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This document is a summary of a special issue of the journal Earth, Planets & Space titled "VLF/ELF remote sensing of ionospheres and magnetospheres." The issue is a result of the 9th VLF/ELF Remote Sensing of Ionospheres and Magnetospheres (VERSIM) Workshop, which took place virtually in November 2020. The workshop focused on studying the behavior of the magnetosphere and ionosphere using Extremely Low Frequency (ELF) and Very Low Frequency (VLF) radio waves. The special issue includes 13 papers on various topics related to VLF/ELF remote sensing, including spacecraft observations, particle simulations, and technical issues. The authors express their gratitude to the reviewers of the articles and declare no competing interests. The guest editors for the special issue are Yoshiharu Omura, Jacob Bortnik, Mark Clilverd, Andrei Demekhov, and Yohei Miyake. [Extracted from the article]

Here, we extend the scope of the Gamayunov and Engebretson (2021, hereinafter Paper 1), https://doi.org/10.1029/2021JA029247 work by analyzing the low frequency ultra‐low‐frequency (ULF) wave power spectra in the Earth's inner magnetosphere during high speed stream (HSS) and quiet solar wind (QSW) driving conditions in the upstream solar wind (SW) and comparing our results to the results of Paper 1, where the statistics of ULF wave power spectra during coronal mass ejections (CMEs) are presented. The most important results of our statistical and comparative analyses are as follows. (a) During CMEs, HSSs, and QSW, the magnetic field power spectra of the transverse and compressional fluctuations are well approximated by power laws in the ∼mHz–Hz frequency range, where on average the parameters of power law fits during CMEs and HSSs are close, and those during QSW differ considerably from the respective parameters during CMEs and HSSs. (b) The dominance of the average compressional power over the average transverse power for the low frequency ULF waves during the 0 < SYM/H ≲ 25 nT geomagnetic conditions may serve as a proxy of HSSs in the upstream SW, whereas the opposite relation between the average powers is an indication of CMEs. (c) Independently of the SW driving conditions, a turbulent energy cascade from low frequencies in the ULF wave frequency range into the higher frequency range exists in the Earth's inner magnetosphere, supplying the nonthermal electromagnetic seed fluctuations needed for the growth of electromagnetic ion cyclotron waves (∼Hz) due to relaxation of unstable distributions of energetic magnetospheric ions. Key Points: Statistics of low frequency ultra‐low‐frequency wave power spectra during high speed streams and quiet solar wind are presented and compared to the statistics of the coronal mass ejection driven eventsA turbulent energy cascade in the Earth's inner magnetosphere exists independently of the solar wind driving conditionsA turbulent energy cascade supplies seed fluctuations needed for electromagnetic ion cyclotron wave growth due to instabilities of the energetic magnetospheric ions [ABSTRACT FROM AUTHOR]

This paper presents the description of antenna parameters related to its radiation/reception capabilities influenced by the plasma parameters in the environment surrounding the antenna, complementing the existing works on the antenna parameters (e.g., the impedance or currents). The parameters considered are the radiation zones' radiuses (inductive, Fresnel, Fraunhofer), scalloping and directivity; a method of transformation of the air/vacuum-measured radiation/reception pattern to the pattern expected for given plasmatic conditions is also considered. Three different simplified plasma conditions are taken into account (different electron densities: 1.4 × 1012 m−3, 4 × 1011 m−3 and 108 m−3), with varying antenna length (1 m, 10 m, 100 m) and signal propagation mode (classic-ionospheric, whistler and Alfvén). The findings show that the presented antenna parameters and its radiation/reception pattern are heavily dependent on the plasma conditions. These findings can be used to form additional requirements and constraints for the mechanical design of new instrumentation for space weather measurements on board spacecraft (e.g., moving the antennas away from the spacecraft in order not to alter their radiation/reception patterns or not to measure the plasma around the spacecraft) or more accurate data processing from existing space weather satellites, allowing, for example, a more precise triangulation of the signal source or its spectral power regarding the actual performance of the antennas submerged in plasma. [ABSTRACT FROM AUTHOR]

On 7 January 2014, a solar storm erupted, which eventually compressed the Earth's magnetosphere leading to the generation of chorus waves. These waves enhanced local wave‐particle interactions and led to the precipitation of electrons from 10 s eV to 100 s keV. This paper shows observations of a low energy cutoff in the precipitation spectrum from Van Allen Probe B Helium Oxygen Proton Electron measurements. This low energy cutoff is well replicated by the predicted loss calculated from pitch angle diffusion coefficients from wave and plasma observations on Probe B. To our knowledge, this is the first time a single spacecraft has been used to demonstrate an accurate theoretical prediction for chorus wave‐induced precipitation and its low energy cutoff. The specific properties of the precipitating soft electron spectrum have implications for ionospheric activity, with the lowest energies mainly contributing to thermospheric and ionospheric upwelling, which influences satellite drag and ionospheric outflow. Plain Language Summary: On 7 January 2014, a large storm erupted from the Sun. This storm encountered the Earth and compressed the magnetosphere a few days later. The compression of the magnetosphere led to the creation of chorus waves, a wave‐type known to interact only with electrons with specific energies. In this case, the waves interacted with electrons in the magnetosphere's outer radiation belt. They caused the loss of electrons from 10 s eV to 100 s keV into the ionosphere and upper atmosphere. This paper uses theory to determine which energies we expect will interact with the observed chorus wave. We use the Helium Oxygen Proton Electron instrument from the Van Allen Probes to see if our predictions are correct. We care about these processes because the loss of these electrons can affect ionospheric activity. Key Points: Upper band chorus waves can have a minimum resonant energy in the 10 s eV energy rangeChanges in the minimum resonant energy can change the cut off for what lower energy particles will be lostThe lower energy cut off can be observed in the Van Allen Probes Helium Oxygen Proton Electron data [ABSTRACT FROM AUTHOR]

The Earth's magnetosphere is a region occupied by many artificial satellites, and also is a region that spacecraft must cruise during the deep-space exploration. In this sense, the Earth's magnetosphere is closely related to human activity and is a candidate for us to expand our living space. Generally, the Earth's magnetosphere can preclude most energetic particles from the Sun and the interstellar space, effectively protecting human beings on the Earth from being attacked and thus making the Earth to be a habitable planet. However, in some conditions, the Earth's magnetosphere becomes dynamic and energetic, and consequently may damage the artificial satellites, threaten the astronauts' health, and disrupt the ground infrastructure, which leads to a decline in the national economy. Therefore, investigating how energy is injected into the magnetosphere, how it is transported in the magnetosphere, and how it is ultimately dissipated in the magnetosphere are the key issues in space physics. Targeting these key issues, in this paper, we review the recent progress on them. Particularly, we introduce the relevant scientific questions, models, methods, and spacecraft missions, for better building a physical link among the energy injection, transport, and dissipation in the magnetosphere, present an energy chain of the magnetosphere, reveal the relationship between such energy chain and the space weather events, and discuss the forecasting and warning methods for energetic-particle events in the magnetosphere. The magnetospheric energy chain discussed in this paper will help us reveal the mechanisms of space weather events, establish the models of space environment, and forecast the disastrous space weather events. [ABSTRACT FROM AUTHOR]

