Using the location of equatorial ionization anomaly (EIA) crest derived from GPS observations and CHAllenging Minisatellite Payload (CHAMP) satellite measurement, along with the F2 layer peak height (hmF2), critical frequency (foF2) and the equatorial electrojet (EEJ) in India and China longitudinal sectors, we found the obvious 6‐day oscillation in these ionospheric parameters during 16 April to 31

The paper summarizes the properties of precipitation of magnetospheric electrons with energy above several hundred keV recorded by observing X‐ray bremsstrahlung in the polar stratosphere above the Murmansk region, Russia, in 1961‐2019. Precipitation occurrence rate demonstrates a clear dependence on the solar activity with a maximum at the decay phase of the 11‐year solar cycle, similarly to the variability

Assessing the statistical significance of electromagnetic anomalies in the ultralow frequency (ULF) range observed prior to earthquakes is a necessary step toward determining whether these perturbations constitute actual earthquake precursors. A statistical epoch analysis (SEA) was recently performed by Han et al. (2014, https://doi.org/10.1002/2014JA019789) to analyze earthquakes happening between

Ion upflow in the F region and topside ionosphere can greatly influence the ion density and fluxes at higher altitudes and thus has significant impact on ion outflow. We investigated the statistical characteristics of ion upflow and downflow using a 3‐year (2011–2013) data set from the Poker Flat Incoherent Scatter Radar (PFISR). Ion upflow is twice more likely to occur on the nightside than on the

Ultra‐low‐frequency (ULF, 0.001–1 Hz) perturbations are important aspect of the dynamics in the inner magnetosphere: They are responsible for radial transport (diffusion) of high‐energy electrons and for energizing the ionosphere with field‐aligned currents. This study is devoted to properties of ULF perturbations generated at the magnetopause, their propagation into the inner magnetosphere, and their

This work conducts a statistical study of the subauroral polarization stream (SAPS) feature in the North American sector using Millstone Hill incoherent scatter radar measurements from 1979 to 2019, which provides a comprehensive SAPS climatology using a significantly larger database of radar observations than was used in seminal earlier works. Key features of SAPS and associated electron density (Ne)

Type‐A (weaker and wider Doppler spectra) and Type‐B (stronger and narrower Doppler spectra) echoes are inherent to the puzzling 150‐km echoing phenomenon. In this paper, we investigate the characteristics and possible origin of the Type‐A and Type‐B 150‐km echoes using high‐resolution 53‐MHz radar and Digisonde observations from Gadanki. Results show that the Type‐A echoes dominate the echoing phenomenon

Using the full relativistic test particle (TP) simulation code, we investigate the parametric dependence of electron scattering and phase space density evolution driven by magnetosonic (MS) waves at L = 4.5 both inside and outside the plasmapause. The scattering effects caused by Landau resonance, bounce resonance, and the transit‐time effect are all involved in the study. The net scattering effects

The effects of solar flares on the upper atmosphere of Mars are large but poorly constrained by observations. These effects are an important aspect of the response of Mars to space weather events and may also influence the escape of volatiles from Mars, particularly in the solar system's early history. Here we report the effects of the X8.2 flare on 10 September 2017 on the density and composition

Two‐dimensional hybrid particle‐in‐cell (PIC) simulations are carried out on a constant L‐shell (or drift shell) surface of the dipole magnetic field to investigate the generation process of near‐equatorial fast magnetosonic waves (a.k.a equatorial noise; MSWs hereafter) in the inner magnetosphere. The simulation domain on a constant L‐shell surface adopted here allows wave propagation and growth in

The formation of polar cap density enhancements, such as tongues‐of‐ionization (TOIs), are often attributed to enhanced dayside reconnection and convection due to solar wind changes. However, ionospheric poleward moving density enhancements can also form in the absence of changes in the solar wind. This study examines how TOI and patch events that are not triggered by solar wind changes relate to magnetospheric

