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This paper presents the results of analysis of oblique ionospheric sounding data obtained with continuous chirp signal on the subauroral paths Magadan—Irkutsk and Norilsk—Irkutsk. It specifies the interplanetary sources of magnetic storms in November–December 2023. It was established that signals propagating outside the great-circle arc and additional diffuse reflections can be found in oblique sounding ionograms in intense magnetospheric convection field. Their appearance can be related to refraction of radio waves on the polar wall of the main ionospheric trough and scattering by small-scale inhomogeneities. Connection has been revealed between variations in the maximum observed frequencies of HF radio wave propagation modes with the spatial position of the main ionospheric trough and the equatorial boundary of diffuse electron precipitation zone.

The paper examines conditions of occurrence and typical time scales of a polarization jet by measuring ionospheric parameters from DMSP satellites (h~830 km) and using data from the ground-based ionospheric station Yakutsk (YA462) during strong and long-term geomagnetic storms. The polarization jet at the ionospheric station Yakutsk was recorded in the dusk sector at the background of substorm disturbances when the geomagnetic index SME reached values from 1000 to ~3000 nT, and, according to data from the magnetic observatory Yakutsk (YAK), there was a positive bay ~50–100 nT in the geomagnetic field H component and ~100–200 nT in its Z component. We show that the lifetime of the polarization jet or narrow troughs in ionospheric plasma in the subauroral ionosphere during strong and long-term magnetic storms can be as long as 12 hrs.

Solar wind charge exchange (SWCX) is the process of solar wind high-valence ions exchanging charges with neutral components and generating soft X-rays. Recently, detecting the SWCX emission from the magnetosphere is proposed as a new technique to study the magnetosphere using panoramic soft X-ray imaging. To better prepare for the data analysis of upcoming magnetospheric soft X-ray imaging missions, this paper compares the magnetospheric SWCX emission obtained by two methods in an XMM-Newton observation, during which the solar wind changed dramatically. The two methods differ in the data used to fit the diffuse X-ray background (DXB) parameters in spectral analysis. The method adding data from the ROSAT All-Sky Survey (RASS) is called the RASS method. The method using the quiet observation data is called the Quiet method, where quiet observations usually refer to observations made by the same satellite with the same target but under weaker solar wind conditions. Results show that the spectral compositions of magnetospheric SWCX emission obtained by the two methods are very similar, and the changes in intensity over time are highly consistent, although the intensity obtained by the RASS method is about \begin{document}$2.68\,\pm\, 0.56$\end{document} keV \begin{document}${\rm{cm}}^{-2} {\rm{s}}^{-1} {\rm{sr}}^{-1}$\end{document} higher than that obtained by the Quiet method. Since the DXB intensity obtained by the RASS method is about \begin{document}$2.84\,\pm\, 0.74$\end{document} keV \begin{document}${\rm{ cm}}^{-2} {\rm{s}}^{-1} {\rm{sr}}^{-1}$\end{document} lower than that obtained by the Quiet method, and the linear correlation coefficient between the difference of SWCX and DXB obtained by the two methods in different energy band is close to −1, the differences in magnetospheric SWCX can be fully attributed to the differences in the fitted DXB. The difference between the two methods is most significant when the energy is less than 0.7 keV, which is also the main energy band of SWCX emission. In addition, the difference between the two methods is not related to the SWCX intensity and, to some extent, to solar wind conditions, because SWCX intensity typically varies with the solar wind. In summary, both methods are robust and reliable, and should be considered based on the best available options.

Solar Wind Charge eXchange X-ray (SWCX) emission in the heliosphere and Earth's exosphere is a hard to avoid signal in soft X-ray observations of astrophysical targets. On the other hand, the X-ray imaging possibilities offered by the SWCX process has led to an increasing number of future dedicated space missions for investigating the solar wind-terrestrial interactions and magnetospheric interfaces. In both cases, accurate modelling of the SWCX emission is key to correctly interpret its signal, and remove it from observations, when needed. In this paper, we compile solar wind abundance measurements from ACE for different solar wind types, and atomic data from literature, including charge exchange cross-sections and emission probabilities, used for calculating the compound cross-section \begin{document}$ \alpha $\end{document} for the SWCX X-ray emission. We calculate \begin{document}$ \alpha $\end{document} values for charge-exchange with H and He, relevant to soft X-ray energy bands (0.1−2.0 keV) for various solar wind types and solar cycle conditions.

Ultralow-frequency (ULF) waves play an important role in energy transfer within Earth's magnetosphere due to intensive interaction with the surrounding plasma. Previous works have assumed that these waves are strictly divided by polarization into toroidal, when the magnetic field oscillates in the azimuthal direction, and poloidal, when it oscillates in the radial direction. The former are azimuthally large-scale and are excited by external sources, whereas the latter are small-scale and are generated by internal plasma instabilities. Observations show, however, that waves of mixed polarization often occur, and the nature of this mixing has not been explained. In this paper, we carry out a statistical study and show that the polarization of transverse waves has a normal distribution, and the maximum corresponds to oscillations of the toroidal and poloidal components with the same amplitude. At the same time, the spatial distributions of toroidal and poloidal waves are clearly different, but only lead to a small shift in the position of the distribution maximum. This result suggests that in order to compare the theory with ULF wave observations it is necessary to take into account the processes of polarization change, which can affect wave-particle interactions in the magnetosphere.