Auroral precipitation is the second major energy source after solar irradiation that ionizes the Earth's upper atmosphere. Diffuse electron aurora caused by wave-particle interaction in the inner magnetosphere (L < 8) takes over 60% of total auroral energy flux, strongly contributing to the ionospheric conductance and thus to the ionosphere-thermosphere dynamics. This paper quantifies the impact of chorus waves on the diffuse aurora and the ionospheric conductance during quiet, medium, and strong geomagnetic activities, parameterized by AE <100, 100 < AE < 300, and AE > 300, respectively. Using chorus wave statistics and inner-magnetosphere plasma conditions from Timed History Events and Macroscale Interactions during Substorms (THEMIS) observations, we directly derive the energy spectrum of diffuse electron precipitation under quasi-linear theory. We then calculate the height-integrated conductance from the wave-driven aurora spectrum using the electron impact ionization model of Fang et al. (Geophys. Res. Lett., 2010, 37) and the MSIS atmosphere model. By utilizing Fang's ionization model, the US Naval Research Laboratory Mass Spectrometer and Incoherent Scattar Radar (NRLMSISE-00) model from 2000s for the neutral atmosphere components, and the University of California, Los Angeles (UCLA) Full Diffusion Code, we improve upon the standard generalization of Maxwellian diffuse electron precipitation patterns and their resulting ionosphere conductance. Our study of global auroral precipitation and ionospheric conductance from chorus wave statistics is the first statistical model of its kind. We show that the total electron flux and conductance pattern from our results agree with those of Ovation Prime model over the pre-midnight to post-dawn sector as geomagnetic activity increases. Our study examines the relative contributions of upper band chorus (UBC) and lower band chorus wave (LBC) driven conductance in the ionosphere. We found LBC waves drove diffuse electron precipitation significantly more than UBC waves, however it is possible that THEMIS data may have underestimated the upper chorus band wave observations for magnetic latitudes below 65 °. [ABSTRACT FROM AUTHOR]

Magnetohydrodynamic (MHD) numerical simulation has emerged as a pivotal tool in space physics research, witnessing significant advancements. This methodology offers invaluable insights into diverse space physical phenomena based on solving the fundamental MHD equations. Various numerical methods are utilized to approximate the MHD equations. Among these, the space–time conservation element and solution element (CESE) method stands out as an effective computational approach. Unlike traditional numerical schemes, the CESE method significantly enhances accuracy, even at the same base point. The concurrent discretization of space and time for conserved variables inherently achieves higher-order accuracy in both dimensions, without the need for intricate higher-order time discretization processes, which are often challenging in other methods. Additionally, this scheme can be readily extended to multidimensional cases, without relying on operator splitting or direction alternation. This paper primarily delves into the remarkable progress of CESE MHD models and their applications in studying solar wind, solar eruption activities, and the Earth's magnetosphere. We aim to illuminate potential avenues for future solar–interplanetary CESE MHD models and their applications. Furthermore, we hope that the discussions presented in this review will spark new research endeavors in this dynamic field. [ABSTRACT FROM AUTHOR]

The Earth's magnetosheath and cusps are the sources of soft X‐rays. In the accompanying paper (Part 1) and this paper, we discuss the methods of finding the magnetopause position by analyzing the X‐ray images. We use the software developed for the Soft X‐ray Imager (SXI) on board the forthcoming Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission. We show how to find the maximum SXI count rate in noisy count maps. We verify the assumption that the maximum of the X‐ray emissivity integrated along the Line‐of‐Sight (Ix) is tangent to the magnetopause. We consider two cases using two MHD models and apply different methods of magnetospheric masking. Overall, the magnetopause is located close to the maximum Ix gradient or between the maximum Ix gradient and the maximum Ix depending on the method used. But since the angular distance between the maximum Ix gradient and the maximum Ix is relatively small (about 3°), the maximum Ix might be used as an indicator of the outer boundary of a wide magnetopause layer usually obtained in MHD simulations. Plain Language Summary: This is the second of two papers presenting the techniques to estimate the Earth's magnetopause location (the outer boundary of the magnetosphere) under the impact of the highly dynamic solar wind. Our knowledge of the overall shape of the magnetopause will be vastly improved when we start using X‐ray imagers to monitor large areas around this boundary as the solar wind varies. In this second paper of the series, we make use of the X‐ray emissions in the vicinity of the Earth simulated in the first paper for two case studies with vastly different incoming solar wind conditions. Here we examine different methods of how to extract the magnetopause shape and position from X‐ray maps of the type that will be returned by the X‐ray imager due to flying on the SMILE mission. Key Points: Different methods of finding the location and shape of the magnetopause from X‐ray images give consistent resultsMaximum integrated emissivity indicates the outer boundary of the magnetopauseThis work is made in preparation for the forthcoming Solar wind Magnetosphere Ionosphere Link Explorer mission [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]

