Magnetosheath jets are localized fast flows with enhanced dynamic pressure. When they supermagnetosonically compress the ambient magnetosheath plasma, a bow wave or shock can form ahead of them. Such a bow wave was recently observed to accelerate ions and possibly electrons. The ion acceleration process was previously analyzed, but the electron acceleration process remains largely unexplored. Here

The editors thank the 2019 peer reviewers

When a magnetosheath jet (localized dynamic pressure enhancements) compresses ambient magnetosheath at a (relative) speed faster than the local magnetosonic speed, a bow wave or shock can form ahead of the jet. Such bow waves or shocks were recently observed to accelerate particles, thus contributing to magnetosheath heating and particle acceleration in the extended environment of Earth’s bow shock

In this study, equatorial electrojets (EEJs) simulated by the Thermosphere‐Ionosphere Electrodynamics General Circulation Model (TIE‐GCM) were compared with those observed by ground‐based magnetometers and the Challenging Minisatellite Payload (CHAMP) satellite. Simulations were performed with or without non‐migrating tidal forcing at the lower boundary and in the frame of the international geomagnetic

This work is a continuation of our previous articles (Yermolaev et al . 2015; 2017; 2018), which describe the average temporal profiles of interplanetary plasma and field parameters in large‐scale solar‐wind (SW) streams: corotating interaction regions (CIRs), interplanetary coronal mass ejections (ICMEs including both magnetic clouds (MCs) and ejecta), and sheaths as well as interplanetary shocks

The NASA Global‐scale Observations of the Limb and Disk (GOLD) mission has flown an ultraviolet‐imaging spectrograph on SES‐14, a communications satellite in geostationary orbit at 47.5° W longitude. That instrument observes the Earth’s far ultraviolet (FUV) airglow at ~134‐162 nm using two identical channels. The observations performed include limb scans; stellar occultations; and images the sunlit

The moon Dione orbits Saturn at 6.2 Saturn radii $R_S$ deep in the Kronian magnetosphere. In‐situ studies of the moon‐magnetosphere interaction processes near Dione were possible with the Cassini/Huygens mission which flew by close to Dione five times at distances between 99 km and 516 km. In addition, Cassini crossed Dione’s L‐shell more than 400 times between 2004 and 2017 and documented the variability

In the diffusion region of magnetotail reconnection, particle distributions are highly structured, exhibiting triangular shapes and multiple striations that deviate dramatically from the Maxwellian distribution. Fully kinetic simulations have been demonstrated to be capable of producing the essential structures of the observed distribution functions, yet are computationally not feasible for 3D global

Magnetopause Kelvin‐Helmholtz (KH) waves are believed to mediate solar wind plasma transport via small‐scale mechanisms. Vortex‐induced reconnection (VIR) was predicted in simulations and recently observed using NASA's Magnetospheric Multiscale (MMS) mission data. Flux Transfer Events (FTEs) produced by VIR at multiple locations along the periphery of KH waves were also predicted in simulations but

No abstract is available for this article.

In the Earth's inner magnetosphere, charged particles can be accelerated and transported by ultralow frequency (ULF) waves via drift resonance. We investigate the effects of magnetospheric convection on the nonlinear drift resonance process, which provides an inhomogeneity factor S to externally drive the pendulum equation that describes the particle motion in the ULF wave field. The S factor, defined

During geomagnetically quiet and solar minimum conditions, spatial variations of the early morning thermosphere‐ionosphere (TI) system are expected to be mainly governed by wave dynamics. To study the post‐midnight dynamical coupling, we investigated the early morning equatorial ionization anomaly (EIA) using Global‐scale Observations of the Limb and Disk (GOLD) measurements of OI‐135.6 nm nightglow

We report the observation of solar wind‐magnetosphere‐ionosphere interactions using a series of flux transfer events (FTEs) observed by MMS located near the dayside magnetopause on 18 December 2017. The FTEs were observed to propagate duskward and either southward or slightly northward, as predicted under duskward and southward IMF. The Cooling model also predicted a significant dawnward propagation

