of the camera to when pulsating aurora was observed. We found several instances where the initiation or intensification of pulsating aurora was accompanied by the arrival of substorm-injected electrons. This observation gives further evidence that pulsating aurora can be enhanced by or occur after substorm injections. [ABSTRACT FROM AUTHOR]

Pulsating aurora, which consists of diffuse patches blinking on and off, is caused by pitch angle scattering of radiation belt electrons into the loss cone by lower-band chorus waves. Understanding the drivers of pulsating aurora is important as it is a long-lasting and widespread phenomenon, accounting for significant energy transfer from the solar wind into the ionosphere. Substorm injections, which transport electrons from the magnetotail into the inner magnetosphere, are one source of electrons in this region. Injections have been observed simultaneously with pulsating aurora during conjunctions between ground cameras and satellites. In addition, previous work has also shown that substorms can enhance chorus activity (the fundamental process that produces pulsating aurora), providing a mechanism linking substorms to pulsating aurora. To further study this connection, we used the Van Allen Probes and all-sky cameras to look at events where pulsating aurora and substorm injections were observed at different locations in Magnetic Local Time (MLT), rather than focusing only on conjunctions. To make this comparison, we calculated the drift rate of electrons originating from observed injections and projected their motion forward in time until their Magnetic Local Time was the same as the ground camera. When the electrons are located at the same MLT as the ground camera, the pulsating aurora they cause would most likely occur in the field of view of the camera. We compared the time drifting substorm-injected particles arrived at the MLT of the camera to when pulsating aurora was observed. We found several instances where the initiation or intensification of pulsating aurora was accompanied by the arrival of substorm-injected electrons. This observation gives further evidence that pulsating aurora can be enhanced by or occur after substorm injections. [ABSTRACT FROM AUTHOR]

In this study, we explore the evolution of long-duration transpolar arcs observed during an exceptionally quiet period by the Fengyun-3D and Defense Meteorological Satellite Program satellites on 17 January 2019. Leveraging the extensive field of view of WAI, we captured the complete structure and evolution of the TPA over a very quiet period exceeding 7 h, with AE<30 nT. The TPA initially manifested at the poleward boundary of the auroral oval in the dawn sector, gradually migrating towards the dusk as the y-component of the interplanetary magnetic field (IMF BY) transitioned from negative to positive. Throughout this phase, the TPA underwent a distortion, transforming from a straight line to an "l-shape". Following a reversal in interplanetary magnetic field BY to negative, the TPA retraced its path towards dawn and ultimately dissipated when the IMF turned southward. Of particular interest is the observation that when the TPA approached the noon-midnight line, small-scale spiral structures became apparent within the TPA. This suggests the presence of intricate small-scale magnetic field topologies or plasma instabilities/shears in the source region. These observations highlight the likelihood of complex field and particle dynamics in the high-latitude reconnection region and the twisted tail plasma sheet. [ABSTRACT FROM AUTHOR]

This study presents a first simultaneous observation of N 2 + Meinel (0,0) band (hereafter, N 2 + (M)) aurora by cutting-edge short-wavelength infrared imaging spectrograph (NIRAS-2) and monochromatic camera (NIRAC) installed at the Kjell Henriksen Observatory (78 ∘ N, 16 ∘ E). On January 21 2023, N 2 + (M) intensification that is associated with a band-shape aurora structure was observed by the NIRAS-2 and the NIRAC having temporal resolutions of 30 s and 20 s, respectively. In addition, the European incoherent scatter Svalbard Radar also observed electron density variations at the same time. Electron density measured at altitude range from 100 km 120 km shows similar variations as of N 2 + (M) intensity, which implies that a primary source of N 2 + (M) emissions is direct collisions of N 2 by precipitating electrons penetrating down to around 100 km altitude (up to 10 keV). However, the observation also demonstrated moderate correlations between N 2 + (M) intensity and electron density above 140 km, which implies that different N 2 + (M) generation process, N 2 charge exchange with O + , may work up to near 160 km and make a non-negligible contribution to N 2 + (M) emissions. This hypothesis would be verified with further radar observations or stereo imaging observations useful to estimate the vertical distribution of the emission layers. The N 2 + (M) is a very promising target wavelength for aurora observation because the quality of sensors is highly expected to improve further and further. Continuous observations with our new instruments will undoubtedly provide an important information of N 2 + (M) characteristics, for future missions of both balloon-borne and satellite-borne imaging. [ABSTRACT FROM AUTHOR]

The South Atlantic Anomaly (SAA) refers to a region where the strength of the magnetic field is notably weaker compared to a dipole field. While previous studies have primarily focused on its effects on the inner radiation belt, this study investigates its impact on the aurora system. By analyzing 2 years' worth of data obtained by the Fengyun‐3E/ACMag instrument, we discover that magnetic fluctuations within the auroral oval are significantly weaker in the longitude sector corresponding to the SAA, as compared to those outside this area. This characteristic remains permanent and independent of seasons and geomagnetic activities. Additional investigation using Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager (DMSP/SSUSI) observations reveals a similar phenomenon in the auroral intensity. Therefore, our results demonstrate that the SAA substantially weakens the aurora system, shedding new light on the effects of magnetic anomalies on planetary auroras and magnetosphere‐ionosphere‐thermosphere coupling. Plain Language Summary: The South Atlantic Anomaly (SAA) is a unique location on Earth where the magnetic field is weaker than normal. This region has drawn a lot of attention because its weakened magnetic field brings the inner Van Allen radiation belt unusually close to the Earth's surface, which poses a threat to satellites passing through it. Here, we uncovered another interesting aspect of the SAA: its impact on the aurora system. To investigate this, we first examined 2 years' worth of data from the ACMag instruments on the Fengyun‐3E satellite, which orbits the Earth at an altitude of 836 km in a dawn‐dusk, Sun‐synchronous orbit. Our findings reveal that the magnetic fluctuations within the southern auroral oval are significantly weaker in the region that aligns with the SAA. This weakening effect is consistently present, regardless of the season or the level of geomagnetic activity. To reinforce our results, we also analyzed auroral intensity from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instrument on the Defense Meteorological Satellite Program (DMSP) satellite, and it corroborated the same weakening trend in this data set. In conclusion, our observations demonstrate that the SAA has a substantial impact on weakening the aurora system. This discovery deepens our understanding of how magnetic anomalies can influence planetary auroras. Key Points: The effects of the South Atlantic Anomaly (SAA) on the terrestrial aurora system are examined using multiple instrumentsObservations reveal a substantial weakening of auroral magnetic fluctuations and auroral intensity in the SAA longitude sectorThe results indicate considering magnetic anomalies like the SAA is essential for comprehensively understanding planetary aurora systems [ABSTRACT FROM AUTHOR]