Flux transfer events (FTEs) are magnetic structures generally believed to originate from time-varying magnetic reconnection at the Earth’s magnetopause. Despite years of research, the mechanism of how FTEs are formed through reconnection remains controversial. In various models, FTEs exhibit different global configurations. Studying the FTE axial orientation can provide insights into their global shape, thereby helping to distinguish the generation mechanisms. In this paper, taking advantage of the orbital characteristics of the four Cluster spacecraft, we devised a multi-spacecraft timing method to determine the axes of a total of 57 FTEs observed sequentially by Cluster during a high-latitude duskside magnetopause crossing. During the nearly five-hour observation, the interplanetary magnetic field (IMF) experienced a large rotation, leading to a substantial rotation of the magnetosheath magnetic field. The analysis results show two new features of the FTE axis that have not been reported before: (1) the axes of the FTEs gradually rotate in response to the turning of the IMF and the magnetosheath magnetic field; (2) the axes of the FTEs vary between the direction of the magnetosheath magnetic field and the direction of the reconnection X-line. These features indicate that FTEs may have a more complex global configuration than depicted by traditional FTE models.

Economic sustainability is one of the main factors restricting development of mercury pollution control technology in the flue gas. Renewable magnetospheres separated from fly ash can be used as adsorbent for mercury removal from coal-fired flue gas. Based on the actual working condition of the 1000 WM coal-fired unit, this paper analyzes the impact of magnetosphere and mercury recovery technology on the economic benefits of this technology. The results show that the recovery of magnetospheres and mercury can obtain higher economic returns. This not only can realize the deduction of operating costs, but also has certain economic investment potential. When the magnetic separation rate is greater than 6% and the selling price of the magnetosphere is greater than 720 CNY/t, the revenue of the magnetosphere recovery system can offset the operating cost of whole system. The internal rate of return of the system can reach 50% at most. When the selling price of mercury selenide is lower than 450 CNY/g, the single mercury recovery income is insufficient to offset the mercury removal cost. Within the selling price range of 450–500 CNY/g mercury selenide, the system can generate revenue, and the product qualification rate directly affects the profit and loss of the system. The coupling of magnetospheres and mercury recovery systems can make economic and technical parameters more moderate. When the selling price of magnetospheres is higher than 600 CNY/t, the magnetic separation rate is higher than 6%, and the selling price of mercury selenide is higher than 350 CNY/g, the internal return of the system will fluctuate within 13%∼120%, and the static investment recovery period will remain within 6 years. Overall, this study can provide economic guidance for mercury removal technology with renewable magnetospheres and provide data support for further commercialization of technology.

In 1961, Dungey suggested that magnetic reconnection occurs due to the solar-terrestrial interaction. The interplanetary magnetic field (IMF) is thought to merge with Earth’s geomagnetic field (GMF). After the reconnection process the newly formed magnetic flux tube, consisting of both the IMF and GMF, moves anti-sunward. Poleward-moving auroral forms (PMAFs) are believed to be the ionospheric signatures of this process, which transfers magnetic flux from the dayside to the nightside. This paper looks at the connection between the solar wind speed and the motion of the PMAF as it moves from the auroral oval, anti-sunward, into the polar cap. PMAFs are identified using both the meridian scanning photometer (MSP) and colored all-sky camera (ASC). Once the PMAFs are identified, the PMAF-SLOPE, vα (units of degrees per time) and the angle (αPMAF) the PMAF makes with the horizontal (Time axis), in the MSP plot are calculated. These values (vα and αPMAF) are individually plotted against the vx-component of the solar wind speed and the flow speed (total solar wind speed). The plots generate linear a relationship between PMAF-SLOPEs, vα, [or PMAF angles (αPMAF)], and the vx-component of the solar wind speed (or the flow speed). A total of 57 PMAF events from 8 different days were associated with solar wind speeds (vx-component) ranging from 344 to 679 km/s. The first linear plot, between the PMAF-SLOPE and solar wind speed (vx-component), shows a high correlation: rvα=0.944. A second linear plot, between αPMAF and the solar wind speed (vx-component) shows a very high correlation: rαPMAF=0.973. The conclusions obtained from this statistical study are: 1) both the PMAF-SLOPE vα and αPMAF are highly correlated to the vx-component of the solar wind, increasing when vx increases and vice versa, 2) PMAFs must be connected to both the IMF and GMF and are dragged anti-sunward, mostly by the vx-component of the solar wind, and 3) PMAFs are indeed the ionospheric footprints of a newly formed magnetic flux tube, due to dayside magnetic reconnection, being transferred from the dayside to nightside.

Abstract Optical remote sensing observations have suggested that the top layer of Europa's icy surface is heavily affected by external weathering agents. To model and understand these effects, it is necessary to characterize the environment as fully as possible. In this paper, we focus on one agent in the environment (energetic electrons). We show Juno electron data from its 2022 Europa flyby and other time periods. While the Juno sensor used here (Jupiter Energetic Particle Detector Instrument) was not designed to obtain high quality electron data in an intense radiation environment, it is possible to extract information such as how Europa blocks energetic particles from accessing some of the surrounding space. The decrease in charged particle flux in Europa's wake provides an upper limit on the precipitation fluxes of the same particles. We also report that electron pitch angle distributions near Europa for the single energy channel considered here are time variable and not isotropic.