Plasma structures with enhanced dynamic pressure, density or speed are often observed in Earth's magnetosheath. We present a statistical study of these structures, known as jets and fast plasmoids, in the magnetosheath, downstream of both the quasi‐perpendicular and quasi‐parallel bow shocks. Using measurements from the four Magnetospheric Multiscale (MMS) spacecraft and OMNI solar wind data from 2015–2017

This study analyzes strong sporadic E‐layer (Es) formation in Boa Vista (BV, 2.8°N, 60.7°W, dip: 18°), a low latitude region in the Brazilian sector, which occurred far after the onset of a magnetic storm recovery phase. Such occurrences were observed during seven magnetic storms with available data for BV. Thus, the ionospheric behavior on days around the magnetic storm that occurred on January 20

Enceladus produces plumes of water vapor and ice particles whose gaseous H2O molecules dissociate into OH and O. The gas ejecta form a large toroidal planetary cloud colocated with and partially sourced by a similarly large torus of ice grain ejecta. Gas torus neutrals are ionized by charge exchange, solar UV, and electron impacts, producing the thermal water group ions, W+ (O+, OH+, H2O+, and H3O+)

The ionosphere is very active and complex due to photo‐ionization from the solar activity, while traditional empirical models can only give a rough description of the variations in the ionosphere. Nowadays, Global Ionosphere Maps (GIMs) derived from denser Global Navigation Satellite Systems (GNSS) world ‐tracking data provide excellent Total Electron Content (TEC) dataset for global ionospheric research

In order to study the acceleration of ions originating from the tenuous exosphere and surface of the Moon, we analyzed data from the ElectroStatic Analyzer (ESA) and Flux Gate Magnetometer (FGM) carried by the Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) spacecraft. Previous investigations have modeled the acceleration of lunar ions by the

In this study we examine the ability of protons of solar origin to access the near‐equatorial inner magnetosphere. Here we examine four distinct solar proton events from 20‐200 MeV, concurrent with both quiet‐time and storm‐time conditions using proton data from the ACE satellite in the solar wind upstream of Earth and data from the REPT instrument aboard Van Allen Probes. We examine the direct flux

Enceladus’ plume is the dominant source of neutrals and plasma in Saturn’s magnetosphere. The plasma results from the ionization of icy particles and water vapor, which are vented into Saturn’s inner magnetosphere through fissures in Enceladus’ southern polar region. These fissures are subjected to tidal stresses that can vary as Enceladus moves in a slightly eccentric orbit around Saturn. Plume activity

Upward‐moving energetic electrons with energies of 1 MeV and above were observed over the entire Jovian polar region. The electrons were found to be associated with intense broadband whistler‐mode waves, similar to terrestrial whistler‐mode auroral hiss. Upward‐propagating whistler‐mode hiss at Earth is known to be generated by upward‐moving, magnetic field‐aligned electron beams (from electric field‐aligned

Global Navigation Satellite System (GNSS) atmospheric radio occultation (RO) has been an active remote sensing method to explore the Earth’s atmosphere recently. The RO products especially atmospheric bending angles have been widely used for climate study. However, the residual ionospheric error (RIE) still exists to a certain extent after the widely‐used linear combination in bending angle calculation

Observational datasets in the polar middle atmosphere are extremely valuable for understanding the polar dynamics and coupling between lower and middle atmosphere. Using the long‐term datasets observed with an OH all‐sky imager, a Fabry‐Perot Interferometer at Resolute Bay observatory, Canada (74.7°N, 94.9°W), Microwave Limb Sounder and reanalysis data, we study the characteristics of small‐scale gravity

During a geomagnetic storm, the energy deposition from magnetosphere to thermosphere through Joule heating leads to variations in the total mass density of thermosphere. In this study, measurements obtained from the Challenging Minisatellite Payload and Gravity Recovery and Climate Experiment satellites between 2002 and 2008 are used to study the response of thermospheric density during geomagnetic

Ionospheric outflow is an important plasma source that feeds the near‐Earth magnetotail with heavy oxygen ions. Because these ions can significantly alter the structure and stability of the magnetotail current sheet, the characteristics of this outflow are important for accurate magnetosphere modelling, including modelling of substorms ‐‐ a key element of magnetosphere dynamics. Using Time History