Superthermal electron precipitation is one of the main sources supporting the Mars nightside ionosphere. It is expected that solar wind electron fluxes are to increase significantly during interplanetary coronal mass ejections (ICMEs) and therefore an enhanced nightside ionospheric density. This study is to quantify the variation of the precipitating and deposited electron fluxes during five extreme

We propose a mechanism for the formation of the horse‐collar auroral configuration during periods of strongly northward interplanetary magnetic field (IMF), invoking the action of dual‐lobe reconnection (DLR). Auroral observations are provided by the Imager for Magnetopause‐to‐Aurora Global Exploration (IMAGE) satellite and spacecraft of the Defense Meteorological Satellite Program (DMSP). We also

Space‐borne Langmuir probes generally have a self‐wake behind themselves due to supersonic relative velocities (Mach number M > 1) between the spacecraft and ambient plasma ions. Such a wake may create difficulties for correctly measuring plasma characteristics. Here we present a new technique—the Double Hemispherical Probe (DHP) to characterize and minimize the self‐wake effects on probe measurements

We present a statistical investigation of the seasonal effect on hemispheric asymmetry in the auroral currents during low (Kp < 2) and high (Kp ≥ 2) geomagnetic activity. Five years of magnetic data from the Swarm satellites has been analyzed by applying the spherical elementary current system (SECS) method. Bootstrap resampling has been used to remove the seasonal differences between the hemispheres

Several interplanetary spacecraft have inferred the presence of nanometer‐sized dust grains in the inner heliosphere accelerated to near‐solar wind velocities based on observations by radio wave antennas. These “nanodust” grains exhibit unique behavior in interplanetary space as they are strongly affected by both the solar gravitational force and the electromagnetic Lorentz force from the convecting

The solar wind plasma is a major plasma source for the Earth's magnetosphere, which has a strong influence on the magnetotail plasma and field properties. The relative importance of different plasma entry mechanisms and pathways is largely determined by the solar wind conditions. Therefore, the spatial and temporal dependence of magnetotail plasma and field properties under different kinds of solar

Recent work by Oberhagemann and Mann (2020, https://doi.org/10.1029/2019GL085271) has shown that ballooning instabilities in the transition region between dipolar and taillike fields associated with substorm onset may be triggered by an anisotropic pressure distribution that moves from an initially mild perpendicular anisotropy toward more parallel anisotropy. Here we examine the mechanism which can

The terrestrial magnetosphere is perpetually exposed to and significantly deformed by the interplanetary magnetic field (IMF) in the solar wind. This deformation is typically detected at discrete locations by space‐ and ground‐based observations. Earth's aurora, on the other hand, is a globally distributed phenomenon that may be used to elucidate magnetospheric deformations caused by IMF variations

From the analysis of Digisonde data over Brazilian equatorial and low‐latitude sites, we investigate the relative importance of the different parameters driving the generation of rising bubble‐type and bottom‐type spread F (SF) irregularities. Data for the complete month of October 2001, a solar maximum epoch (F10.7 = 210), and that of October 2008, an extended solar minimum period (F10.7 = 70), are

A clear understanding of storm‐time magnetospheric dynamics is essential for a reliable storm forecasting capability. The dayside magnetospheric response to an interplanetary coronal mass ejection (ICME; dynamic pressure Pdyn > 20 nPa and storm‐time index SYM‐H < −150 nT) is investigated using in situ OMNI, Geotail, Cluster, MMS, GOES, Van Allen Probes, and THEMIS measurements. The dayside magnetic

The gravity‐driven and pressure‐gradient currents coexist in the ionosphere, and their effects are significant in there, rather than at the outside of the ionosphere; and can be important while studying the ionospheric currents using low‐Earth‐orbiting (LEO) satellite measurements. Maute and Richmond (2017, https://doi.org/10.1002/2017JA024841) (MR17) have demonstrated that above the F region peak

An algorithm to detect high‐speed ionospheric flow channels (FCs) in the polar cap was applied to data from the Longyearbyen radar of the Super Dual Auroral Radar Network. The Longyearbyen radar is at high‐latitude (78.2°N, 16.0°E geographic coordinates) and points North‐East, therefore is in an ideal position for measuring zonal flows in the polar cap. The algorithm detected 998 events in the dayside