When the solar wind encounters the blunt Earth's magnetosphere, a detached shock (i.e., the bow shock) forms at a distance about ten Earth radii from the Earth. The Earth's magnetosheath is a spatially-bounded transition region between the bow shock and the magnetopause, which directly interfaces with the magnetosphere. As the dynamic processes occurring in the magnetosheath may directly influence the magnetosphere, research on the magnetosheath has an important impact on our understanding of the magnetospheric dynamics and space weather. The magnetosheath is a natural laboratory of plasma dynamics, exhibiting various types of structures and waves. Studying these structures and waves can help us understand the magnetosheath's dynamic processes and nonlinear wave-particle interactions. Also, the magnetosheath provides an advantage condition for studying plasma turbulence. Turbulence within the magnetosheath features a distinctive characteristic than the solar wind turbulence, which provides another important in-situ turbulence laboratory except for the solar wind. Thanks to the high-resolution plasma measurements from the Cluster and Magnetospheric Multiscale (MMS) mission, some dynamic phenomena can be studied by in-situ observations in the magnetosheath. This paper reviews recent advances in studying the structure, waves and turbulence of the Earth's magnetosheath. Moreover, we primarily focus on domestic research using the Cluster and MMS missions data. The review is organized a brief introduction to the magnetosheath is provided. Then, the related researches on structures, waves and turbulence are described in three sections, respectively. At last, we also discuss some unsolved problems and the possible future research directions.

The present issue of Earth and Planetary Physics is dedicated to the near-space neutral and plasma environments of Mars. The issue includes nine papers that present new results on the properties of the Martian exosphere, ionosphere, and magnetosphere, from both observational and modeling points of view. Due to the similarity between the two objects, the issue also includes two additional papers on the near-Venus plasma environment.

In order to quantitatively investigate the mechanism of how magnetospheric convection is driven in the region of magnetotail lobes on a global scale, we analyzed data from the ARTEMIS spacecraft in the deep tail and data from the Cluster spacecraft in the near and mid-tail regions. Our previous work revealed that, in the lobes near the Moon’s orbit, the convection can be estimated by using ARTEMIS measurements of lunar ions’ velocity. Based on that, in this paper, we applied machine learning models to these measurements to determine which upstream solar wind parameters significantly drive the lobe convection in magnetotail regions, to help us understand the mechanism that controls the dynamics of the tail lobes. The results demonstrate that the correlations between the predicted and measured convection velocities for the machine learning models (>0.75) are superior to those of the multiple linear regression model (∼0.23–0.43) in the testing dataset. The systematic analysis shows that the IMF and magnetospheric activity play an important role in influencing plasma convection in the global magnetotail lobes.

In this paper, we study parameters of geomagnetic pulsations in the 1–4 mHz frequency range (Pc5/Pi3) in the magnetotail, utilizing data obtained by Cluster satellites at different levels of fluctuations in the interplanetary magnetic field (IMF) and the solar wind dynamic pressure in 2016. Particular attention is given to the conditions of “zero” disturbance when amplitudes of fluctuations in the interplanetary medium are smaller compared to their typical values. Both under quiet and disturbed conditions, waves of different spatial scales are recorded, with the occurrence rate of large-scale waves increasing under undisturbed conditions. Amplitudes of the large-scale waves occurring in the magnetotail under low intensity of fluctuations outside the magnetosphere are from few tenths to a few nanoteslas (nT), and their power is approximately equal in longitudinal and transverse components. Presumably, these waves are magnetotail eigen-modes.

In the paper, we present the result of an experimental study of north-south asymmetry of ultralow-frequency electromagnetic oscillations IPCL. This study is based on observations made at Mirny Observatory (Antarctica). IPCLs are excited in the dayside sector of the auroral oval in the range 3–10 min periods and represent one of the most powerful types of oscillations of Earth's magnetosphere. These oscillations were discovered in the 1970s during IPhE AS USSR polar expeditions organized by Prof. V.A. Troitskaya. We have shown that IPCL activity in Mirny depends on the inclination (north-south asymmetry) of interplanetary magnetic field (IMF) lines to the plane of the geomagnetic equator before the front of the magnetosphere. The result suggests a controlling exposure of IMF on the magnetospheric oscillations and gives rise to the hypothesis that IPCL are forced oscillations of a nonlinear dynamical system whose major structural elements are dayside polar cusps. The paper is dedicated to the memory of Professor V.A. Troitskaya (1917–2010).

In this paper, we investigate the electromagnetic electron cyclotron (EMEC) waves in the magnetosphere of Uranus. By using the method of characteristic solution, the expression for dispersion relation is drawn. Following kinetic approach, the growth rate and real frequency of EMEC waves is studied theoretically, considering the injection of cold plasma beam in the Uranian system. The observations made by a space probe launched by NASA, Voyager 2, showed unusual orientation of planet’s spin axis and presence of more particles in high energy tail in Uranian magnetospheric plasma. Therefore, in this paper Kappa distribution is employed instead of usual Maxwellian distribution. The study is extended to the parallel as well as the oblique propagation of EMEC waves with variation in temperature anisotropy, number density of electrons and angle of propagation with respect to magnetic field direction. It is found that these parameters support the growth rate of EMEC waves. But response of real frequency of these waves is not same as that of growth rate for all the cases. Numerical analysis also revealed that as the ratio of number density of cold to hot plasma increases growth rate of EMEC waves also increases. Thus, denser the beam is injected, more the growth can be observed. These results are appropriate for applications to space plasma environments and magnetospheric regimes for detailed comparative planetary study.