In the nightside region of Earth's magnetosphere, braking oscillations or buoyancy modes have been associated with the occurrence of low entropy bubbles. These bubbles form in the plasma sheet, particularly during geomagnetically disturbed times, and because of interchange, move rapidly earthward and may eventually come to rest in the inner plasma sheet or inner magnetosphere. Upon arrival, they often exhibit damped oscillations with periods of a few minutes and are associated with Pi2 pulsations. Previously we used the thin filament approximation to compare the frequencies and modes of buoyancy waves using magnetohydrodynamic (MHD) ballooning and classic interchange theory. Interchange oscillations differ from the more general MHD oscillations by assuming constant pressure along a magnetic field line. It was determined that MHD ballooning and interchange modes are similar for plasma sheet field lines but differ for field lines that map to the inner magnetosphere. This suggested that the classic interchange formulation was only valid in the plasma sheet. This paper tests the hypothesis that the agreement between MHD ballooning and classic interchange could be restored inside a bubble. We create a small region of entropy depletion in the magnetotail and compare the buoyancy mode properties. At some locations inside the bubble, the MHD ballooning buoyancy modes resemble interchange modes but with lower frequencies than those of the unperturbed background. Unstable modes are found on the earthward edge of the bubble, while at the tailward edge, MHD ballooning predicts a slow mode wave solution not seen in the pure interchange solution. Plain Language Summary: Low entropy plasma bubbles often form in the nightside region of the Earth's magnetosphere which move rapidly earthward and come to rest near the Earth. These bubbles often exhibit damped buoyancy oscillations with periods of a few minutes. Buoyancy waves are analogous to neutral‐atmospheric gravity waves, in which the buoyant force is gravity rather than magnetic tension. This work seeks to better understand the properties of these oscillations. We use a thin filament approximation that assumes that magnetic field lines can be approximated by thin magnetic filaments that can slip through the background. We use two approaches: MHD ballooning theory and classic interchange theory to examine the properties the oscillations in a small entropy‐depleted plasma bubble in the magnetotail. In the bubble, we find that in some regions the interchange and ballooning modes overlap, resulting in frequencies that are much lower than the background. On the Earthward edge of the bubble, we find regions of instability, while on the tailward edge within the bubble, MHD predict a slow mode wave in contrast with the interchange treatment. Key Points: This paper investigates buoyancy modes within a low entropy bubble in the Earth's nightside region using a thin filament approximationIn previous work, we reported that MHD ballooning modes resemble interchange modes in the plasmasheet but not in the inner magnetosphereFor a low entropy bubble near the Earth, we find that MHD ballooning results are closer to interchange modes [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Although initially it was presumed that foreshock waves would propagate directly into the dayside magnetosphere, observational evidence for sinusoidal Pc3 waves in the downstream of quasi‐parallel shocks is scarce. The transmission of these waves from the foreshock into the magnetosphere remains uncertain. In this paper, we employ a 3D global hybrid simulation at a realistic scale to explore the generation and transmission of the dayside ULF waves under a radial interplanetary magnetic field. Our findings demonstrate that the Pc3 waves are self‐consistently generated in the foreshock region and then transmitted into the magnetosheath and magnetosphere. In the foreshock, the waves are excited at approximately 25 mHz and exhibit right‐handed helicity in the plasma frame, characterizing them as quasi‐parallel fast magnetosonic waves. In the magnetosphere, the fluctuating magnetic field is mainly parallel to the background magnetic field, which indicates the dominant wave modes are compressional. Fluctuations in the magnetosheath show a broader spectrum (10–100 mHz) compared to those in the magnetosphere and foreshock, potentially explaining the little observation of sinusoidal Pc3 waves in the magnetosheath. Additionally, only lower frequency compressional waves (below 30 mHz) are effectively transmitted into the dayside magnetosphere. Our simulation provides critical insights into the interactions between the solar wind and Earth's magnetosphere. Plain Language Summary: Ultralow frequency waves in the Pc3 range, with periods of 10–45 s, are frequently detected in the Earth's magnetosphere. These waves are thought to originate from ion foreshock regions upstream of Earth's quasi‐parallel bow shock. They arise from ion beam instabilities triggered by the interaction between shock‐reflected suprathermal ions and the incoming solar wind. While it was assumed that these Pc3 waves would directly enter the dayside magnetosphere, in‐situ observations of sinusoidal Pc3 waves in the magnetosheath remain rare. This scarcity of evidence has left the mechanisms of their propagation into the magnetosphere unclear. This paper employs a 3D global hybrid simulation at a realistic scale to investigate how the Pc3 waves are transmited through the bow shock, magnetosheath, and into the magnetosphere under a radial interplanetary magnetic field. Our results indicate that the Pc3 waves are self‐consistently generated in the foreshock and transmitted into the magnetosheath and magnetosphere, with only lower frequency compressional waves effectively propagating into the magnetosphere. Fluctuations in the magnetosheath exhibit a broader spectrum compared to those in the magnetosphere and foreshock. Key Points: A 3D global hybrid simulation at a realistic scale has been used to investigate the dayside ULF waves under a radial interplanetary magnetic fieldPc 3 waves are self‐consistently generated at the foreshock region and transmitted into the magnetosheath and magnetosphereFluctuations in the magnetosheath exhibit a broad spectrum, and only lower frequency compressional waves are effectively transmitted into the magnetosphere [ABSTRACT FROM AUTHOR]

The plasmasphere accounts for the majority of the mass of Earth's magnetosphere and contains most of the cold ion (1 eV) population. The plasmasphere is extremely dynamic, undergoing a constant cycle of erosion and refilling. In this paper we perform a statistical study of erosion and refilling rates using 6 years of data from the Van Allen Probes from the beginning of 2013 through the end of 2018. Using in‐situ density measurements derived from the upper hybrid resonance line, we create global maps of the erosion and refilling rates over a wide range of L shells and local times. Sorting the data by L shell, magnetic local time, and distance to the plasmapause, we characterize the absolute and relative rates of erosion and refilling during a variety of geomagnetic conditions. We also examine three case studies of geomagnetic storms and compare their density evolutions during the recovery period. Our results are in agreement with refilling rates found by previous statistical studies using different methods, but somewhat lower than many of the case studies reported. We find median erosion rates of 164, 83, and 43 cm−3/day and refilling rates of 87, 42, and 27 cm−3/day at L = 3, 4 and 5, respectively when Kp ≤ ${\le} $ 3. We also find little local time dependence for both erosion and refilling rates. Plain Language Summary: The plasmasphere is the innermost region of Earth's magnetosphere, and accounts for the majority the magnetosphere's mass. During a geomagnetic storm, the plasmasphere loses mass in process called erosion where plasma is transported toward the sun until it is lost from the magnetosphere. Following the storm, material from the ionosphere slowly refills the plasmasphere in a matter of weeks. In this paper we study average erosion and refilling rates using data from the Van Allen Probes during the years 2013–2018. We create global maps of the erosion and refilling rates over a wide range of longitudes and distances to Earth. We characterize both the absolute and relative rates of erosion and refilling during storms of varying intensities. We also examine three case studies of geomagnetic storms and compare their density evolutions throughout these events. Our results are in agreement with refilling rates found by previous statistical studies, but somewhat lower than many of the case studies reported. At locations of 3, 4, and 5 Earth radii away, we find median refilling rates of 87, 42, and 27 cm−3/day for storms of the lowest intensity. We also find that the erosion and refilling rates are roughly the same for the dawn, day, dusk, and night sides of the planet. Key Points: We perform a statistical study of erosion and refilling rates in the plasmasphere over L shell, local time, and geomagnetic conditionsWe present three case studies which all show similar density evolutions during the recovery periodThe percent rate of change erosion rates are well sorted by distance to the plasmapause, while refilling rates are better sorted by L shell [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]

Geared devices are commonly used to match the operating speed and torque of the power source with the second mover. Such geared devices are usually mechanical gears. As counterparts of the conventional mechanical gears, magnetic gears (MGs) are becoming promising devices, mainly due to the merits of physical isolation between moving parts, no gear lubrication, no mechanical fatigue, inherent overload protection and reduced maintenance, etc. Recently, several new topologies have been proposed to achieve better performances. In this paper, a general review of MGs is presented, including a discussion of the most common and upcoming topologies and a description of the working principle. A comparison of different topologies is carried out in terms of gear ratio and torque density. The main computational techniques generally adopted for coaxial MGs are listed and described. Some key aspects concerning the design, the existed challenges, and potential applications are also discussed. This paper aims to provide a comprehensive overview of the MG for readers working in this field. [ABSTRACT FROM AUTHOR]