We present a novel algorithm that predicts the probability that the time derivative of the horizontal component of the ground magnetic field dB/dt exceeds a specified threshold at a given location. This quantity provides important information that is physically relevant to Geomagnetically Induced Currents (GIC), which are electric currents {associated with} sudden changes in the Earth's magnetic field

One of the main sources of magnetospheric particles is solar wind penetration through the magnetopause ‐ a current sheet separating the cold, dense magnetosheath from the hot, rarified magnetospheric plasmas. The mechanism responsible for magnetosheath particle transport across the magnetopause has been better investigated for the near‐Earth day‐side magnetopause (contrary to the night side), where

This paper studies the ionosphere's response to the annular solar eclipse on 26 December 2019, utilizing the following ground‐based and space‐borne measurements: Global Navigation Satellite System (GNSS) total electron content (TEC) data, spectral radiance data from the Sentinel‐5P satellite, in situ electron density and/or temperature measurements from DMSP and Swarm satellites, and local magnetometer

Using Magnetospheric Multiscale (MMS) data, we find, classify and analyze transient dynamic pressure enhancements in the magnetosheath (jets) from May 2015 to May 2019. A classification algorithm is presented, using in‐situ MMS data to classify jets (N = 8499) into different categories according to their associated angle between IMF and the bow shock normal vector (θBn). Jets appearing for θBn <45

The local generation of high‐frequency plasmaspheric hiss has recently been reported by a case study (He et al., 2019). In this research, we perform statistics of global distributions of the locally generated high‐frequency plasmaspheric hiss (LHFPH) for different levels of substorm activity, using 6‐year observational data from Van Allen Probes. The statistics find that the LHFPH amplitude presents

The most remarkable feature of the ultraviolet auroras at Jupiter is the ever‐present and almost continuous curtain of bright emissions centered on each magnetic pole and called the main emissions. According to the widely‐accepted theory, it results from an electric current loop transferring momentum from the Jovian ionosphere to the magnetospheric plasma. However, predictions based on this theory

In this paper, we address the issue of interchange instability excitation criterion in the magnetospheric plasma in the presence of the velocity shear using a magnetohydrodynamic approach. We conducted our analysis for the arbitrary β plasma configuration using a WKB approximation for wavelengths, λ, much smaller than the characteristic plasma inhomogeneity scale, L, and found two branches of waves

In this study, we utilized both ground‐based and space‐borne observations including total electron content (TEC) from Beidou geostationary satellites, two‐dimensional TEC maps from the worldwide dense Global Navigation Satellite System receivers, ionosondes, and in situ electron density (Ne) and electron temperature (Te) from both Swarm and China Seismo‐Electromagnetic Satellite satellites, to investigate

We have developed the automatic detection scheme for upper hybrid resonance (UHR) frequency using a convolutional neural network (CNN) from the electric field spectra obtained by the plasma wave experiment (PWE) aboard Arase. In this paper, we investigate the practical capability of this scheme in terms of actual scientific use case. We find that the average error rate is below 7.8% when the wave frequency

We report on the dynamics of field‐aligned currents (FACs), broadband geomagnetic pulsations, and airglow obtained from the Irkutsk (IRK), Mondy (MND), and Borok (BOX) midlatitude geomagnetic observatories and the Tory (TOR) optical observatory during storm substorms. For the first time, using the short duration, Δt < 0.5 min, high‐frequency component of the burst pulsations (Pi1B), we determined the

We investigated the excitation mechanism and global distribution of internally driven Pc3‐Pc5 ULF waves in the inner magnetosphere using a kinetic and self‐consistent simulation (GEMSIS‐RC model). These waves can be excited through the drift‐bounce resonance with ring current ions injected into the inner magnetosphere during substorms. Initial phase space density of ring current ions is the butterfly

Whistler mode chorus waves have recently been established as the most likely candidate for scattering relativistic electrons to produce the electron microbursts observed by low altitude satellites and balloons. These waves would have to propagate from the equatorial source region to significantly higher magnetic latitude in order to scatter electrons of these relativistic energies. This theoretically