Analytical models for magnetospheric mass density, ρm, and average ion mass, M, were created from a database of ρm and electron density, ne, values from six spacecraft missions by making use of the Eureqa nonlinear genetic regression algorithm. All values of ρm were determined from Alfvén frequencies, and the values of ne were determined from plasma wave or spacecraft potential data. Models of varying complexity are listed. The most complex models appearing in this paper are capable of modeling ρm within a factor of 1.81, and M within a factor of 1.34 if ne is used as an input parameter, or within a factor of 1.45 if ne is not used. The most important parameters for modeling ρm are L, the solar EUV index F10.7, magnetic local time, MLT, the geomagnetic activity index Kp, and the solar wind dynamic pressure, Pdyn. The very simplest model for M depends on Kp. In more complex models for M including ne, the most important parameters are ne with L, F10.7, and Pdyn or Kp. In more complex models for M not including ne, the most important parameters are Kp, MLT, F10.7, L, and the auroral electrojet index, AE. Explanations for most of the dependencies are given. We also demonstrate the danger of calculating spatial dependence without taking account of different conditions sampled in different regions. Here we avoid that problem by using multivariant models.

MIO (Magnetosphere-Ionosphere Observatory) is designed to definitively fix a cause-and-effect problem: In the nightside magnetosphere-ionosphere system we don’t know what is connected to what. The MIO mission concept is to operate a powerful 1-MeV electron accelerator on a main spacecraft in the equatorial nightside magnetosphere: the electron beam is directed into the atmospheric loss cone to deposit ionizing electrons in the atmosphere sufficient to optically illuminate the magnetic footpoint of the spacecraft while 4 nearby daughter spacecraft make equatorial magnetospheric measurements. A network of ground-based optical imagers across Alaska and Canada will locate the optical beamspot thereby unambiguously establishing the magnetic connection between equatorial magnetospheric measurements and ionospheric phenomena. Critical gradient measurements will be made to discern magnetospheric field-aligned-current generator mechanisms. This enables the magnetospheric drivers of various aurora, ionospheric phenomena, and field-aligned currents to be determined. In support of the Solar and Space Physics (Heliophysics) 2022 Decadal Survey, an experienced team of engineers and scientists at The Johns Hopkins University Applied Physics Laboratory (APL) have developed a NASA HMCS (Heliospheric Mission Concept Study) mission concept that can achieve the science objectives. The mission concept presented here is the result of trade studies that optimized the mission with regard to factors such as science objectives, concept study requirements, space environment, engineering constraints, and risk. This Methods paper presents an overview of the MIO concept.

Abstract It has been suggested that ion foreshock waves originating in the solar wind upstream of the quasi-parallel (Q-||) shock can impact the planetary magnetosphere leading to standing shear Alfvén waves, i.e., the field line resonances (FLRs). In this paper, we carry out simulations of interaction between the solar wind and terrestrial magnetosphere under radial interplanetary magnetic field conditions by using a 3-D global hybrid model, and show the properties of self-consistently generated field line resonances through direct mode conversion in magnetospheric response to the foreshock disturbances for the first time. The simulation results show that the foreshock disturbances from the Q-|| shock can excite magnetospheric ultralow-frequency waves, among which the toroidal Alfvén waves are examined. It is found that the foreshock wave spectrum covers a wide frequency range and matches the band of FLR harmonics after excluding the Doppler shift effects. The fundamental harmonic of field line resonances dominates and has the strongest wave power, and the higher the harmonic order, the weaker the corresponding wave power. The nodes and anti-nodes of the odd and even harmonics in the equatorial plane are also presented. In addition, as the local Alfvén speed increases earthward, the corresponding frequency of each harmonic increases. The field-aligned current in the cusp region indicative of the possibly observable aurora is found to be a result of magnetopause perturbation which is caused by the foreshock disturbances, and a global view substantiating this scenario is given. Finally, it is found that when the solar wind Mach number decreases, the strength of both field line resonance and field-aligned current decreases accordingly.

Abstract On 12 May 2021 the interplanetary doppelgänger of the 9 May 2021 coronal mass ejection impacted the Earth's magnetosphere, giving rise to a strong geomagnetic storm. This paper discusses the evolution of the various events linking the solar activity to the Earth's ionosphere with special focus on the effects observed in the circumterrestrial environment. We investigate the propagation of the interplanetary coronal mass ejection and its interaction with the magnetosphere—ionosphere system in terms of both magnetospheric current systems and particle redistribution, by jointly analyzing data from interplanetary, magnetospheric, and low Earth orbiting satellites. The principal magnetospheric current system activated during the different phases of the geomagnetic storm was correctly identified through the direct comparison between geosynchronous orbit observations and model predictions. From the particle point of view, we have found that the primary impact of the storm development is a net and rapid loss of relativistic electrons from the entire outer radiation belt. Our analysis shows no evidence for any short‐term recovery to pre‐storm levels during the days following the main phase. Storm effects also included a small Forbush decrease driven by the interplay between the interplanetary shock and subsequent magnetic cloud arrival.