This study presents a first simultaneous observation of N 2 + Meinel (0,0) band (hereafter, N 2 + (M)) aurora by cutting-edge short-wavelength infrared imaging spectrograph (NIRAS-2) and monochromatic camera (NIRAC) installed at the Kjell Henriksen Observatory (78 ∘ N, 16 ∘ E). On January 21 2023, N 2 + (M) intensification that is associated with a band-shape aurora structure was observed by the NIRAS-2 and the NIRAC having temporal resolutions of 30 s and 20 s, respectively. In addition, the European incoherent scatter Svalbard Radar also observed electron density variations at the same time. Electron density measured at altitude range from 100 km 120 km shows similar variations as of N 2 + (M) intensity, which implies that a primary source of N 2 + (M) emissions is direct collisions of N 2 by precipitating electrons penetrating down to around 100 km altitude (up to 10 keV). However, the observation also demonstrated moderate correlations between N 2 + (M) intensity and electron density above 140 km, which implies that different N 2 + (M) generation process, N 2 charge exchange with O + , may work up to near 160 km and make a non-negligible contribution to N 2 + (M) emissions. This hypothesis would be verified with further radar observations or stereo imaging observations useful to estimate the vertical distribution of the emission layers. The N 2 + (M) is a very promising target wavelength for aurora observation because the quality of sensors is highly expected to improve further and further. Continuous observations with our new instruments will undoubtedly provide an important information of N 2 + (M) characteristics, for future missions of both balloon-borne and satellite-borne imaging. [ABSTRACT FROM AUTHOR]

Flow channels can extend across the polar cap from the dayside to the nightside auroral oval, where they lead to localized reconnection and auroral oval disturbances. Such flow channels can persist within the polar cap >1V2 hours, can move azimuthally with direction controlled by IMF By, and may affect time and location of auroral oval disturbances. We have followed a polar cap arc as it moved duskward from Canada to Alaska for -2 h while connected to the oval. Two-dimensional ionospheric flows show an adjacent flow channel that moved westward with the arc and was a distinct feature of polar cap convection that locally impinged upon the outer boundary of the auroral oval. The flow channel's interaction with the oval appears to have triggered two separate substorms during its trip across western Canada and Alaska, controlling the onset location and contributing to subsequent development of substorm activity within the oval. The first substorm (over Canada) occurred during approximately equatorward polar cap flow, whereas the second substorm (over Alaska) occurred as the polar cap arc and flow channel bent strongly azimuthally and appeared to "lay down" along the poleward boundary. The oval became unusually thin, leading to near contact between the polar cap arc and the brightening onset auroral arc within the oval. These observations illustrate the crucial role of polar cap flow channels in the time, location, and duration of space weather activity, and the importance of the duration and azimuthal motion of flow channels within the nightside polar cap. [ABSTRACT FROM AUTHOR]

This article is an editorial that discusses the current state of space physics and the open questions that still exist in the field. It highlights the progress that has been made in understanding various aspects of space, such as planetary magnetospheres, the solar environment, and the interstellar medium. The editorial also introduces a research topic that includes 17 papers addressing different space physics issues, ranging from wave-particle interactions to the coupling of the Sun and Earth's atmosphere. The goal of this research topic is to assess the state of space physics, identify outstanding questions, and encourage dialogue among researchers. [Extracted from the article]

This article discusses the ionospheric signatures of magnetic reconnection in Earth's magnetosphere. Magnetic reconnection is the process by which the solar wind interacts with Earth's magnetosphere, resulting in the dissipation of magnetic energy and the occurrence of geomagnetic storms. While there has been progress in understanding the local physics of reconnection, there is still a need to understand how reconnection affects Earth's ionosphere on a global scale. This understanding is important for developing global models of the magnetosphere and for quantifying the energy input into Earth's upper atmosphere. The article presents various observations and analyses that provide insights into the ionospheric signatures of magnetic reconnection, including auroral emission, field-aligned currents, and particle precipitation. These observations will help constrain theories and guide the development of future models of magnetosphere-ionosphere coupling. [Extracted from the article]

The space hurricane is a three‐dimensional magnetic vortex structure with strong flow shears and electron precipitation in the polar cap. This study investigates for the first time how a space hurricane disturbs the polar thermosphere. During the formation and development of the space hurricane, the directional reversal of the horizontal neutral wind and the plasma convection will both be relocated from the poleward auroral oval boundary to the edge of the space hurricane, but the neutral wind responds slower compared to the plasma convection. Strong flow shears in the space hurricane causes enhanced Joule heating in the polar cap, which heats the thermosphere and triggers Atmospheric Gravity Waves (AGWs). Statistical results reveal that significant AGWs mainly are located on the dawnside of the space hurricane, suggesting that the space hurricane plays a significant role in ion‐neutral coupling and generation of polar cap AGWs. Plain Language Summary: The space hurricane is a cyclonic aurora structure over the Earth's polar cap region under northward interplanetary magnetic field condition. It can transfer large amounts of energy and plasma into the polar ionosphere during otherwise extremely quiet geomagnetic times. Joule/Frictional heating due to ion‐neutral collisions plays a key role for the energy budget, resulting in non‐negligible atmospheric disturbances, which may impact the orbits of low‐altitude satellites through enhanced frictional drag. Using in situ observations from the Defense Meteorological Satellite Program satellites and the Gravity Field and Steady‐State Ocean Circulation Explorer satellite, we report the first evidence of a disturbed thermosphere triggered by a space hurricane. The neutral wind shows a slow variation in response to the space hurricane plasma convection. Significant wave‐like thermospheric density and vertical wind disturbances are observed around the space hurricane. Enhanced Joule heating from flow shears inside the space hurricane may be the generator. These findings show that the space hurricane plays a significant role for ion‐neutral coupling in the polar cap region. Key Points: The space hurricane can relocate the reversal of the neutral wind from the auroral oval to the edge of the space hurricaneThe space hurricane can heat the thermosphere and generate Atmospheric gravity waves (AGWs) that disturb the neutral density and vertical windThe space hurricane can significantly enhance polar cap AGW activity in the dawn sector [ABSTRACT FROM AUTHOR]