The Geostationary Operational Environmental Satellite (GOES)-18, the latest spacecraft from the NOAA GOES-R satellite series, was launched March 1, 2022. As with the previous GOES-16 and GOES-17 satellites, GOES-18 monitors sources of space weather on the Sun and its effects at Earth. NOAA uses GOES data as part of the national space weather forecasts, warnings and alerts to many customers. GOES-18 hosts new magnetometers called the Goddard magnetometers (GMAG) that replace those (called MAG) built by a different vendor on GOES-16 and GOES-17. Like the other GOES satellites, the GOES-18 GMAG provides observations of the geomagnetic field at geostationary orbit (35,786 km), a location that often provides early indication of enhanced space weather activity. In this paper, we review the capabilities of the GOES-18 GMAG along with lessons learned from the GOES-16/17 MAGs. The GOES-R series magnetometer instrument includes two magnetometer sensors (inboard and outboard) mounted along a boom extended from the spacecraft. As with the previous magnetometers, the GMAG sensors are three-axis fluxgates sampling the geomagnetic field at 10 samples/second, with the data low-pass filtered with a 2.5 Hz cutoff. On-orbit analysis demonstrates that the GOES-18 GMAG is a highly stable instrument showing little variations between the inboard and outboard sensors either diurnally or over multiple days. A nearly 2.5 months collocation between GOES-18 and GOES-17 (136.8°W and 137.2°W) allowed direct cross-satellite comparisons that was unprecedented for GOES satellites. Differences between the on orbit performance of the GMAG and MAG sensors are attributed to thermal stability issues observed on the GOES-17 MAG (also observed on the GOES-16 MAG). The cross-satellite analysis during the collocation interval, along with inboard/outboard sensor comparisons and comparisons to models, suggests that the GOES-18 GMAG meets the NOAA mission requirement of ± 1 nT accuracy, excluding arcjet firing periods. Arcjet firing periods were also excluded in performance analysis for GOES-16/17. [ABSTRACT FROM AUTHOR]

We combine wavelet analysis and data fusion to investigate geomagnetically induced currents (GICs) on the Mäntsälä pipeline and the associated horizontal geomagnetic field, BH, variations during the late main phase of the 17 March 2013 geomagnetic storm. The wavelet analysis decomposes the GIC and BH signals at increasing "scales" to show distinct multi‐minute spectral features around the GIC spikes. Four GIC spikes >10 A occurred while the pipeline was in the dusk sector—the first sine‐wave‐like spike at ∼16 UT was "compound." It was followed by three "self‐similar" spikes 2 hr later. The contemporaneous multi‐resolution observations from ground‐(magnetometer, SuperMAG, SuperDARN), and space‐based (AMPERE, Two Wide‐Angle Imaging Neutral‐atom Spectrometers) platforms capture multi‐scale activity to reveal two magnetospheric modes causing the spikes. The GIC at ∼16 UT occurred in two parts with the negative spike associated with a transient sub‐auroral eastward electrojet that closed a developing partial ring current loop, whereas the positive spike developed with the arrival of the associated mesoscale flow‐channel in the auroral zone. The three spikes between 18 and 19 UT were due to bursty bulk flows (BBFs). We attribute all spikes to flow‐channel injections (substorms) of varying scales. We use previously published MHD simulations of the event to substantiate our conclusions, given the dearth of timely in‐situ satellite observations. Our results show that multi‐scale magnetosphere‐ionosphere activity that drives GICs can be understood using multi‐resolution analysis. This new framework of combining wavelet analysis with multi‐platform observations opens a research avenue for GIC investigations and other space weather impacts. Plain Language Summary: Geomagnetically Induced Currents (GIC) are produced by complex interaction between the Earth's magnetic field and geological composition during intense geomagnetic storms. These two parameters are often related in frequency domain. In this paper, we analyze the GIC signal from the Finnish natural gas pipeline recorded at Mäntsälä during the 17 March 2013 geomagnetic storm. Four spikes >10 A were recorded between 4:30 and 9:00 p.m. local time. We use wavelet analysis to learn about the frequencies of GIC spikes and then systematically investigate the observations from ground to space (ground‐up approach) to learn what links activity in space to the GICs. Wavelet analysis highlights areas ranging from <1 min to >30 min, which indicates that higher frequency fluctuations are accompanied with longer duration disturbance. Multi‐platform observations help us interpret the physical meaning of the multi‐minute (or multi‐scale) area in the wavelet plot. We find that multi‐scale activity in the magnetosphere and ionosphere, created by fast earthward‐flowing particles (magnetotail mesoscale plasma flows), ultimately drove the significant GIC spikes. This new perspective enabled us to link the magnetospheric activity to GICs through observations and previously published simulations and pave a path for future research. Key Points: Wavelet analysis of GICs at Mäntsälä on 17 March 2013 reveals two features—Pi1/Pi2 pulsations superposed on longer duration disturbancesWavelet decomposition of the GIC and BH signals is consistent with multi‐scale magnetosphere‐ionosphere activity around GIC spikesPi2 pulsations and data fusion suggest mesoscale flow channels (substorm injections) were the underlying cause of four GICs >10 A [ABSTRACT FROM AUTHOR]

The polar cap magnetic activity index (PC) was approved by IAGA as an index characterizing the solar wind energy input into the magnetosphere. Relation of the PC index to solar wind parameters and solar activity during 23/24 solar cycles has been studied in paper (Troshichev et al., 2021, https://doi.org/10.1029/2020JA028491). The paper was commented by Dr. Stauning, who states that results obtained in the study are based on erroneous data presented on web site http://pcindex.org. According to Dr. Stauning, the following invalidities served as a reason for this assertion: incorrect determination of quiet daily curve (QDC), taken as reference level for counting the PC index value, and incorrect QDC amplitudes, incorrect yearly average values of PC index (and EKL field), incorrect methods of the analysis. In our answer we argue the correctness of our analysis and resulted conclusions. Plain Language Summary: The quality of the IAGA endorsed PC index is supplied by choice of proper quiet daily variation (QDC), which makes it possible to account the effect of irregular solar UV irradiation related to solar flares. This special features of the PC index derivation made it possible to reveal the correlation between the QDC amplitude and the solar flares intensity in course of solar 23/24 cycle. The value of the yearly PC index may be estimated with use of median or mean PC quantities, resulting in essential discrepancy of the deduced yearly PC index values. The relative values of median quantities were used in the analysis. The preliminary PCS indices turned out to be incorrectly evaluated in case of 4 months in 2011, but this circumstance did not affect the general regularity of PCN/PCS changes over period 1997–2019. Divergence between values of the corresponding PCN and PCS indices, typical of solstice seasons in periods of high solar activity, is conditioned by different conductivity of ionosphere in summer and winter polar caps, not by quality of the PCN or PCS indices. Definitive PC indices have demonstrated the perfect agreement with preliminary PC indices validating the conclusions made in (Troshichev et al., 2021, https://doi.org/10.1029/2020JA028491). Key Points: Claims (Stauning, 2022) of using the unapproved polar cap indices in study (Troshichev et al., 2021) are baselessYearly QDC‐X and QDC_Y values demonstrated agreed alterations at stations Thule and Vostok in 1998–2019The relative yearly mean values derived via hourly median quantities used in analysis provide the same result as hourly mean quantities [ABSTRACT FROM AUTHOR]