This paper deals with extreme conditions of the global magnetosphere disturbance: very quiet and greatly disturbed, and their relationship with interplanetary medium parameters. The degree of global magnetosphere disturbance was estimated from the monthly and annual number of magnetically quiet and magnetically disturbed days. The cyclic and seasonal distributions of magnetically quiet and disturbed days were compared, and their relationship with interplanetary medium parameters in solar cycles 20–24 was analyzed. Magnetically quiet days are shown to be mainly observed at the ascending phase of solar activity and during the winter solstice season. Magnetically disturbed days dominate at the descending phase of the solar cycle and during the equinox season. An anomalously large increase in the number of quiet days was found in solar cycle 24 as compared to previous cycles. It has been established that the cyclic variation in the annual number of quiet and disturbed days is determined by the behavior and magnitude of the speed, temperature, dynamic pressure of solar wind plasma and the interplanetary magnetic field modulus. The detected burst in the number of quiet days during the ascending phase of solar cycle 24 is assumed to reflect internal processes on the Sun and related changes in interplanetary medium parameters. The patterns of cyclical and seasonal variation in the number of magnetically quiet and disturbed days and their relationship with the solar wind parameters can be used to predict space weather.

It has been found in experiments at the SURA mid-latitude heating facility that the modification of the ionospheric F2 layer by powerful HF radio waves gives rise to artificial injection of energetic electrons from the Earth’s radiation belt into the atmosphere. The spectral, energy, and spatial characteristics of such an injection are presented in the paper. It is significant that the energetic electrons excite the atoms and molecules of the atmosphere to Rydberg energy levels, followed by the transition of the excited atoms and molecules to lower energy states, accompanied by the radiation of the microwave electromagnetic emissions. It has been shown that the artificial injection of energetic electrons can be considered as an independent powerful source of generation of secondary artificial turbulence, the effect of which manifests itself at ionospheric and mesospheric heights both near the heating facility and at a large distance from it up to a thousand or more kilometers. Examples of such generation are given.

Abstract Solar wind‐magnetosphere coupling functions have now been in use for almost 50 years. In that time, a very large number of formulations have been proposed. As they become increasingly subsumed into systems analysis and machine‐learning studies of the magnetosphere, it is timely to establish best practice in their derivation and study their limitations. This paper reports on a number of studies carried out to establish some key points. Particular attention is paid to the best metric used to evaluate their performance and how it depends on the application for which the coupling function is intended.

In this paper, we analyze one reconnection event observed by the Magnetospheric Multiscale (MMS) mission at the earth’s magnetopause. In this event, the spacecraft crossed the reconnection current sheet from the magnetospheric side to the magnetosheath side, and whistler waves were observed on both the magnetospheric and magnetosheath sides. On the magnetospheric side, the whistler waves propagated quasi-parallel to the magnetic field and toward the X-line, while on the magnetosheath side they propagated almost anti-parallel to the magnetic field and away from the X-line. Associated with the enhancement of the whistler waves, we find that the fluxes of energetic electrons are concentrated around the pitch angle 90° when their energies are higher than the minimum energy that is necessary for the resonant interactions between the energetic electrons and whistler waves. This observation provides in situ observational evidence of resonant interactions between energetic electrons and whistler waves in the magnetic reconnection.

Abstract The Super Dual Auroral Radar Network (SuperDARN) is a network of high-frequency (HF) radars located in the high- and mid-latitude regions of both hemispheres that is operated under international cooperation. The network was originally designed for monitoring the dynamics of the ionosphere and upper atmosphere in the high-latitude regions. However, over the last approximately 15 years, SuperDARN has expanded into the mid-latitude regions. With radar coverage that now extends continuously from auroral to sub-auroral and mid-latitudes, a wide variety of new scientific findings have been obtained. In this paper, the background of mid-latitude SuperDARN is presented at first. Then, the accomplishments made with mid-latitude SuperDARN radars are reviewed in five specified scientific and technical areas: convection, ionospheric irregularities, HF propagation analysis, ion-neutral interactions, and magnetohydrodynamic (MHD) waves. Finally, the present status of mid-latitude SuperDARN is updated and directions for future research are discussed.

This paper deals with Pc5 magnetospheric pulsations featuring positive azimuthal wave numbers registered with the mid-latitude coherent decameter radar located near Ekaterinburg (EKB). The azimuthal wave numbers are determined using adjacent high time resolution beams directed toward the magnetic pole. Approximately 13 % of all steady waves registered with the radar propagate eastward. We have examined ten cases of wave observations with both small and high positive wave numbers, which occurred between April 2014 and March 2015. We performed a wavelet analysis of the data sets, estimated wavelength in radial direction for four cases, and determined meridional phase propagation direction. In three cases, the results are consistent with field line resonance behavior. However, in the majority of the studied events wave frequencies are considerably lower than those of field line resonance, which were derived from satellite data on magnetic field and particle density. These waves may be classed with the drift-compressional mode.

The technique to estimate the mass density in the magnetosphere using the physical properties of observed magnetohydrodynamic waves is known as magnetoseismology. This technique is important in magnetospheric research given the difficulty of determining the density using particle experiments. This paper presents a review of magnetoseismic studies based on satellite observations of standing Alfvén waves. The data sources for the studies include AMPTE/CCE, CRRES, GOES, Geotail, THEMIS, Van Allen Probes, and Arase. We describe data analysis and density modeling techniques, major results, and remaining issues in magnetoseismic research.