The standard method for identifying rotational discontinuities in spacecraft data has been to examine how well the Walen relation is satisfied. In this paper, we apply two different versions of the Walen test to nearly 1000 dayside magnetopause crossings by the Magnetospheric Multi‐Scale spacecraft, with the objective of comparing their performance. The first approach is to evaluate the Walen relation

We ran the IRAP Plasmasphere Ionosphere Model (IPIM) for several flux tubes at different distances from Earth for very quiet conditions, in order to model the convection and corotation transport of closed flux tubes in the plasmasphere for tilted/eccentric dipolar magnetic field configuration and for solstice and equinox conditions. For each simulation, the model was run for 30 days in order to study

The Κ distribution function is fitted to the entire dataset of MESSENGER's 1‐minute Fast Imaging Plasma Spectrometer (FIPS [Andrews et al., 2007]) proton spectra, then artificial neural networks (ANNs) are used to assess the quality of this fit to the data. The Κ distribution function is fitted to each proton spectrum using the downhill‐simplex method, providing an estimate for density, n, temperature

Routine monitoring and forecasting of the ionosphere is becoming imperative for our society due to the rapid increase of our reliance on space‐based technologies. In the last two decades, satellite remote sensing of the OI 135.6‐nm airglow emission has been used as a primary means for inferring the nighttime ionosphere on a global scale. By contrast, the OI 130.4‐nm emission, another prominent airglow

Magnetosonic waves, with the frequency between proton cyclotron frequency and lower hybrid frequency, mainly occur near the Earth's magnetic equatorial plane and play an important role in the magnetospheric dynamics. In this paper, we report unusual magnetosonic waves with nonlinear harmonics observed by Magnetospheric Multiscale (MMS) mission in the magnetotail. These magnetosonic waves have multi‐band

Poleward moving auroral form (PMAF) is a type of dayside auroral pattern. The distinguishing characteristic of a PMAF is its separation from the auroral oval and subsequent poleward motion. It has been reported and widely accepted that PMAFs occur more frequently during periods with dominant southward Interplanetary Magnetic Field (IMF). However, most ground‐based optical observations were made near

ALTAIR radar data acquired during the NASA WINDY sounding rocket campaign on Kwajalein Atoll in late August and September, 2017, are analyzed to study the development of postsunset F ‐region ionospheric plasma density irregularities associated with equatorial spread F (ESF) conditions. Unstable conditions existed on nine of ten observing nights during the campaign. The first indication of instability

Gravity wave propagation from the troposphere into the thermosphere has often been modeled by assuming a complex vertical wavenumber m, with the imaginary part accounting for viscous and thermal dissipation. An alternative is to assume a complex wave frequency ω, which leads to a simpler form of the dispersion relation and different wave solutions described by complex‐ω ray theory. Here the solutions

Geomagnetic storms are one of the most energetic space weather phenomena. Previous studies have shown that the eigenfrequencies of closed magnetic field lines in the inner magnetosphere decrease during storm times. This change suggests either a reduction in the magnetic field strength and/or an increase in its plasma mass density distribution. We investigate the changes in local eigenfrequencies by

We discuss Wind observations of a long and slow magnetic cloud (MC) propagating through large‐amplitude Alfvén waves (LAAWs). The MC axis has a strong component along GSE X, as also confirmed by a Grad‐Shafranov reconstruction. It is overtaking the solar wind at a speed roughly equal to the upstream Alfvén speed, leading to a weak shock wave 17 hrs ahead. We give evidence to show that the nominal sheath

Using energetic ion composition data at the dayside magnetopause measured by Magnetospheric Multiscale (MMS) satellites, we study the responses of H+, O+ density (1‐40 keV) and their ratio to geomagnetic activity and solar wind conditions, their spatial distributions in the XYGSM plane for different ranges of the above parameters are presented as well. The dependencies of the H+ and O+ fluxes spatial