Universal Time (UT) variations in many magnetospheric state indicators and indices have recently been reviewed by Lockwood and Milan (2023, https://doi.org/10.3389/fspas.2023.1139295). Key effects are introduced into magnetospheric dynamics by the eccentric nature of Earth's magnetic field, features that cannot be reproduced by a geocentric field model. This paper studies the UT variation in the occurrence of substorm onsets and uses a simple Monte‐Carlo model to show how it can arise for an eccentric field model from the effect of the diurnal motions of Earth's poles on the part of the geomagnetic tail where substorms are initiated. These motions are in any reference frame that has an X axis that points from the center of the Earth to the center of the Sun and are caused by Earth's rotation. The premise behind the model is shown to be valid using a super‐posed epoch study of the conditions leading up to onset. These studies also show the surprising degree of preconditioning ahead of the growth phase that is required, on average, for onset to occur. A key factor is the extent to which pole motions caused by Earth's rotation influence the near‐Earth tail at the relevant X coordinate. Numerical simulations by a global MHD model of the magnetosphere reveal the effect required to generate the observed UT variations and with right order of amplitude, albeit too small by a factor of about one third. Reasons why this discrepancy may have arisen for the simulations used are discussed. Plain Language Summary: Earth's magnetic field is eccentric in that the main magnetic (dipole) axis does not pass through the center of the Earth. This introduces a wobble into many aspect of near‐Earth space (the "magnetosphere") as Earth rotates. Many consequences of this have been noted in previous papers. This paper investigates the effect of the eccentricity on the phenomenon of magnetospheric substorms. It is shown that the explosive releases of energy stored in the tail of the magnetosphere are more likely to start ("onset") at some Universal Times (and therefore geographic longitudes) than others and an explanation of why is provided. Key Points: Universal Time (UT) effects in the magnetosphere are caused by the eccentric nature of Earth's intrinsic magnetic fieldThere is a UT dependence of the open flux (and hence also the integrated magnetopause reconnection voltage) needed to trigger substorm onsetGrowth phases that lead to substorm onset show considerable preconditioning by prior reconnection [ABSTRACT FROM AUTHOR]

Ultralow frequency (ULF) waves in the Pc5 band are ubiquitous in the inner magnetosphere and can impact radiation belt dynamics by interacting with electrons through drift or drift‐bounce resonance. In this paper, based on ∼ 19 years of Cluster measurements, we perform a comprehensive study of the three‐dimensional distribution of poloidal, toroidal, and compressional ULF waves from L = 4 to 10, for magnetic latitudes (MLAT) up to Ultralow frequency ±50°, and in all magnetic local times (MLT). The distribution of the Pc5 ULF wave power is found to vary greatly as a function of L and MLT. For all L and MLT sectors, wave power of the poloidal and toroidal modes of the magnetic field increase with increasing |MLAT|, while the compressional mode decreases with increasing |MLAT|. The dawn–dusk asymmetries of wave power in poloidal and toroidal modes are more pronounced at higher |MLAT|. Furthermore, the wave power for Kp > 2 is approximately 2.93, 3.21, and 3.42 times greater than the wave power for Kp ≤ 2, respectively for compressional, poloidal and toroidal components. The information on the latitudinal distributions of ULF waves presented in this paper is important for future investigations on the radial diffusion process of radiation belt electrons with non‐90° pitch angles while they bounce away from the magnetic equator. Key Points: About 19 years of Cluster measurements are used to study the latitudinal distribution of magnetic Pc5 pulsationsWave power of the poloidal and toroidal modes increases with increasing |MLAT|, while compressional mode decreases with increasing |MLAT|The statistical results can be used for the study of radial diffusion of radiation belt electrons with non‐90° pitch angles [ABSTRACT FROM AUTHOR]

During its polar orbits around Jupiter, Juno often crosses the boundaries of the Jovian magnetosphere (namely the magnetopause and bow shock). From the boundary locations, the upstream solar wind dynamic pressure can be inferred, which in turn illustrates the state of compression or relaxation of the system. The aim of this study is to examine Jovian radio emissions during magnetospheric compressions, in order to determine the relationship between the solar wind and Jovian radio emissions. In this paper, we give a complete list of bow shock and magnetopause crossings (from June 2016 to August 2022), and the associated solar wind dynamic pressure and standoff distances inferred from Joy et al. (2002, https://doi.org/10.1029/2001JA009146). We then select two sets of magnetopause crossings with moderate to strong compression of the magnetosphere for two case studies of the response of the Jovian radio emissions. We confirm that magnetospheric compressions lead to the activation of new radio sources. Newly activated broadband kilometric emissions are observed almost simultaneously with compression of the magnetosphere, with sources covering a large range of longitudes. Decametric emission sources are seen to be activated more than one rotation later only at specific longitudes and dusk local times. Finally, the activation of narrowband kilometric radiation is not observed until the magnetosphere is in its expansion phase. Key Points: This paper provides a list of the Jovian magnetosphere boundary crossings by the Juno spacecraft from June 2016 to August 2022Jovian magnetospheric compressions lead to increased bKOM radio emissions (immediately) and DAM on the dusk sector (more than one rotation later)nKOM radio emission appears later during relaxation phase of the compression [ABSTRACT FROM AUTHOR]

This paper describes the development of a magnetic attitude control subsystem for a 2U cubesat. Due to the presence of gravity-gradient torques, the satellite dynamics are open-loop unstable near the desired pointing configuration. Nevertheless, the linearized time-varying system is completely controllable, under easily verifiable conditions, and the system’s disturbance rejection capabilities can be enhanced by adding air drag panels exemplifying a beneficial interplay between hardware design and control. In this paper, conditions for the complete controllability for the case of a magnetically controlled satellite with passive air drag panels are developed, and simulation case studies with the linear quadratic regulator and model predictive control designs applied in combination with a nonlinear time-varying input transformation are presented to demonstrate the ability of the closed-loop system to satisfy mission objectives despite disturbance torques. [ABSTRACT FROM AUTHOR]

The theta aurora is reproduced by global simulation. First, we construct a solution for the stationary northward interplanetary magnetic field (IMF) forming the separatrices, the separators, the nulls, and the stemlines. From the drawing of last‐closed field lines, the overall structure under this condition is summarized as the northern lobe is generated by a separatrix emanating from the southern null. In this paper, all variations are antisymmetric in the southern hemisphere. Afterward, the IMF By is switched to reproduce the theta aurora. The ionospheric theta aurora is reproduced as closed magnetic field regions. The polar cap is divided to old and new parts, by the theta bar. In the magnetosphere, two dayside nulls occur corresponding to the new IMF and two nulls corresponding to the old IMF retreat tailward. The four nulls form a structure connected by four separators, constructing the magnetospheric topology corresponding to the theta aurora. In this topology, old and new nulls in the southern hemisphere generate old and new lobes in the northern hemisphere. Each lobe is projected onto northern old and new polar caps. The origin of the theta bar is the stagnating closed magnetic field region that occurs between old and new lobes. Separator reconnection occurs between the old lobe in the southern and the new lobe in the northern hemispheres, reducing southern old polar caps. This is the cause of the movement of the theta bar. The theta aurora is the phenomenon that demonstrates the existence of the null‐separator structure. Key Points: The theta aurora is an image of the magnetospheric null‐separator structure projected to the virtual mirror in the ionosphereNorthern new and old lobes are respectively generated from new dayside and old retreating nulls in the southern hemisphereThe theta bar is the projection of stagnating closed magnetic field regions accumulating at the interface between old and new lobes [ABSTRACT FROM AUTHOR]