Abstract The radiation belts of the Earth, filled with energetic electrons, comprise complex and dynamic systems that pose a significant threat to satellite operation. While various models of electron flux both for low and relativistic energies have been developed, the behavior of medium energy (120–600 keV) electrons, especially in the MEO region, remains poorly quantified. At these energies, electrons are driven by both convective and diffusive transport, and their prediction usually requires sophisticated 4D modeling codes. In this paper, we present an alternative approach using the Light Gradient Boosting (LightGBM) machine learning algorithm. The Medium Energy electRon fLux In Earth's outer radiatioN belt (MERLIN) model takes as input the satellite position, a combination of geomagnetic indices and solar wind parameters including the time history of velocity, and does not use persistence. MERLIN is trained on >15 years of the GPS electron flux data and tested on more than 1.5 years of measurements. Tenfold cross validation yields that the model predicts the MEO radiation environment well, both in terms of dynamics and amplitudes o f flux. Evaluation on the test set shows high correlation between the predicted and observed electron flux (0.8) and low values of absolute error. The MERLIN model can have wide space weather applications, providing information for the scientific community in the form of radiation belts reconstructions, as well as industry for satellite mission design, nowcast of the MEO environment, and surface charging analysis.

In this paper, the Space Weather Modeling Framework (SWMF) is used to simulate the real-time response of the magnetosphere to a solar wind event on June 5, 1998, in which the interplanetary magnetic field shifted its direction from north to south. Since most current models do not take into account convective effects of the inner magnetosphere, we first study the importance of Rice Convection Model (RCM) in the global model. We then focus on the following four aspects of the magnetosphere’s response: the magnetosphere’s density distribution, the structure of its magnetic field lines, the area of the polar cap boundary, and the corresponding ionospheric current change. We find that (1) when the IMF changes from north to south in this event, high magnetosheath density is observed to flow downstream along the magnetopause with the solar wind; low-latitude reconnection at dayside occurs under the southward IMF, while the magnetic field lines in the tail lobe caudal, caused by the nightside high latitude reconnection, extend into the interplanetary space. Open magnetic field lines exist simultaneously at both high and low latitudes at the magnetopause; (2) the area of the polar cap is obviously increased if the IMF turns from the north to the south; this observation is highly consistent with empirical observations; (3) the ionospheric field align current in the northern hemisphere is stronger than in the southern hemisphere and also increases as the IMF changes from north to south. SWMF with the Rice Convection effect provides reliable modeling of the magnetospheric and ionospheric response to this solar wind variation.

The aim of this paper is to structure and extend the knowledge of solar chromospheric sources of oscillations in the solar wind and their relationships with pulsations registered in the magnetosphere. We compare the oscillation spectra that we observe using instruments of the Institute of Solar-Terrestrial Physics in different chromospheric structures with those observed in the solar wind and magnetosphere. We explore the possibility that the observed periodic variations of the chromospheric line widths can be interpreted as torsional Alfvén wave manifestation—this mode can propagate long distances without dissipating in the interplanetary space; it can penetrate into Earth’s magnetosphere directly or due to processes occurring at the plasmapause. We emphasize the similarities in the oscillation characteristics observed in different media, the similarities in the parameters of the media themselves and the processes developing in them. We believe that similar approaches can be applied to studying these media.

The paper discusses the outer electron belt dynamics, adiabatic and nonadiabatic mechanisms of increases and losses of energetic electrons. Under undisturbed conditions, the outer electron belt gradually empties: in the inner magnetosphere due to electron losses in the atmosphere and in the quasi-trapping region due to losses at the magnetopause because drift shells of electrons are not closed there. The latter process does not occur in normal years due to the masking replenishment by freshly accelerated particles, but in years of extremely low activity it leads to a significant decrease in the electron population of the belt. During the magnetic storm main phase, the first reason for the decrease in the electron flux intensity is the adiabatic cooling associated with conservation of adiabatic invariants and complemented by injection of electrons into the atmosphere and their losses at the magnetopause. Electron flux increases involve EB electron injection by the induction electric field of substorm activation and by the large-scale solar wind electric field, with pitch energy diffusion along with adiabatic heating in the recovery phase. The rate of electron flux recovery after a storm is determined by the ratio of nonadiabatic increases and losses; hence the electron flux represents a continuous series from low to very high values. The combination of these processes determines the individual character of radiation belt development during each magnetic storm and the behavior of the belt in the quiet time.

Precursor emissions are found in some short gamma-ray bursts (SGRBs). In this paper, we review the theories and observations of the SGRB precursor and discuss its prospect as an electromagnetic counterpart of the gravitational wave event produced by neutron star (NS) mergers. The observed luminosity, spectrum, and duration of precursors are explained by the magnetospheric interaction model during the inspiral or the cocoon/jet shock breakout model during the jet propagation. In general, these two models predict that the precursor will be weaker than the main GRB, but will be of a larger opening angle, which makes it an advantageous gamma-ray counterpart for NS mergers in the local Universe, especially for NS - black hole mergers with very low mass ratios, in which the main GRBs are not expected. The joint observation of the precursor, SGRB, and gravitational wave will help to reveal the jet launch mechanism and post-merger remnant.