Recent work has demonstrated that global Pc5 pulsations observed by ground‐based magnetometers may be accompanied by periodic oscillations in the total electron content (TEC) of the ionosphere measured by GPS receivers. These TEC observations may provide new insights into magnetosphere‐ionosphere coupling mechanisms, especially when combined with other ground‐based observational techniques. Presented

White‐light images from Heliospheric Imager‐1 (HI1) onboard the Solar Terrestrial Relations Observatory (STEREO) provide 2‐dimensional (2D) global views of solar wind transients traveling in the inner heliosphere from two perspectives. How to retrieve the hidden three‐dimensional (3D) features of the transients from these 2D images is intriguing but challenging. In our previous work (Li et al., 2018)

A paper by Jiang et al. (2019) apparently tries to find common ground between observations of the F3 layer and TIDs by referring to the later when observed near the equatorial anomaly peak as a new type 1 and TIDs by using ray‐tracing models with arbitrarily adjusted TID parameters. Further confusion in conflating the two separate phenomena is created by referring to both as “stratification”. This

This paper is a response to the comment by Lynn et al. (2019) on the paper by Jiang et al. (2019a). Although we disagree with Lynn et al. (2019), nevertheless, we do thank them for their comments, since they have given us the opportunity to revisit and clarify some points. In Jiang et al. (2019a) and this reply, we found that the F2 layer stratification induced by gravity waves/TIDs can last for about

Whistler mode waves observed in the Earth's inner magnetosphere at frequencies between about 0.5 and 4 kHz which exhibit a nearly periodic time modulation of the wave intensity are called quasiperiodic (QP) emissions. Conjugate measurements of QP events at several different locations can be used to estimate their spatial extent and spatio‐temporal variability. Results obtained using conjugate QP measurements

This paper describes insights into the nature of co‐rotating plasmaspheric irregularities (CPIs) enabled by a newly developed method for range‐ and time‐resolved tomographic images of these structures. This was originally developed using high‐precision measurements of total electron content (TEC) gradients toward cosmic radio sources using an interferometric radio telescope, the Very Large Array (VLA)

Magnetic fluctuations in the near‐Earth magnetotail are an important signature of substorm onset. In a previous statistical study, we reported their occurrence rates, spatial distributions, and relationship with plasma flows. In the present study, we investigated their spectral properties using 11 years of zmeasurements from the Time History of Events and Macroscale Interactions during Substorms mission

With the successful launch of the satellite mission Gravity Recovery and Climate Experiment (GRACE) Follow‐On in May 2018 the opportunity arises to resume the analysis of accelerometer data regarding space weather induced perturbations of the Earth's thermosphere. On 21 August 2018 a complex interplanetary coronal mass ejections occurred on the Sun, which subsequently triggered an unexpected large

The Global‐scale Observations of the Limb and Disk (GOLD) is a National Aeronautics and Space Administration mission of opportunity designed to study how the Earth's ionosphere‐thermosphere system responds to geomagnetic storms, solar radiation, and upward propagating atmospheric tides and waves. GOLD employs two identical ultraviolet spectrographs that make observations of the Earth's thermosphere

The Global‐scale Observations of the Limb and Disk (GOLD) is a National Aeronautics and Space Administration mission of opportunity designed to study how the Earth's ionosphere‐thermosphere system responds to geomagnetic storms, solar radiation, and upward propagating atmospheric tides and waves. GOLD employs an instrument with two identical ultraviolet spectrographs that make observations of the Earth's

In the magnetosheath, intense whistler mode waves, called “Lion roars,” are often detected in troughs of magnetic field intensity in mirror mode structures. Using data obtained by the four Magnetospheric Multiscale (MMS) spacecraft, we show that reversals of gradient of magnetic field intensity along the magnetic field correspond to reversals of the field‐aligned component of Poynting flux of whistler

The Van Allen radiation belts in the magnetosphere have been extensively studied using models based on radial diffusion theory, which is derived from a quasi‐linear approach with prescribed inner and outer boundary conditions. The 1D diffusion model requires the knowledge of a diffusion coefficient and an electron loss timescale, which is typically parameterized in terms of various quantities such