Discrete aurora are sporadic emissions of light originating in Mars upper atmosphere. We report nadir imaging observations from MAVEN's Imaging UltraViolet Spectrograph which identify the conditions which trigger electron precipitation causing these events. Prior studies have shown that discrete aurora events in the strong crustal magnetic field region in the southern hemisphere are the brightest and most repeatable compared to events occurring outside the region. Our new data set offers a more complete and accurate characterization of aurora in this area. The region of strongest crustal fields is composed of two distinct magnetic regions, with magnetic fields in opposite directions; discrete aurora events trigger in one region after dusk and in the other before dawn. Magnetic reconnection in these two adjacent regions with the draped interplanetary field may open the crustal fields in these regions during opposing local times. Particle precipitation can then cause discrete aurora at the observed times and locations. Plain Language Summary: Mars has a surprising variety of types of aurora, all different from Earth's "northern lights." Mars lacks the familiar high‐latitude aurora because it no longer has the same kind of global magnetic field Earth does. This study examines "discrete aurora" events that occur in region in Mars southern hemisphere that has retained some of the ancient magnetic field. It takes the form of long arcades of magnetic loops that resemble a set of arches. As Mars rotates, these arcades are carried around the planet as the solar wind and its imbedded magnetic field are carried past the planet. We show that when conditions are favorable, the magnetic field locked in the solar wind can interact and "reconnect" with Mars magnetic loops, allowing energetic particles to spiral down the field lines into the atmosphere to cause discrete aurora. Key Points: New data confirm that Mars discrete aurora events occur most frequently near strong crustal fields and vary with local timeAuroral events in adjacent regions with opposite magnetic polarity occur before or after midnight depending on local magnetic field directionMagnetic reconnection between crustal fields and the draped interplanetary field appears to control regional and local time behavior [ABSTRACT FROM AUTHOR]

We compare Hubble Space Telescope observations of Jupiter's FUV auroras with contemporaneous conjugate Juno in situ observations in the equatorial middle magnetosphere of Jupiter. We show that bright patches on and equatorward of the main emission are associated with hot plasma injections driven by ongoing active magnetospheric convection. During the interval that Juno crossed the magnetic field lines threading the complex of auroral patches, a series of energetic particle injection signatures were observed, and immediately prior, the plasma data exhibited flux tube interchange events indicating ongoing convection. This presents the first direct evidence that auroral morphology previously termed "strong injections" is indeed a manifestation of magnetospheric injections, and that this morphology indicates that Jupiter's magnetosphere is undergoing an interval of active iogenic plasma outflow. Plain Language Summary: Auroras, known as the "Northern (or Southern) Lights" on Earth, are spectacular manifestations of energetic processes occurring in the space environment of a planet. The behavior of Jupiter's magnetosphere is dominated by the planet's rapid rotation, along with the centrifugally‐driven outflow of plasma (ionized gas) originating from active volcanoes on the moon Io. A prominent auroral feature on Jupiter has for many years been interpreted as a sign that Jupiter's magnetosphere is undergoing active convection, in which plasma from Io "falls" away from the planet, to be replaced by hot, relatively empty "bubbles" known as injections, moving inward. This feature comprises prominent patches of bright emission that are often observed in Jupiter's auroras, though the evidence associating them with injections has been largely circumstantial. Here we show that the NASA Juno spacecraft flew through such injections in the equatorial magnetosphere on magnetic field lines mapping to a cluster of auroral patches as observed by HST. The Juno data also indicated the interval was characterized by signatures of convection and outflow of plasma originating from Io. This demonstrates that auroral patches are signatures of injections, and that auroral emissions are an important tool for diagnosing the behavior of planetary magnetospheres. Key Points: Bright FUV auroral patches on Jupiter are associated with magnetospheric injections and magnetospheric convectionHubble Space Telescope and Juno equatorial data show a cluster of patches is magnetically conjugate with energetic particle injectionsThe interval also exhibits flux tube interchange and lagging magnetic field associated with plasma mass outflow [ABSTRACT FROM AUTHOR]

Poleward Moving Auroral Forms (PMAFs) are one of the most common dayside auroral phenomena and are important for the study of dayside auroras and their dynamical processes. Accurate recognition and localization of PMAFs from a large number of all‐sky imager observations is the first critical step in PMAFs study, but is very difficult and tedious. This paper proposes an integrated model, namely RL‐PMAFs, for automatically recognizing whether an all‐sky auroral video contains PMAFs and, for the first time temporally locating PMAFs. RL‐PMAFs consists of a recognition network and a localization network. Taking the all‐sky auroral videos as input, the recognition network characterizes the morphology and motion of the aurora to determine whether the input videos contain PMAFs. Then, the feature sequences of the videos containing PMAFs are fed to the localization network to obtain the starting and ending times of PMAFs. RL‐PMAFs is evaluated using auroral observations at Arctic Yellow River Station from 2005 to 2007. RL‐PMAFs not only yields higher recognition accuracy of 91.67% than previous methods, but also achieves a precision of 81.90% and a recall of 79.62% for locating PMAFs in auroral videos. The experimental results show that it is a valuable attempt of artificial intelligence for space physics. Plain Language Summary: The All‐Sky Imager (ASI) is a common tool for ground‐based auroral observations that captures the morphology, spectrum, and motion of auroras. Accurately selecting auroral events of interest from the large number of ASI observations is the key for auroral study, but manual processing is extremely tedious. Based on the advanced artificial intelligence technique, this article proposes a PMAFs recognition and localization model (termed RL‐PMAFs) with full consideration of the morphology and motion of PMAFs. As far as we know, this is the first study of PMAFs temporal localization. The experimental results show that it is a valuable attempt of artificial intelligence for auroral physics. Moreover, our method can be easily extended to the recognition and localization of other typical auroral events (e.g., auroral substorms and throat auroras). Key Points: PMAFs are automatically recognized from all‐sky auroral videos and their occurrence times are determined for the first timeWe achieve a recognition accuracy of 91.67% and a temporal localization precision of 81.90% respectivelyOur method can be readily extended to the recognition and localization of other typical auroral events (e.g., auroral substorms) [ABSTRACT FROM AUTHOR]

Continuous observations at specified locations and chronicling of astronomical phenomena provide a good opportunity to study ancient space weather. There are 248 white, 125 red, and 44 blue color aurora-like descriptions, also known as aurora candidates, recorded in Chinese official historical records during the 1365-year period of 511–1876. Qualitative descriptions of the color, location, and appearance time of these candidates are quantitatively denoted. The red, white, and blue aurora candidates occurred most frequently 34% in autumn, 32% in summer, and 49% in summer, respectively. The white and red aurora as well as the overall candidates tend to appear during high solar activity periods. By contrast, the blue candidates frequently occur during low solar activity periods. Statistical results with 90% confidence intervals further show that the relationship between solar activities and overall/red (white/blue) aurora candidates is significant (insignificant). The red aurora candidates that frequently occurred in autumn during the periods of high solar activity agree well with those of low/middle latitude auroras, while the white aurora candidates might be confounded by noctilucent clouds or other atmospheric optical events, such as airglows, moon halo, etc. The study of ancient space weather/climate based on historical records shows that aurora occurrences are related to solar activities, and in particular, red auroras frequently appear in low/middle latitudes during high solar activity periods. [ABSTRACT FROM AUTHOR]