It has been one hundred years since the birth of the outstanding scientist Professor V.A. Troitskaya. Her remarkable achievements in solar-terrestrial physics are widely known. For many years, Valeria A. Troitskaya was the President of the International Association of Geomagnetism and Aeronomy. This article deals with only one aspect of the multifaceted creative activity of V.A. Troitskaya. It relates to the problem of sources of ultra-low frequency (ULF) electromagnetic oscillations and waves outside Earth’s magnetosphere. We were fortunate to work under the leadership of V.A. Troitskaya on this problem. In this paper, we briefly describe the history from the emergence of the idea of the extramagnetospheric origin of dayside permanent ULF oscillations in the late 1960s to the modern quest made by ground and satellite means for ULF waves excited by solar surface oscillations propagating in the interplanetary medium and reaching Earth.

Abstract In this paper, we present a statistical and case analysis of nighttime Pc3 pulsations observed from middle to equatorial latitudes during the year 2003. We found two groups of nighttime Pc3 pulsations. Pc3s of the first group are in fact the nightside counterpart of morning Pc3 pulsations with large azimuthal scales slowly attenuating toward midnight. Such night signatures of morning Pc3 waves are observed during the periods of fast solar wind ( $$V>500\,\hbox {km/s}$$ V > 500 km/s ). The second type is the locally generated night Pc3 pulsations. They can be observed under moderate solar wind velocities. Maximal occurrence rates and amplitudes for these pulsations are recorded at middle geomagnetic latitudes near the local magnetic midnight. Probably, they are associated with auroral activations or local non-substorm bursty processes. Graphical abstract An example of a nighttime Pc3 pulsation Graphical abstract Empirical probability density function of the solar wind speed for the intervals with the two types of night Pc3 pulsations and for all the intervals analyzed.

The paper reviews studies of the dynamics of relativistic electrons in the geosynchronous region. It lists the physical processes that lead to the acceleration of electrons filling the outer radiation belt. As one of the space weather factors, high-energy electron fluxes pose a serious threat to the operation of satellite equipment in one of the most populated orbital regions. Necessity is emphasized for efforts to develop methods for forecasting the situation in this part of the magnetosphere, possible predictors are listed, and their classification is given. An example of a predictive model for forecasting relativistic electron flux with a 1–2-day lead time is proposed. Some questions of practical organization of prediction are discussed; the main objectives of short-term, medium-term, and long-term forecasts are listed.

In this paper whistler mode waves have been investigated in magnetosphere of Saturn. The derivation for perturbed distribution function, dispersion relation and growth rate have been determined by using the method of characteristic and kinetic approach. Analytical expressions for growth rate and real frequency of whistlers propagating oblique to magnetic field direction are attained. Calculations have been performed at 6 radial distances in plasma sheet region of Saturn’s magnetosphere as per data provided by Cassini. Work has been extended for bi-Maxwellian as well as Loss-cone distribution function. Parametric analysis show that temperature anisotropy, increase in number density, energy density and angle of propagation increases the growth rate of whistler waves along with significant shift in wave number. In case of Loss-cone distribution, increase in growth rate of whistlers is significantly more than for bi-Maxwellian distribution function. Generation of second harmonics can also be seen in the graphs plotted. It is concluded that parallel DC field stabilizes the wave and temperature anisotropy, angle of propagation, number density and energy density of electrons enhances the growth rate. Thus the results are of importance in analyzing observed VLF emissions over wide spectrum of frequency range in Saturnian magnetosphere. The analytical model developed can also be used to study various types of instabilities in planetary magnetospheres.

Renewed interest in active experiments with relativistic particle beams in space has led to the development of solid-state radio-frequency (RF) linear accelerators (linac) that can deliver MeV electron beams but operate with low-voltage DC power supplies. The solid-state RF amplifiers used to drive the accelerator are known as high-electron mobility transistors (HEMTs), and at C-band (5–6 GHz) are capable of generating up to 500 watts of RF power at 10% duty factor in a small package, i.e., the size of a postage stamp. In operation, the HEMTs are powered with 50 V DC as their bias voltage; they thus can tap into the spacecraft batteries or electrical bus as the primary power source. In this paper we describe the initial testing of a compact space-borne RF accelerator consisting of individual C-band cavities, each independently powered by a gallium nitride (GaN) HEMT. We show preliminary test results that demonstrate the beam acceleration in a single C-band cavity powered by a single HEMT operating at 10% duty factor. An example of active beam experiments in space that could benefit from the HEMT-powered accelerators is the proposed Magnetosphere-Ionosphere Connection (CONNEX) experiment (Dors et al., 2017).

Magnetic fields in the inner magnetosphere can be obtained as vector sums of the Earth’s own internal magnetic field and magnetic fields stemming from currents flowing in the space plasma. While the Earth’s internal magnetic field is accurately described by the International Geomagnetic Reference Field (IGRF) model, the characterization of the external magnetic fields is significantly more complicated, as they are highly variable and dependent on the actual level of the geomagnetic activity. Tsyganenko family magnetic field models (T89, T96, T01, TA15B, TA15N), parameterized by the geomagnetic activity level and solar wind parameters, are often used by the involved community to describe these fields. In the present paper, we use a large dataset (2001–2018) of magnetospheric magnetic field measurements obtained by the four Cluster spacecraft to assess the accuracy of these models. We show that, while the newer models (T01, TA15B, TA15N) perform significantly better than the old ones (T89, T96), there remain some systematic deviations, in particular at larger latitudes. Moreover, we compare the locations of the min-B equator determined using the four-point Cluster spacecraft measurements with the locations determined using the magnetic field models. We demonstrate that, despite the newer models being comparatively slightly more accurate, an uncertainty of about one degree in the latitude of the min-B equator remains.