Auroral particle precipitation is the main source of ionization on the nightside, making it a critical factor in geospace physics. This magnetosphere‐ionosphere linkage directly contributes to, even controls, the nonlinear feedback within this coupled system. One study has dominated our understanding of this connection, presenting a pair of equations relating auroral particle precipitation to ionospheric

On 12 November 2015 the Magnetospheric Multiscale (MMS) spacecraft traversed the magnetopause from the magnetosphere to the magnetosheath encountering evidence of magnetic reconnection and a tiny flux transfer event (FTE) on the magnetosheath side of the magnetopause boundary layer. The FTE exhibited a large negative‐positive bipolar variation in the normal magnetic field component (BN), an enhanced

In this paper, we have evaluated the role of interplanetary magnetic field (IMF) By on the asymmetry of the ring current during the main phase of geomagnetic storms. The mean H variations have been calculated using 31 ground magnetic stations over magnetic latitudes of 09–45° following the methodology of Li et al. (2011, https://doi.org/10.1029/2011JA016886). Further, the magnetic local time (MLT)

Based on observations of Van Allen Probe‐A during the period from 19 September 2012 to 28 February 2016, the relations of the fast magnetosonic (MS) wave amplitude Bw with kp index, the wave normal angle (WNA) and the wave normalized frequency (norF) are presented, respectively. Then, we establish an analytical regression model for MS wave amplitude as a function of geomagnetic storm activity (presented

No abstract is available for this article.

Three lower‐band (f < 0.5 fce) chorus riser elements detected in the dayside generation region were studied in detail using the Van Allen Probe data. Two subelements/wave packets within each riser were examined for their wave “frequency” constancy within seven consecutive wave cycles. The seven wave cycles contained the maximum amplitudes of the subelements/packets. Maximum variance B1 zero crossings

We present a novel technique to analyze VDF, which allows to capture their fine structure including wave‐particles resonances. By applying the technique to magnetospheric multiscale (MMS) data, the simultaneous observation of characteristic three‐dimensional (3‐D) signatures in the electron velocity distribution function (VDF) and intense quasi‐monochromatic waves in the terrestrial magnetosheath is

Results from a study of automatic aurora classification using machine learning techniques are presented. The aurora is the manifestation of physical phenomena in the ionosphere‐magnetosphere environment. Automatic classification of millions of auroral images from the Arctic and Antarctic is therefore an attractive tool for developing auroral statistics and for supporting scientists to study auroral

Electron pitch angle distributions (PADs) are very important to understand dynamics in the Earth's magnetosphere. Using observations of the Magnetospheric Multiscale (MMS) mission, we statistically investigate the characteristics of several types of electron PADs with energies of 200 eV to 2 keV (low energy) and 2–30 keV (energetic energy) inside the dayside magnetopause (L = 8 ∼ 13). For the low (energetic)

A two‐band plasmaspheric hiss consisting of a low‐frequency band (normal hiss with the frequency below 2 kHz) and a high‐frequency band (locally generated hiss with the frequency up to 10 kHz) was observed on 6 January 2014 by the Van Allen Probes (He et al., 2019, https://doi.org/10.1029/2018GL081578). The electron scattering effect driven by this kind of two‐band plasmaspheric hiss is evaluated by

The morphology of the auroral oval is an important geophysical parameter that helps to further understand the solar wind‐magnetosphere‐ionosphere coupling process. However, it is still a challenging task to automatically obtain auroral poleward and equatorward boundaries completely and accurately. In this paper, a new model based on the deep feature and dual level set method is proposed to extract

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft regularly observed the magnetospheric flanks of Mercury during its orbital phase. Data from the Magnetometer (MAG) and the Fast Imaging Plasma Spectrometer (FIPS) allow us to investigate the statistical properties of planetary ions (Na+) in the presence of Kelvin‐Helmholtz (KH) waves at the duskside magnetopause