Conjunction observations of auroras with electron distributions and broadband electrostatic fluctuations on Van Allen Probe A satellite in the equatorial region are considered. Using triangulation measurements, the energy spectra of the precipitating electrons in the rayed auroral structures were determined for the 17 March 2015 event. A comparison of the spectra of precipitating electrons in the auroral rays with satellite measurements of electrons in the equatorial region related to the aurora showed their agreement. The concomitance between Van Allen Probe A broadband electric waves and auroral variations measured by the ground-based auroral camera was observed on 17 March 2015. This suggests that broadband electrostatic waves may be responsible for electron precipitation, leading to the formation of rayed structures in the aurora. [ABSTRACT FROM AUTHOR]

Jupiter's auroral emission is a spectacular phenomenon that provides insight into energy release processes related to the coupling of its magnetosphere and ionosphere. This energy release is influenced by solar wind conditions. Using joint observations from Juno and the Hubble Space Telescope (HST), we statistically investigate the relationship between auroral power and current sheet variations under different solar wind conditions. In this study, we reveal that during global main auroral brightening events that are closely connected to solar wind compressions, the dawn side current sheet is substantially thinner than during times when a quiet auroral morphology is present. Furthermore, the total current intensity in the current sheet is found to increase under solar wind compression conditions compared to the quiet period. These findings provide important observational evidence for how magnetospheric dynamics driven by solar wind behavior affect auroral activity, deepening our understanding of the coupling between Jupiter's magnetosphere and ionosphere. Plain Language Summary: Jupiter, the largest planet in our solar system, has a fascinating and powerful auroral emission that can help us understand the interactions between its magnetic field and the charged particles in its atmosphere. These auroral emissions are influenced by solar wind conditions, which are streams of charged particles coming from the Sun. In this study, we used observations from the Juno spacecraft and the Hubble Space Telescope to investigate the relationship between Jupiter's auroral emissions and changes in the planet's magnetic field. We found that during periods of increased solar wind pressure, the magnetic field layer, known as the current sheet, becomes thinner compared to times when the aurora is quiet. These findings offer valuable evidence of how Jupiter's magnetic field is affected by solar wind behavior and improve our understanding of the relationship between the planet's magnetic field and its aurora. This research helps us better comprehend the complex processes occurring in Jupiter's magnetosphere and can potentially enhance our knowledge of similar phenomena occurring on other planets. Key Points: The features of the current sheet in Jupiter's dawnside magnetosphere are highly relevant to auroral contextsDuring a solar wind compression event, the dawnside current sheet becomes substantially thinner than during quiet timesThe total current intensity of the current sheet is much higher during solar wind compression events than the quiet times [ABSTRACT FROM AUTHOR]

The Atmospheric Infrared Sounder (AIRS) instrument onboard the NASA Aqua satellite is used to observe aurora associated with the CO2 4.26 μm emission. These observations are due to non‐local thermodynamic equilibrium (NLTE) resulting from the vibrational excitation of CO2, which arises in the process of auroral energetic particle precipitation, as opposed to the dayside NLTE occurring due to solar radiation. The observations are confirmed to be associated with aurora using the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) limb measurements and the SuperMAG Electrojet (SME) index. The high spectral resolution and low noise associated with the AIRS instrument allows for the emission spectrum to be calculated and confirmed to arise from CO2. Our new NLTE index values derived from AIRS provide the ability to globally measure auroral events associated with CO2 with a spatial resolution on the order of ∼13.5 km. Plain Language Summary: The aurora are caused by energetic particle precipitation into Earth's atmosphere due to energy buildup and release in Earth's magnetic field from interaction with the solar wind. These energetic particles smash into Earth's atmosphere with high energy, and react with atoms and molecules in the atmosphere. There are many types of emissions of light that are associated with Earth's aurora. One of these emissions is the infrared emission centered near 4.26 μm associated with excited CO2 molecules. When CO2 is vibrationally excited through an exchange of energy with an N2 molecule excited by auroral particles, the CO2 molecule eventually relaxes from this state and releases a photon near 4.26 μm. This research presents a satellite observation from NASA's AIRS instrument allowing for the CO2 auroral emission to be viewed and mapped from space. Key Points: A carbon dioxide infrared emission at 4.26 microns associated with the aurora is observed by the Atmospheric Infrared Sounder (AIRS) instrumentA new non‐local thermodynamic equilibrium index provides a quantitative measure of the carbon dioxide auroral‐associated emissionThe AIRS auroral observations are confirmed by simultaneous Sounding of the Atmosphere using Broadband Emission Radiometry measurements and the SuperMAG Electrojet index [ABSTRACT FROM AUTHOR]

Juno's highly inclined orbits provide opportunities to sample high‐latitude magnetic field lines connected to the orbit of Io, among the other Galilean satellites. Its payload offers both remote‐sensing and in‐situ measurements of the Io‐Jupiter interaction. These are at discrete points along Io's footprint tail and at least one event (12th perijove) was confirmed to be on a flux tube Alfvénically connected to Io, allowing for an investigation of how the interaction evolves down‐tail. Here we present Alfvén Poynting fluxes and field‐aligned current densities along field lines connected to Io and its orbit. We explore their dependence as a function of down‐tail distance and show the expected decay as seen in UV brightness and electron energy fluxes. We show that the Alfvén Poynting and electron energy fluxes are highly correlated and related by an efficiency that is fully consistent with acceleration from Alfvén wave filamentation via a turbulent cascade process. Plain Language Summary: Io and Jupiter are electrodynamically coupled resulting in the Io footprint tail. This is one of the most persistent, stable, and recognizable features of Jupiter's aurora. The Juno spacecraft routinely samples magnetic field lines connected to Io's orbit, allowing for an investigation of this powerful coupling. We use data recorded by Juno to estimate a proxy for the strength of this interaction, that is, electromagnetic energy, and show its dependence downstream of Io and how the interaction decays. We further show that the available electromagnetic energy and electron energy are intimately linked, suggesting a transfer of energy between wave and particles. This is the basis upon which electrons end up precipitating into Jupiter's upper atmosphere and generate some of the brightest auroras. Key Points: Alfvénic Poynting fluxes and electron energy fluxes are highly correlated on magnetic field lines connected to Io's orbitThe efficiency in the Main Alfvén Wing is ∼10%, fully consistent with Alfvén wave filamentation via a turbulent cascade processField‐aligned current densities are quantified and exhibit a decay in magnitude down‐tail of Io [ABSTRACT FROM AUTHOR]