We present the first direct evidence of an in situ excitation of drift‐compressional waves driven by drift resonance with ring current protons in the magnetosphere. Compressional Pc4–5 waves with frequencies of 4–12 mHz were observed by the Arase satellite near the magnetic equator at L ∼ 6 in the evening sector on 19 November 2018. Estimated azimuthal wave numbers (m) ranged from −100 to −130. The observed frequency was consistent with that calculated using the drift‐compressional mode theory, whereas the plasma anisotropy was too small to excite the drift‐mirror mode. We discovered that the energy source of the wave was a drift resonance instability, which was generated by the negative radial gradient in a proton phase space density at 20–25 keV. This proton distribution is attributed to a temporal variation of the electric field, which formed the observed multiple‐nose structures of ring current protons. Plain Language Summary: During magnetic storms and substorms, energetic ions are sporadically injected into the geospace, which distorts the stable population and velocity distributions of ions in space. At these moments, various plasma instabilities lead to ultra‐low frequency (ULF) wave excitations. The lowest‐frequency waves in the ULF range have a wavelength comparable to the size of the Earth and are typically analyzed using magnetohydrodynamic principles. This approach considers the plasma environment using macroscale parameters such as pressure and density. In this paper, we report a spacecraft observation of a broadband compressional ULF wave that cannot be interpreted using magnetohydrodynamics. Such waves have rarely been reported and analyzed; however, their interaction with energetic ions is important to understand magnetospheric energy dynamics. The plasma conditions were described using the kinetic theory, which involves particle velocity distributions. We observed that a drift resonance occurred between the energetic protons and waves, while the gradient instability condition was satisfied for a part of time. Therefore, we concluded that the wave was in a drift‐compressional mode excited through drift resonance and gradient instability. The interpretation of compressional waves via satellite observations of energetic ions has been receiving increasing attention to understand their excitation mechanism. Key Points: Pc4–5 compressional ultra‐low frequency waves with an azimuthal wave number of −130 were observed in the nose structure on dusksideTheoretically predicted values of drift‐compressional mode frequency match the observed wave frequencyBoth radial ion temperature gradient and drift resonance of 20–25 keV protons serve as energy sources of the wave [ABSTRACT FROM AUTHOR]

Theoretical analysis has revealed a specific resonance that shares the same condition as Landau resonance, but instead involves wave electromagnetic fields rather than traditionally electrostatic fields. While this resonance, referred to as electromagnetic Landau resonance due to its properties, is considered significant for magnetospheric dynamics, rare reports or evaluations based on observations have been made thus far. Here, we present an event detected by the Magnetospheric Multiscale mission near the dayside magnetopause. During this event, ∼748‐eV protons are observed to be in resonance with a wave. Detailed data analysis demonstrates the resonant velocity closely matches the wave's parallel phase speed, which, combined with the significant work done by wave perpendicular electric field, confirms this interaction as electromagnetic Landau resonance. Further investigation indicates these protons are being secularly accelerated within this resonance. Consequently, our observations provide the first empirical evidence supporting the previously suggested theoretical importance of the electromagnetic Landau resonance. Plain Language Summary: The electromagnetic Landau resonance shares the same resonance condition as the normal Landau resonance, but differs in that it involves the electromagnetic components of wave fields instead of the electrostatic components found in the case of the latter. Although it has been examined in theories and confirmed to occur in space plasmas experimentally, this resonance, especially the accompanying evolution of particle velocity distributions, has yet to be evaluated quantitatively through spacecraft observations. In this paper, we report the first observation of this resonance obtained by the Magnetospheric Multiscale mission near the dayside magnetosphere. In the reported case, protons of ∼400–1,000 eV are found to be in resonance with a wave. A more detailed examination of the observed fields and protons shows the corresponding resonant velocity is nearly identical to the wave's parallel phase speed. This observation, combined with the significant work done by wave perpendicular electric field, conclusively confirms the observed interaction as the electromagnetic Landau resonance. Further investigation indicates the protons are secularly accelerated by the wave via this resonance. Hence, our observations provide empirical evidence supporting the previously suggested theoretical significance of the electromagnetic Landau resonance. Key Points: MMS observations of electromagnetic Landau resonance near the dayside magnetopause are presentedThis resonance follows the same condition as the Landau resonance, but modulates particles via the electromagnetic components of wave fieldsAnalysis of the observed fields and protons provide conclusive evidence for this resonance accelerating protons [ABSTRACT FROM AUTHOR]

The magnetospheric systems of ice giants, as the ideal and the unique template of a typical class of exoplanets, have not been sufficiently studied in the past decade. The complexity of these asymmetric and extremely dynamic magnetospheres provides us a great chance to systematically investigate the general mechanism of driving the magnetospheres of such common exoplanets in the Universe, and the key factors of influencing the global and local magnetospheric structures of this type of planets. In this paper, we discuss the science return of probing magnetospheric systems of ice giants for the future missions, throughout different magnetospheric regions, across from the interaction with upstream solar wind to the downstream region of the magnetotail. We emphasize the importance of detecting the magnetospheric systems of ice giants in the next decades, which enables us to deeply understand the space enviroNMent and habitability of not only the ice giants themselves but also the analogous exoplanets which are widely distributed in the Universe. [ABSTRACT FROM AUTHOR]

This paper describes the instrumentation and the first results of an upper atmospheric observing project conducted in New Zealand. We operate an all-sky aurora camera and a 64-Hz sampling induction magnetometer at Middlemarch, as well as 1-Hz sampling fluxgate magnetometers which have been operative at three stations in New Zealand, Middlemarch, Eyrewell and Te Wharau. Green and red auroras corresponding to the 557.7 nm and 630.0 nm emissions, respectively, were observed on the night of 5 August 2019. Pc1 pulsations were observed in the frequency range of ~ 0.2–1 Hz before and after a small (minimum Dst = − 40 nT) geomagnetic storm during 4–6 October 2020. Before the geomagnetic storm, Pc1 pulsations with several center frequencies were observed regardless of local time. During the recovery phase, an IPDP (interval of pulsations of diminishing period) type of Pc1 and four subsequent intervals of Pc1s were detected. The Ionospheric Alfvén Resonator (IAR) was also identified with spectral resonance structures during this magnetic storm. Lower harmonic modes of the IAR were present throughout the local nighttime, but higher harmonic modes with frequency of 5–15 Hz seemed to disappear at the onset time of substorms. This is the first report of the IAR at such a high frequency range and this is the first IAR observation in the southern hemisphere. Examples of applying cross-phase analysis to observation data of fluxgate magnetometers are also given. [ABSTRACT FROM AUTHOR]