The Martian ionopause boundary detected as steep gradients in the local electron density profiles from the Mars Advanced Radar for Subsurface and Ionospheric Sounder on Mars Express is studied individually and statistically and compared to the photoelectron boundary identified by the drop of photoelectron signature due to CO2 and O molecules. In ~90% of the cases where we have electron energy flux

A primary limitation for accurate specification and forecasting of the Thermosphere‐Ionosphere (TI) system is uncertainty in the system forcing. This significantly impacts users who have operational and real‐time interests in the current and future state of the TI system. Since GOLD observations are expected to provide information about both the current state and forcing of the TI system, GOLD products

The spatial and temporal characterization of trapped charged particle trajectories in magnetospheres has been extensively studied in dipole magnetic field structures. Such studies have allowed the calculation of spatial quantities, such as equatorial loss cone size as a function of radial distance; the location of the mirror points along particular field lines (L‐shells) as a function of the particle's

Near‐epicentral mesopause airglow perturbations, driven by infrasonic acoustic waves (AWs) during a night‐time analog of the 2011 M9.1 Tohoku‐oki earthquake, are simulated through the direct numerical computation of the 3D nonlinear Navier‐Stokes equations. Surface dynamics from a forward seismic wave propagation simulation, initialized with a kinematic slip model and performed with the SPECFEM3D_GLOBE

Pulsating auroras (PsAs) are low‐intensity diffuse aurora, which switch on and off with a quasi‐periodic oscillation period from a few seconds to ~ 10 s. They are predominantly observed after magnetic midnight, during the recovery phase of substorms and at the equatorward boundary of the auroral oval. PsAs are caused by precipitating energetic electrons, which span a wide range of energies between

A special summer mid‐day population of echoes has been reported by HF radars at ranges less than 300 km. These echoes come from a narrow altitude region near 100 km. Their spectral width indicates that they decay at a rate controlled by ambipolar diffusion. We label the echo regions as 'Far‐aspect Angle Irregularity Regions' (FAIR) by contrast with 'High‐aspect Angle Irregularity Regions' (HAIR) documented

We study quasiperiodic very low frequency (VLF) emissions observed simultaneously by Van Allen Probes spacecraft and Kannuslehto and Lovozero ground‐based stations on 25 December 2015. Both Van Allen Probes A and B detected quasiperiodic emissions, probably originated from a common source, and observed on the ground. In order to locate possible regions of wave generation, we analyze wave‐normal angles

To find the best method of predicting when daily relativistic electron flux (>2 MeV) will rise at geosynchronous orbit, we compare model predictive success rates (true positive rate or TPR) for multiple regression, ARMAX, logistic regression, a feed‐forward multilayer perceptron (MLP), and a recurrent neural network (RNN) model. We use only those days on which flux could rise, removing days when flux

Understanding the dynamic evolution of relativistic electrons in the Earth's radiation belts during both storm and nonstorm times is a challenging task. The U.S. National Science Foundation's Geospace Environment Modeling (GEM) focus group “Quantitative Assessment of Radiation Belt Modeling” has selected two storm time and two nonstorm time events that occurred during the second year of the Van Allen

NASA's Parker Solar Probe (PSP) mission is currently investigating the local plasma environment of the inner heliosphere (<0.25 R⊙) using both in situ and remote sensing instrumentation. Connecting signatures of microphysical particle heating and acceleration processes to macroscale heliospheric structure requires sensitive measurements of electromagnetic fields over a large range of physical scales

The prebreakup arc at the inner edge of the auroral boundary is intensified upon arrival of an auroral streamer—the ionospheric signature of the earthbound mesoscale plasma flows (MPF). Yet the cause of electron precipitation enhancement only in this region remains unclear. We suggest that the intensified precipitation comes from the turbulent plasmasphere boundary layer (TPBL) that forms due to short

Forecasting relativistic electron fluxes at geostationary Earth orbit (GEO) has been a long‐term goal of the scientific community, and significant advances have been made in the past, but the relation to the interior of the radiation belts, that is, to lower L‐shells, is still not clear. In this work we have identified 60 relativistic electron enhancement events at GEO to study the radial response