Ion drag associated with the ionospheric plasma convection plays an important role in the high-latitude thermospheric dynamics, yet changes in the thermospheric wind with geomagnetic activity are not fully understood. We performed a statistical analysis of the thermospheric wind measurements with a Fabry–Perot interferometer (FPI; 630 nm wavelength) in Tromsø, Norway, in the winter months for 9 years. The measurements were sorted by a SuperMAG (SME) index, and a quiet-time wind pattern was defined as an hourly mean under SME ≤ 40 nT. The quiet-time wind pattern can be expected to be represented by a pressure gradient associated with the solar radiation and a geostrophic force balance. With an increase in the geomagnetic activity level, the thermospheric wind turned over from eastward to westward at dusk and increased the equatorward magnitude from midnight to dawn. Deviations from the quiet-time wind presented similar patterns in the direction with the ionospheric plasma convection but were larger in magnitude at dusk than at dawn. This is the first study to report a dawn-dusk asymmetry of the thermospheric wind acceleration feature and signatures of the eastward wind acceleration at dawn by ion drag. [ABSTRACT FROM AUTHOR]

Alfven-branch waves provide an efficient means for transporting energy into the auroral oval. Here, we report observations of these waves obtained by the Fengyun-3E (FY-3E)/ACMag instruments, which are designed to detect three-dimensional AC magnetic fields in the 0.05–25 Hz band. The observations suggest that broadband waves are a permanent feature of the auroral oval, although their amplitude and locations vary with the global state of the magnetosphere. We primarily focus on the data obtained from 10 July 2021 to 26 August 2021, during which a series of recurrent storms driven by solar wind corotating interaction regions (CIRs) occurred. Analysis of the observations shows that the auroral-oval waves grow in amplitude (1–3 orders of magnitude) and shift to lower latitude (∼10°) immediately following the decrease in the SYM-H index in each storm. Further investigation reveals the response of the auroral-oval waves has a time scale equal to or less than FY-3E's effective revisiting time, which is about 45 min. The observations presented in this paper confirm that the FY-3E/ACMag instruments provide a high-resolution monitor of the auroral-oval waves and could further our understanding of auroral physics. [ABSTRACT FROM AUTHOR]

Aurora is an important manifestation of solar‐terrestrial physical processes. The aurora activities have rapid changes in spatial and intensity distribution during a substorm, especially the expansion phase. In this paper, a newly developed aurora evolution model is built based on the Convolutional Long Short‐Term Memory network, using the aurora images captured by the ultraviolet imager on the Polar satellite during the substorm expansion phases. Given the images after the onset, the model can predict the evolution of aurora with reasonable accuracy. The structure similarity, Peak Signal‐to‐Noise Ratio (Peak Signal to Noise Ratio), and Root Mean Square Error are used to evaluate the similarity between the predicted and observed images. The results demonstrate that the model performs well at different scales of evolution. Additionally, the model can estimate the evolution of both the aurora intensities and the movement of the poleward boundary. Furthermore, three cases are displayed to illustrate the behavior of the model and its limitation. Plain Language Summary: Earth is surrounded by magnetic field and particles. The near‐Earth environment is not always quiet, which is strongly affected by the sun. As the most representative manifestation of solar‐terrestrial physical processes, the aurora grows and evolves rapidly when strong space weather occurs, such as the substorm. To have a better grasp of the aurora evolution during the substorm expansion phase, we developed a deep learning model based on the Polar/ultraviolet imager aurora images. The testing results demonstrated that, given the observed aurora images in the early stage of the substorm expansion phase, the model can accurately predict the dynamic evolution of global aurora patterns and intensity distribution. Key Points: An aurora evolution prediction model was built based on Convolutional Long Short‐Term Memory networkThe model can predict the evolution of the aurora using the previous aurora images during the substorm expansion phaseThe total aurora intensity, as well as the poleward boundaries, can be accurately predicted [ABSTRACT FROM AUTHOR]

Terrestrial auroras are highly structured that visualize the perturbations of energetic particles and electromagnetic fields in Earth's space environments. However, the identification of auroral morphologies is often subjective, which results in confusion in the community. Automated tools are highly valuable in the classification of auroral structures. Both CNNs (convolutional neural networks) and transformer models based on the self-attention mechanism in deep learning are capable of extracting features from images. In this study, we applied multiple algorithms in the classification of auroral structures and performed a comparison on their performances. Trans-former and ConvNeXt models were firstly used in the analysis of auroras in this study. The results show that the ConvNeXt model can have the highest accuracy of 98.5% among all of the applied algorithms. This study provides a direct comparison of deep learning tools on the application of classifying auroral structures and shows promising capability, clearly demonstrating that auto-mated tools can help to minimize the bias in future auroral studies. [ABSTRACT FROM AUTHOR]

Identification of small-scale auroral structures is key to searching for auroral events. However, it is impracticable for humans to manually select sufficient aurora events for statistical analysis, and it is also challenging for computers because of the non-rigid shape and fluid nature of auroras. Fold structure is the most common type of auroral small-scale structure, and its appearance is indicative of a variety of auroral events. This paper proposes a small-scale aurora structure identification framework to automatically detect aurora fold structures. First, the location and shape of auroras are identified based on a deep learning segmentation network. Then, the skeleton of the auroral shape is extracted to represent the trajectories of auroras. Finally, the proposed skeleton-based fold identification module (SFIM) can detect the aurora fold structure. To evaluate the effectiveness of the proposed method, we built an aurora fold structure sample dataset, namely F-dataset, containing 2000 images at 557.7 nm obtained by the all-sky imagers at Yellow River Station (YRS), Ny-Ålesund, Svalbard. Experimental results show that automatic identification can achieve good consistency with human perception. Statistical analysis of over 30,000 images shows that the fold occurrence has a distinct double-peak distribution at pre-noon and post-noon. [ABSTRACT FROM AUTHOR]

This article describes a new understanding of the explosive nature of auroras, called auroral substorms, on the basis of a series of processes, from power supply (dynamo), circuit/current, and dissipation (auroral substorms) – the electric current approach, in which the magnetosphere or more specifically the primary magnetosphere-ionosphere coupling system (the primary M-I system) plays a crucial role. The primary M-I system has an anomaly; it cannot dissipate the dynamo power much for about 1 h after the dynamo power becomes above 1011 w. This anomaly is due to a low conductivity of the quiet-time ionosphere to dissipate increasing power. Thus, the power is accumulated in the inner magnetosphere (at about 6 Re; Re = earth's radius) as magnetic energy, inflating the inner magnetosphere. When the accumulated energy reaches to about 1016 J, the primary M-I system seems to become unstable and unload impulsively the accumulated magnetic energy, deflating the magnetosphere. This deflating process generates the secondly M-I system, which is associated with an electric field 5–50 mV/m and field-aligned currents, ionizing the ionosphere and increasing the conductivity. Therefore, the primary M-I system can perform like an ordinary electrical system. It is this particular nature that exhibits explosive auroral displays. This paper describes systematically and semiquantitatively key points of this series of processes based on a few decades of work. The electric current approach is rather 'new' in substorm research and thus is rudimental at its development stage, so that n crucial issues are mentioned for future studies at the end. [ABSTRACT FROM AUTHOR]