The earth’s magnetosphere is an intricate input–output system, where the inputs are the solar wind parameters and the output measure are the geomagnetic. The disturbance storm time (DST) index is one such quantity measure for the intensity of disturbance in the geomagnetic field due to the magnetic storm. The geomagnetic activities have catastrophic effects on several communication networks and harmful for biological livings. Therefore, it is significant to develop a model for the prediction of disturbance in the geomagnetic field. This paper presents linear as well as nonlinear parametric techniques to model the complex magnetosphere dynamics. Neural network (NN)-based modeling techniques, such as feed-forward NN (FFNN), NN integrated with nonlinear autoregression with exogenous (NARX) inputs, adaptive neuro-fuzzy inference system (ANFIS), and recurrent NN are developed for the prediction of the magnetic storm. Global search algorithms, such as particle swarm optimization and genetic algorithm, also train the developed FFNNs. All the models are trained on 15 years’ real-time series data of solar wind parameters and DST index on a frequency of 1 h. The accuracy of the predicted DST index for multiple intensity levels of the magnetic storm using all developed linear and nonlinear modeling techniques is presented, compared, and analyzed thoroughly. The performance of NN integrated with NARX inputs and ANFIS is higher than rest of methods developed in the paper. Both techniques have the capability to predict mild, moderate, and intense magnetic storm with high degree of accuracy. The comparative analysis with state of the art shows the enhanced accuracy and robustness of developed models in this paper. [ABSTRACT FROM AUTHOR]

Use of low static magnetic fields for nuclear magnetic resonance (NMR) signal detection remains a challenge due to low signal-to-noise ratio, low energy difference between energy levels, and less spin transitions due to limited availability of spins. Despite these challenges, different measurement techniques based on low static magnetic fields, stray magnetic fields, and non-uniform fields have been implemented. In this paper, an approach toward using low static fields generated by permanent magnets for portable magnetic resonance applications is described. Finite element simulation models of different magnet geometries are used to develop an estimate of the magnetic field distribution exterior to the magnet. A concentric ring magnet geometry is selected to obtain flexible control of localized regions of uniform magnetic field. An estimate of the NMR voltage for different magnet sizes and orientations is presented. It is expected that the findings of this paper would be valuable for design of future portable magnetic resonance systems. [ABSTRACT FROM AUTHOR]

Abstract: This work is a continuation of paper [1], in which we discussed some incorrect approaches to the identification of large-scale types of solar wind and associated incorrect conclusions in the analysis of solar-terrestrial physics data. In this paper, we analyze the lists of 28 events of coronal mass ejection (CME) and 31 events of corotating interaction region (CIR) in 2013-2016 used by Shen et al. [2] to compare the responses of the Earth’s radiation belts to various interplanetary drivers. The interpretation of solar wind types in these lists differs both from our catalog [3] for Sheath, ICME, and CIR and from the catalog by Richardson and Cane [4] for CME. In addition, the authors of paper [2] do not distinguish the Sheath- and ICME-induced magnetic storms and include them in the general type of CME-induced storms. Our analysis has shown that, among the 28 events of CME-induced storms mentioned, 16 events belong to Sheath, 2 events to MC, 4 events to Ejecta, 2 events to CIR, and 4 events to undisturbed solar wind with shocks. The catalog [4], which also does not distinguish the Sheath and ICME, contains 18 of the 28 events presented in paper [2]. Among 31 CIR events presented by the authors of paper [2], according to our analysis, 25 events belong to CIR, 2 events to Sheath, and 4 events to undisturbed solar wind. In catalog [4], one of the 31 CIR events from paper [2] is presented as CME. Since the properties of CIR and Sheath compression regions are close, the conclusions of the authors of paper [2] on the properties of CIR-induced storms are only slightly distorted by the incorrect identification of stream types, whereas the conclusions concerning the CME-induced storms, which more than by a half represent the Sheath-induced storms, seem incorrect to us. [ABSTRACT FROM AUTHOR]

Although cogging torque in magnetic gears (MGs) has been studied, the additional degree of freedom inherent to MGs makes it unclear exactly what is defined as the cogging torque of a MG. Although MGs generally have relatively smooth torque transfer characteristics, this paper reveals that when the gear is used in an up-speed configuration, cogging effects may be amplified under startup conditions. This paper distinguishes between two kinds of cogging torque in MGs, termed the synchronous cogging torque and the true cogging torque. Calculation of the true cogging torque is more difficult than the synchronous cogging torque, but an approximation to the true cogging torque can be obtained using the synchronous cogging torque. The theory is verified experimentally and supported further by results from dynamic simulations. The impact on magnetically geared machines is also considered. [ABSTRACT FROM AUTHOR]

A variety of plasma waves have been detected in the vicinity of the magnetopause by various spacecraft missions. In this paper, utilizing high-resolution data from the Magnetospheric Multiscale (MMS) mission, we present new observations of simultaneous lower hybrid and ion solitary waves in the dusk flank region of Earth's magnetosphere. All four MMS spacecraft consistently observed this wave activity during their traversal from Earth's magnetosphere to the magnetosheath. Our analysis suggests that the lower hybrid drift waves, driven by lower-hybrid drift instability, were observed in correlation with density gradients. Furthermore, the analysis indicates that the entire ion bulk population drifts, which drives ion solitary waves. It is found that these waves play a crucial role in particle heating in the dusk flank region of Earth's magnetosphere. [ABSTRACT FROM AUTHOR]

Today's challenge for space weather research is to quantitatively predict the dynamics of the magnetosphere from measured solar wind and interplanetary magnetic field (IMF) conditions. Correlative studies between geomagnetic storms (GMSs) and the various interplanetary (IP) field/plasma parameters have been performed to search for the causes of geomagnetic activity, which are important for space weather predictions. In this paper we have found relation between solar activity and geomagnetism during the solar cycle-24. Geomagnetic storms (GMSs) were less during the observed cycle, no severe and great storms had occurred during that cycle. Yearly occurrence of GMSs does not exactly match with phase of solar cycle-24. Similarly occurrences of Coronal mass ejection (CMEs) also do not exactly follow the phase of solar cycle but yearly occurrence of GMSs follow the yearly occurrence of Halo CMEs. Consequently, halo CMEs are responsible for the occurrence of GMSs during the solar cycle-24. The behavior of the total average interplanetary magnetic field (IMF) Btotal, Southward component of IMF (Bz), Solar wind temperature, Solar wind density, Solar wind dynamic pressure, Solar wind velocity (V), and Ey along with geomagnetic storms (Dst index) have been analyzed in this paper. Relation of Dst with Btotal, Bz, Speed V and Ey has been found good during the cycle-24. [ABSTRACT FROM AUTHOR]