This paper explores the spatial variations of the statistical scaling features of low to high latitude geomagnetic field fluctuations at Swarm altitude. The data for this study comes from the vector field magnetometer onboard Swarm A satellite, measured at low resolution (1 Hz) for one year (from 9 March 2016, to 9 March 2017). We estimated the structure-function scaling exponents using the p-leaders discrete wavelet multifractal technique, from which we obtained the singularity spectrum related to the magnetic fluctuations in the North-East-Center (NEC) coordinate system. From this estimation, we retain just the maximal fractal subset, associated with the Hurst exponent H. Here we present thresholding for two levels of the Auroral Electrojet index and almost the whole northern and southern hemispheres, the Hurst exponent, the structure-function scaling exponent of order 2, and the multifractal p-exponent width for the geomagnetic fluctuations. The latter quantifies the relevance of the multifractal property. Sometimes, we found negative values of H, suggesting a behavior similar to wave breaking or shocklet-like propagating front. Furthermore, we found some asymmetries in the magnetic field turbulence between the northern and southern hemispheres. These estimations suggest that different turbulent regimes of the geomagnetic field fluctuations exist along the Swarm path.

Internet-based system of Space Monitoring Data Center (SMDC) of Skobeltsyn Institute of Nuclear Physics of Moscow State University (SINP MSU) has been developed to predict and analyze radiation conditions in near-Earth space. This system contains satellite measurement databases and operational models and devoted to collect, store and process space weather monitoring data in the near real-time. SMDC operational services acquire data from ACE, SDO, GOES, Electro-L, Meteor-M satellites and use them for forecasting, now-casting and post-casting of space weather factors. This paper is intended to give overview of operational services of SMDC Internet-based system and demonstrate their possibilities and limitations to analyze space weather phenomena and predict radiation and geomagnetic conditions in the near-Earth space during February 14–March 5, 2014. This prolonged period of high level solar and geomagnetic activity demonstrates various manifestations of the space weather: solar proton events, geomagnetic storms and outer radiation belt (RB) dynamics. Solar sources of interplanetary space disturbances and their influence on geomagnetic and radiation state of the Earth’s magnetosphere were described using output coming from SMDC’ Web-based applications. Validation of SMDC’s operational models was performed based on the quality of description of the physical conditions in near-Earth space during space weather events observed from February 14 to March 5, 2014. The advantages and disadvantages of SMDC operational services are illustrated and discussed based on comparison with data obtained from satellites.

Using the reconstruction of power input to the magnetosphere presented in Paper 1 Lockwood et al. [J Space Weather Space Clim 7 (2017a)], we reconstruct annual means of the geomagnetic Ap and AE indices over the past 400 years to within a 1-sigma error of ±20%. In addition, we study the behaviour of the lognormal distribution of daily and hourly values about these annual means and show that we can also reconstruct the fraction of geomagnetically-active (storm-like) days and (substorm-like) hours in each year to accuracies of to accuracies of ~50%, including the large percentage uncertainties in near-zero values. The results are the first physics-based quantification of the space weather conditions in both the Dalton and Maunder minima. Looking to the future, the weakening of Earth's magnetic moment means that the terrestrial disturbance levels during a future repeats of the solar Dalton and Maunder minima will be weaker and we here quantify this effect for the first time.

Neutron stars are compact objects rotating at high speed, up to a substantial fraction of the speed of light (up to 20% for millisecond pulsars) and possessing ultra-strong electromagnetic fields (close to and sometimes above the quantum critical field of 4.4 × 10 9 T ). Moreover, due to copious e ± pair creation within the magnetosphere, the relativistic plasma surrounding the star is forced into corotation up to the light cylinder where the corotation speed reaches the speed of light. The neutron star electromagnetic activity is powered by its rotation which becomes relativistic in the neighborhood of this light cylinder. These objects naturally induce relativistic rotation on macroscopic scales about several thousands of kilometers, a crucial ingredient to trigger the central engine as observed on Earth. In this paper, we elucidate some of the salient features of this corotating plasma subject to efficient particle acceleration and radiation, emphasizing several problems and limitations concerning current theories of neutron star magnetospheres. Relativistic rotation in these systems is indirectly probed by the radiation produced within the magnetosphere. Depending on the underlying assumptions about particle motion and radiation mechanisms, different signatures on their light curves, spectra, pulse profiles and polarization angles are expected in their broadband electromagnetic emission. We show that these measurements put stringent constraints on the way to describe particle electrodynamics in a rotating neutron star magnetosphere.

Using information on geomagnetic activity, sunspot numbers and cosmogenic isotopes, supported by historic eclipse images and in conjunction with models, it has been possible to reconstruct annual means of solar wind speed and number density and heliospheric magnetic field (HMF) intensity since 1611, when telescopic observations of sunspots began. These models are developed and tuned using data recorded by near-Earth interplanetary spacecraft and by solar magnetograms over the past 53 years. In this paper, we use these reconstructions to quantify power input into the magnetosphere over the past 400 years. For each year, both the annual mean power input is computed and its distribution in daily means. This is possible because the distribution of daily values divided by the annual mean is shown to maintain the same lognormal form with a constant variance. This study is another important step towards the development of a physics-based, long-term climatology of space weather conditions.