This research leverages data from the Day/Night Band (DNB) of the Visible Infrared Imaging Radiometer (VIIRS) instrument onboard the Suomi National Polar‐orbiting Partnership (S‐NPP) satellite. We demonstrate the value of mining the VIIRS DNB for aurora and describe our use of unsupervised machine learning to create a binary mask for aurora occurrence. This mask can be used to flag aurora‐contaminated observations for NASA's nighttime lights products for Earth science applications. The identification of auroral regions can also be used for Space Weather applications, for example, for comparison with aurora forecast model and with other satellite‐ or ground‐based aurora observations. The DNB is a broadband channel that is sensitive to wavelengths from 500 to 900 nm, which covers most of the visible light spectrum, and as the name implies, captures light even at night with a sensitivity at the nanowatt level. This band is suitable for aurora observations since the light emitted by the aurora tends to be dominated by emissions from atomic oxygen, resulting in a greenish glow at a wavelength of 557.7 nm, especially at an altitude of 110 km. This study compares the global nighttime derived aurora regions for 17 and 18 March with the NOAA Space Weather Prediction Center's (SWPC) probability product for the St. Patrick's Day geomagnetic storm in 2015. VIIRS sensors are slated to be added to the next generation of polar‐orbiting operational satellites. Our novel automated approach to aurora identification opens up an efficient way to leverage this unique data source. Key Points: Aurora can be detected in satellite‐based Earth nighttime lights using unsupervised machine‐learning methodsA binary aurora mask can be derived and used to eliminate aurora‐contaminated nighttime lights observations from analysis for Earth science applicationsThese aurora observations can be used for comparison with aurora forecast model predictions and to augment other sources of aurora observations [ABSTRACT FROM AUTHOR]

On 7 June 2021, Juno‐UVS mapped Ganymede's auroral emissions near a closest approach altitude of 1,046 km. The high spatial resolution map exhibits bright, 200–1,000 R, oxygen emissions organized into northern and southern auroral ovals. Though the map has incomplete global coverage, UVS observed longitudinal structure similar to that described by McGrath et al. (2013), https://doi.org/10.1002/jgra.50122 and latitudinal and vertical structure never before resolved. The mapped auroral emissions (a) display an intense narrow auroral curtain with a sharp poleward boundary, (b) have a more slowly decreasing equatorial edge on the leading hemisphere, (c) appear to originate near the surface with a vertical extent of 25–50 km, and (d) are slightly brighter in the north than the south. Additionally, we present UVS observations from the more distant Juno Ganymede flyby on 20 July 2021. We describe the observations, compare them to previous Hubble Space Telescope observations and current model predictions of the open‐closed‐field line‐boundary. Plain Language Summary: Observations of Ganymede by Juno‐UVS during a close flyby (during Juno's 34th Jupiter orbit) captured unique high‐spatial‐resolution measurements of Ganymede's auroral emissions. Organized into two polar ovals, the positions and intensities of the auroral emissions are consistent with previous Hubble Space Telescope observations. The observed morphology of the auroras on the leading hemisphere of Ganymede exhibits latitudinal structure never before resolved. Previous studies suggest the poleward edge of the emissions trace the poleward most position of the magnetic field lines that have both ends rooted to Ganymede. We show that a magnetic field model of Ganymede within Jupiter's larger magnetosphere predicts last‐closed field‐lines very close to the observed auroral emissions, as expected. More distant observations taken during Juno's following orbit (orbit 35) capture auroral emissions at slightly different longitudes. They too show similar agreement with previous observations and current magnetic field models. Key Points: The high spatial resolution observations revealed auroral emissions of over 1000 Rayleighs, brighter than previously observedThe leading hemisphere aurora exhibits an intense auroral curtain with a sharp poleward boundary and more slowly tapering equatorial edgeJuno‐UVS observed Ganymede's auroral emissions extending up to a maximum of 50 km altitude [ABSTRACT FROM AUTHOR]

The thermospheric wind response to a sudden westward turning of the ion velocity at a high latitude was studied by analyzing data obtained with a Fabry–Perot interferometer (FPI; 630 nm), Dynasonde, and Swarm A & C satellites during a conjunction event. The event occurred during a geomagnetically quiet period (Kp = 0 +) through the night, but some auroral activity occurred in the north. The collocated FPI and Dynasonde measured the thermospheric wind (U) and ionospheric plasma velocity (V), respectively, in the F region at the equatorward trough edge. A notable scientific message from this study is the possible role of thermospheric wind in the energy dissipation process at F-region altitude. The FPI thermospheric wind did not instantly follow a sudden V change due to thermospheric inertia in the F region. At a pseudo-breakup during the event, V suddenly changed direction from eastward to westward within 10 min. U was concurrently accelerated westward, but its development was more gradual than that of V, with U remaining eastward for a while after the pseudo-breakup. The delay of U is attributed to the thermospheric inertia. During this transition interval, U∙V was negative, which would result in more efficient generation of frictional heating than the positive U∙V case. The sign of U∙V, which is related to the relative directions of the neutral wind and plasma drift, is important because of its direct impact on ion-neutral energy exchange during collisions. This becomes especially important during substorm events, where rapid plasma velocity changes are common. The sign of U∙V may be used as an indicator to find the times and locations where thermospheric inertia plays a role in the energy dissipation process. [ABSTRACT FROM AUTHOR]

This document is a collection of research articles that explore the interconnected dynamics of the magnetosphere-ionosphere system. It covers topics such as radiation belts, aurora, current systems, and geomagnetic indices. The studies utilize various methods such as satellite and ground-based data, theory, modeling, simulations, and machine learning to investigate these phenomena. The findings contribute to our understanding of the behavior and dynamics of this complex system. The document also highlights the need for further research in this field and suggests future directions for study. [Extracted from the article]