Jupiter has the most complex and energetic radiation belts in our Solar System and one of the most challenging space environments to measure and characterize in-depth. Their hazardous environment is also a reason why so many spacecraft avoid flying directly through their most intense regions, thus explaining how Jupiter's radiation belts have kept many of their secrets so well hidden, despite having been studied for decades. In this paper we argue why these secrets are worth unveiling. Jupiter's radiation belts and the vast magnetosphere that encloses them constitute an unprecedented physical laboratory, suitable for interdisciplinary and novel scientific investigations: from studying fundamental high energy plasma physics processes which operate throughout the Universe, such as adiabatic charged particle acceleration and nonlinear wave-particle interactions, to exploiting the astrobiological consequences of energetic particle radiation. The in-situ exploration of the uninviting environment of Jupiter's radiation belts presents us with many challenges in mission design, science planning, instrumentation, and technology. We address these challenges by reviewing the different options that exist for direct and indirect observations of this unique system. We stress the need for new instruments, the value of synergistic Earth and Jupiter-based remote sensing and in-situ investigations, and the vital importance of multi-spacecraft in-situ measurements. While simultaneous, multi-point in-situ observations have long become the standard for exploring electromagnetic interactions in the inner Solar System, they have never taken place at Jupiter or any strongly magnetized planet besides Earth. We conclude that a dedicated multi-spacecraft mission to Jupiter is an essential and obvious way forward for exploring the planet's radiation belts. Besides guaranteeing numerous discoveries and huge leaps in our understanding of radiation belt systems, such a mission would also enable us to view Jupiter, its extended magnetosphere, moons, and rings under new light, with great benefits for space, planetary, and astrophysical sciences. For all these reasons, in-situ investigations of Jupiter's radiation belts deserve to be given a high priority in the future exploration of our Solar System. This article is based on a White Paper submitted in response to the European Space Agency's call for science themes for its Voyage 2050 programme. [ABSTRACT FROM AUTHOR]

The magnetopause standoff distance characterizes global magnetospheric compression and deformation in response to changes in the solar wind dynamic pressure and interplanetary magnetic field orientation. We cannot derive this parameter from in situ spacecraft measurements. However, time series of the magnetopause standoff distance can be obtained in the near future using observations by soft X‐ray imagers. In two companion papers, we describe methods of finding the standoff distance from X‐ray images. In Part 1, we present the results of MHD simulations which we use for the calculation of the X‐ray emissivity in the magnetosheath and cusps. Some MHD models predict relatively high density in the magnetosphere, larger than observed in the data. Correcting this, we develop magnetospheric masking methods to separate the magnetosphere from the magnetosheath and cusps. We simulate the X‐ray emissivity in the magnetosheath for different solar wind conditions and dipole tilts. Plain Language Summary: The highly dynamic solar wind continuously bombards the Earth's magnetosphere, which changes shape in response. The magnetopause is the outer boundary of the magnetosphere, which is known to move. We are limited in our knowledge of the overall shape of the magnetopause, as current in situ measurements can only tell us about any change in the magnetopause at one specific location. Spacecraft carrying soft X‐ray imagers, however, will soon revolutionize our understanding by monitoring large areas of the magnetopause as the solar wind varies. In this first of a series of two papers, we simulate X‐ray emissions in the vicinity of the Earth using two magnetohydrodynamic models, and for two case studies with vastly different incoming solar wind conditions. In a subsequent paper, we examine methods how to extract the magnetopause shape from the simulated X‐ray images. Key Points: The SMILE mission will carry soft X‐ray imager onboardMagnetospheric masking methods separate the magnetosphere from the magnetosheath and cuspsWe make magnetospheric masks using threshold conditions and flowlines [ABSTRACT FROM AUTHOR]

The paper summarizes the issues related to relationships between the PC index and magnetic disturbances: threshold level of the PC index required for the disturbances beginning, delay time in response of magnetic substorms and storms to the PC index growth, relation of PC index to magnetospheric field-aligned currents in course of substorm, different types of magnetic substorms (isolated, expanded, delayed, sawtooth) and magnetic storms (classic, pulsed and composite) and their relation to different regularities in the PC index alterations, linear dependence of the substorm and storm intensities on value of the preceding of PC index, special features of magnetic activity in the winter and summer polar caps, variations of PC index and magnetic disturbances in course of the 23/24 solar activity cycles. New aspects that have arisen due to the PC index application are concerned with the threshold-dependent mode of the substorm development and regular repeateness of sawtooth substorms occurring under conditions of steady powerful EKL field. The experimental results examined in the paper are indicative that the PC index serves as an indicator of the solar wind energy which comes in the magnetosphere and then realizes in the form of magnetosphere disturbances. This paper follows the review of Troshichev (Front Astron Space Sci 9:1069470, 2022), where the relationships between the solar wind electric field EKL and PC index have been examined. [ABSTRACT FROM AUTHOR]

This paper is concerned with the condition for the development of ballooning instability in the dipole Earth's magnetosphere. Under investigation is the dependence of the ratio of the radial and azimuthal wave vector components squared on the wave frequency squared ω 2 . It is shown that this dependence is depicted by continuous curve (the dispersion curve). The part of the dispersion curve with ω 2 > 0 corresponds to the slow magnetosonic mode modified by the coupling with the Alfvén mode, while the part with ω 2 < 0 corresponds to the ballooning instability. The instability appears at some critical ratio of the radial and azimuthal wave vector components, the growth rate reaches the maximum value where this ratio is zero. The instability threshold is determined depending on the β parameter and the pressure gradient when the coupling of the slow and Alfvén modes is taken into account. On a given magnetic shell, at a given β value, large pressure gradient favors the instability, and vice versa, at a given pressure gradient, a large β favors instability. It is shown that in the unstable mode, the compressional magnetic field component has a phase shift with respect to the radial component. This can be used to detect unstable ballooning modes during observations in the Earth's magnetosphere. [ABSTRACT FROM AUTHOR]

The Plasma Environment Modeling in the Earth's Magnetosphere (PEMEM) is a European Space Agency activity supporting the development of a new specification model for the spacecraft surface charging risk assessment. This paper presents a description of the basic model version: the PEMEM percentile model. The model is intended to be used for space missions with near‐equatorial orbits. The model is based on the Van Allen Probes particle measurements inside the geostationary orbit. The model's primary input is a planned spacecraft trajectory. It outputs statistical characteristics of the plasma environment which are expected to be encountered during a mission lifetime. These characteristics include differential electron and proton flux percentiles for a set of energies (percentile spectra), and percentiles of the integrated electron flux. The model covers the energy range of 1–100 keV for electrons and 40 eV–51 keV for protons. Since extreme spacecraft charging usually occurs in the eclipse, the same characteristics can be separately output for the periods when the spacecraft is shadowed by the Earth. Key Points: The new specification model of cis‐GEO near‐equatorial plasma environment aimed at the surface charging risk assessment is presentedThe model covers the energy ranges 1–100 keV for electrons and 50 eV–50 keV for protonsFor a given orbital scenario, the model outputs flux percentiles that are expected to be encountered during the mission lifetime [ABSTRACT FROM AUTHOR]

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, v[sub α] (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: rα[sub PMAF] =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 FROM AUTHOR]

The paper presents a description of low-frequency nonlinear dust-acoustic waves in the dusty magnetosphere of Saturn, which contains two types of electrons (hot and cold) following the kappa distribution, magnetospheric ions, and charged dust particles. The Zakharov–Kuznetsov equation for the corresponding conditions is derived, describing the nonlinear dynamics of dust-acoustic waves in the case of low frequencies and a pancake-shaped wave packet along the external magnetic field. It is shown that, under the conditions of Saturn's magnetosphere, solutions of the Zakharov–Kuznetsov equation exist in the form of one-dimensional and three-dimensional solitons. Possible observations of such solitons in future space missions are discussed. [ABSTRACT FROM AUTHOR]