Proton aurora at Mars are thought to form indirectly, as a result of solar wind proton charge exchange with planetary coronal hydrogen upstream of the bow shock. This charge exchange produces beamed energetic neutral atoms that bypass the induced magnetosphere and cause spatially uniform auroral emission when they collide with the thermosphere. Here we report multiple definitive observations of spatially localized "patchy" proton aurora at Mars using the Emirates Mars Ultraviolet Spectrometer on the Emirates Mars Mission, and characterize the plasma environment during these events using contemporaneous Mars Atmosphere and Volatile EvolutioN mission measurements. Multiple mechanisms are required to explain these observations, including at times the direct deposition of solar wind plasma into the thermosphere, particularly during radial interplanetary magnetic field conditions. Much future work will be needed to assess these mechanisms and understand the impact of these auroral events on Mars atmospheric evolution. Plain Language Summary: Even though Mars does not have a global magnetic field like the Earth, it still possesses multiple kinds of aurora. One of these is proton aurora, which is thought to form mainly by an indirect process that allows a small fraction of the solar wind to rain down on the planet uniformly across the dayside. We present observations of patchy proton aurora at Mars that require a different explanation. By examining multiple Emirates Mars Mission observations of patchy aurora that have different shapes and locations, and combining these images with plasma measurements made by NASA's Mars Atmosphere and Volatile EvolutioN mission, we conclude that a number of processes can produce patchy aurora. This patchy aurora is mostly the result of plasma turbulence, which under some circumstances leads to direct deposition of the solar wind across the entire Martian dayside, with a potentially large impact on long term atmosphere and water loss from Mars. Key Points: We present the first definitive evidence for spatially localized "patchy" proton aurora on MarsSome events support a hypothesis that radial interplanetary magnetic field conditions can produce patchy proton auroraOther events occur during typical solar wind conditions, requiring new formation mechanisms related to sheath plasma turbulence [ABSTRACT FROM AUTHOR]

In recent years, neural networks have been increasingly used for classifying aurora images. In particular, convolutional neural networks have been actively studied. However, there are not many studies on the application of deep learning techniques that take into account the characteristics of aurora images. Therefore, in this study, we propose the use of deep metric learning as a suitable method for aurora image classification. Deep metric learning is one of the deep learning techniques. It was developed to distinguish human faces. Identifying human faces is a more difficult task than standard classification tasks because this task is characterized by a small number of sample images for each class and poor feature variation between classes. We thought that the face identification task is similar to aurora image classification in that the number of labeled images is relatively small and the feature differences between classes are small. Therefore, we studied the application of deep metric learning to aurora image classification. As a result, our experiments showed that deep metric learning improves the accuracy of aurora image classification by nearly 10% compared to previous studies. [ABSTRACT FROM AUTHOR]

We present the first measurements of Mars discrete aurora in the extreme ultraviolet (<110 nm) and the first synoptic aurora images in the far ultraviolet (110–180 nm). Auroral emission is detected in >75% of nightside images, with patterns shifting visibly over 15–20 min. Aurora is observed most frequently in regions of open magnetic topology (where crustal magnetic fields are very weak and/or vertical), with the brightest aurora where crustal fields are strongest. We present the first disk‐averaged spectrum of discrete aurora, with several O, C, and CO features as expected for electron impact primarily on CO2. We categorize discrete auroral morphology into three types: crustal field aurora, non‐crustal field patchy aurora, and a new type we call "sinuous" aurora, an elongated serpentine structure that stretches thousands of kilometers into the nightside from near midnight in the northern hemisphere. These observations point to a highly dynamic environment in Mars' magnetotail. Plain Language Summary: In this study, we present near‐global images of localized aurora on Mars and the first measurements of these aurora at very short ultraviolet wavelengths (<110 nm). They are caused by energetic electrons from the solar wind smashing into Mars' upper atmosphere. We find auroras in >75% of images, with their patterns shifting visibly over 15–20 min. They are observed most frequently in regions where magnetic fields are very weak or both strong and vertical, with the brightest aurora where magnetic fields are strongest. We present the first disk‐averaged spectrum of these auroras, showing features expected for electrons striking CO2 (the most abundant gas in Mars' atmosphere). We categorize discrete auroral patterns into three types: those near strong vertical crustal magnetic field, patchy aurora near very weak crustal fields, and a new type we call "sinuous," an elongated serpentine structure that stretches thousands of kilometers into the nightside from near midnight in the northern hemisphere. These observations point to a highly dynamic environment in Mars' nightside space environment. Key Points: We present the first disk measurements of Mars discrete aurora in the EUV end FUV, with the oxygen feature at 130.4 nm being the brightestAuroras are detected in ∼75% of nightside images and are more likely where crustal fields are either very weak or both strong and verticalAn elongated, sinuous discrete aurora is discovered, extending far into the nightside. It may be related to the magnetotail current sheet [ABSTRACT FROM AUTHOR]

We report computer studies showing how the duration of memory for storage and retrieval of a classical bit can be increased to 100 times the decay time of an isolated atom, with no use of high-tech cold-atom preparations recently developed in the light-matter field. We suggest that our low-tech procedure can greatly enlarge the number of experimenters able to enter this field. The role of symmetry in this procedure arises in a careful interplay of incoherent and coherent excitations of a large collection of "two-level" atoms, the level separation being matched by the dominant frequency of the electromagnetic fields (short pulses and continuing field) applied to the system. [ABSTRACT FROM AUTHOR]

A series of experiments have shown recently that several auroral lines are polarized, when observed from the ground. However, this polarization may be caused by indirect light sources (from the ground or the sky) scattered in the lower atmosphere by Rayleigh and Lorenz‐Mie scattering, or during the crossing of the ionospheric current sheets. Here, we present polarization measurements of the N2+ ${N}_{2}^{+}$ blue (427.8 nm) and purple (391.4 nm) emissions in a laboratory confined setting that excludes any light pollution or scattering. We show that both lines are polarized, at a level comparable to that of the natural auroral observations. Our results furthermore show that the Degree of Linear Polarization depends on the magnetic conditions. This set of experiments confirms in a controlled environment the polarization of auroral emissions and constitutes a strong evidence in favor of auroral emission already polarized in the upper atmosphere. Plain Language Summary: We prove through a laboratory experiment the existence of the auroral polarization. We also show that this polarization is created at the emission itself and not during its travel through the atmosphere. Key Points: We reproduce in confined laboratory conditions the auroral blue and purple ionospheric emissionsThe Degree of Linear Polarization depends on the magnetic conditions and is similar to that observed in the auroraeWe conclude that part of the observed auroral lights polarization is created at the emission [ABSTRACT FROM AUTHOR]

We present 14 simultaneous Chandra X‐ray Observatory (CXO)‐Hubble Space Telescope (HST) observations of Jupiter's Northern X‐ray and ultraviolet (UV) aurorae from 2016 to 2019. Despite the variety of dynamic UV and X‐ray auroral structures, one region is conspicuous by its persistent absence of emission: the dark polar region (DPR). Previous HST observations have shown that very little UV emission is produced by the DPR. We find that the DPR also produces very few X‐ray photons. For all 14 observations, the low level of X‐ray emission from the DPR is consistent (within 2‐standard deviations) with scattered solar emission and/or photons spread by Chandra's Point Spread Function from known X‐ray‐bright regions. We therefore conclude that for these 14 observations the DPR produced no statistically significant detectable X‐ray signature. Plain Language Summary: Jupiter produces the most powerful ultraviolet (UV) and X‐ray aurorae in the solar system. While the UV and X‐ray aurora of the planet have each been explored independently, previous work exploring the spatial connection between Jupiter's X‐ray and UV aurorae was limited to a single simultaneous Chandra X‐ray Observatory (CXO) and Hubble Space Telescope (HST) observation from 2003. Since 2016, the arrival of the Juno spacecraft at Jupiter has led to extensive observing campaigns with CXO and HST, resulting in many new simultaneous X‐ray‐UV observations. Here, we present the analysis of 14 simultaneous CXO and HST observations of Jupiter's Northern aurorae from 2016 to 2019. While much of the emission from these bright aurorae is dynamic, there is one region that is dim for all 14 observations: Jupiter's dark polar region. Previous observations of this region have shown that it produces very little UV light. However, the extent to which X‐ray light is produced by the region remained unexplored and could provide the key to identifying why the region is so dark and what this tells us about the Jovian system. Across these 14 observations, we find that the region produces no significant X‐ray emission. Key Points: We compare 14 simultaneous Chandra X‐ray Observatory and Hubble Space Telescope UV observations of Jupiter's Northern AuroraeWe detect no statistically significant X‐ray emission from the UV dark polar region (DPR)The DPR expands and the X‐ray and UV emission on the swirl region boundary shifts when the aurora show solar wind compression morphology [ABSTRACT FROM AUTHOR]

SGLT2i reduce cardiac hypertrophy, but underlying mechanisms remain unknown. Here we explore a role for serine/threonine kinases (STK) and sodium hydrogen exchanger 1(NHE1) activities in SGLT2i effects on cardiac hypertrophy. Isolated hearts from db/db mice were perfused with 1 µM EMPA, and STK phosphorylation sites were examined using unbiased multiplex analysis to detect the most affected STKs by EMPA. Subsequently, hypertrophy was induced in H9c2 cells with 50 µM phenylephrine (PE), and the role of the most affected STK (p90 ribosomal S6 kinase (RSK)) and NHE1 activity in hypertrophy and the protection by EMPA was evaluated. In db/db mice hearts, EMPA most markedly reduced STK phosphorylation sites regulated by RSKL1, a member of the RSK family, and by Aurora A and B kinases. GO and KEGG analysis suggested that EMPA inhibits hypertrophy, cell cycle, cell senescence and FOXO pathways, illustrating inhibition of growth pathways. EMPA prevented PE-induced hypertrophy as evaluated by BNP and cell surface area in H9c2 cells. EMPA blocked PE-induced activation of NHE1. The specific NHE1 inhibitor Cariporide also prevented PE-induced hypertrophy without added effect of EMPA. EMPA blocked PE-induced RSK phosphorylation. The RSK inhibitor BIX02565 also suppressed PE-induced hypertrophy without added effect of EMPA. Cariporide mimicked EMPA's effects on PE-treated RSK phosphorylation. BIX02565 decreased PE-induced NHE1 activity, with no further decrease by EMPA. RSK inhibition by EMPA appears as a novel direct cardiac target of SGLT2i. Direct cardiac effects of EMPA exert their anti-hypertrophic effect through NHE-inhibition and subsequent RSK pathway inhibition. [Display omitted] • EMPA directly reduces RSK, Aurora A and B kinases in isolated murine diabetic heart. • EMPA inhibits phenylephrine-induced cardiac hypertrophy in H9c2 cells. • EMPA inhibits cell hypertrophy through inhibition of NHE1 and RSK activity. • Direct cardiac effects of EMPA exert anti-hypertrophy through NHE-RSK inhibition. [ABSTRACT FROM AUTHOR]

Jupiter's main auroral emissions usually form auroral curtains surrounding the magnetic poles. Most explanations for this auroral feature are based on corotation enforcement currents flowing between the magnetosphere and the ionosphere. This process predicts the highest emitted power to originate from the dawn region, while the lowest emitted power would come from the noon to dusk region. However, a previous study using Hubble Space Telescope data showed the opposite, with a higher emitted power in the dusk region in the south and ambiguous results in the north. In the present study, we use data from the first 39 Juno perijoves to reexamine this question. We find a dusk region 2.9 to 5.5 times more powerful than the dawn one, in qualitative agreement with the previous study but contrary to theoretical expectations. These results support the idea that the main emissions cannot be fully described by corotation enforcement currents. [ABSTRACT FROM AUTHOR]

Discrete aurorae have been observed at magnetized planets such as Earth and Jupiter, triggered by accelerated electrons. Similar aurorae have also been observed at Mars with only localized strong crustal magnetisms. However, our understanding of this phenomenon at Mars is still limited. In particular, direct and quantitative comparisons of the auroral and its source electron events are lacking as these two types of observations are usually made at different times and/or locations. In this study, we establish empirical criteria to select electron events ("auroral electrons") that could trigger detectable auroral emissions with Mars Atmosphere and Volatile EvolutioN measurements, thereby enabling a direct statistical comparison. We find auroral electrons share similar statistical characteristics to those previously reported for discrete auroral events. This study bridges the gap between electron observations and auroral detections and enables collaborations across different Mars missions, as well as comparative planetary studies of discrete aurora. Plain Language Summary: Aurorae have been observed in the polar regions at magnetized planets such as Earth and Jupiter, triggered by accelerated electrons. Similarly, localized auroral emissions have also been reported at Mars with no global dipole field but localized strong crustal magnetisms. However, our understanding of aurorae at Mars is still very limited in terms of their characteristics and the source electrons. In particular, direct and quantitative comparisons of the auroral and electron events are lacking as these two types of observations are usually made at different times and/or locations because of the limitation of single‐spacecraft observations. This study establishes empirical criteria to select auroral electrons and statistically compare these two types of observations. This study bridges the gap between the electron observations and auroral detections and enables collaborations across different Mars missions, as well as studies of auroral phenomena at different planets. Key Points: We establish empirical criteria to select electron events that could trigger detectable auroral observationsWe find similar statistical behaviors in selected electron events as discrete auroral events and explore the cause of statistical trendsThis study bridges the gap of these two types of observations and motivates collaborations across different Mars missions [ABSTRACT FROM AUTHOR]