Various subauroral optical features have been studied by analyzing data collected during periods of geomagnetic disturbances. Most events have been typically found at geomagnetic latitudes of 45–60°. In this study, however, we present a red arc event found at geomagnetic 68° north (L ≈ 7.1) in the Scandinavian sector during a period of geomagnetically quiet conditions within a short intermission between

This paper characterizes the impacts of sudden stratospheric warmings (SSWs) and mesospheric coolings (MCs) on the light species distribution (i.e., helium [He], and atomic hydrogen [H]) of the thermosphere using a combined data‐modeling approach. Performing a set of numerical experiments with a general circulation model whose middle atmospheric dynamical and thermodynamical fields were constrained

Utilizing Magnetospheric Multiscale (MMS) observation in the tail plasma sheet, we study the vorticity field (ω = ∇ × V) of the plasma bulk (convective) velocity within the bursty bulk flow (BBF) in detailed. Two typical events are presented. In the event on 25 June 2017, Ey is the main component. In the other event on 6 July 2017, Ez is the main component. For both cases, the BBF electric field is

Past studies have demonstrated that the interplanetary magnetic field (IMF) By component introduces asymmetries in the magnetosphere‐ionosphere (M‐I) system, though the exact timings involved are still unclear with two distinct mechanisms proposed. In this study, we statistically analyze convective flows from three regions of the M‐I system: the magnetospheric lobes, the plasma sheet, and the ionosphere

Understanding the day‐to‐day variability of equatorial plasma bubble (EPB) irregularities has been a major challenge for many decades that makes the deterministic prediction of EPBs remain elusive. In the present study, we report a case of intense and periodic EPBs observed during 8 and 9 April 2013 by the 47‐MHz Equatorial Atmosphere Radar at Kototabang, Indonesia. The periodic EPBs separated by about

Based on the Mars Atmosphere and Volatile EvolutioN (MAVEN) observations, we have analyzed the role of the crustal magnetic field on ion loss driven by the direct interaction of the solar wind with the Mars ionosphere. Crustal magnetic fields significantly attenuate the ion ionospheric motions and raise the flux of returning ions. On the other hand, since the ion densities in the ionosphere with strong

We present observations from five Mars Express (MEX) orbits in September 2016 while the spacecraft passed through the Martian induced magnetotail at altitudes up to 3,500 km. On these orbits, the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument was operated in Active Ionospheric Sounding (AIS) mode at much higher altitude than normal, acting as a local sounder and detecting

We present a method of characterizing the horizontal and vertical electron density roughness of the D‐region ionosphere using Nationwide Differential Global Position System (NDGPS) transmitters as low‐frequency (LF; 30–300 kHz) and medium‐frequency (MF; 300–3,000 kHz) signals of opportunity. The horizontal roughness is characterized using an amplitude cross‐correlation method, which yields the correlation

On 31 January 2016, the flux of >2 MeV electrons observed by Geostationary Operational Environmental Satellite (GOES)‐13 dropped to the background level during a minor storm main phase (−48 nT). Then, a second storm (−53 nT) occurred on 2 February; during the 3 days after its main phase, the flux remained at background level. Using data from various instruments on the GOES, Polar Operational Environmental

The FORMOSAT‐7/COSMIC‐2 (F7/C2) satellite mission was launched on 25 June 2019 with six low‐Earth‐orbit satellites and can provide thousands of daily radio occultation (RO) soundings in the low‐latitude and midlatitude regions. This study shows the preliminary results of space weather data products based on F7/C2 RO sounding: global ionospheric specification (GIS) electron density and Ne‐aided Abel

Measurements in the heliosphere and high‐resolution fluid simulations give clear indications for the anisotropy of plasma turbulence in the presence of magnetic fields. How this anisotropy affects transport processes like diffusion and dispersion remains an open question. The first efforts to characterize Lagrangian single‐particle diffusion and two‐particle dispersion in incompressible magnetohydrodynamic

This study presents simulations of the coupled space environment during a geomagnetic storm that separates the different sources of near‐Earth plasma. These simulations include separate fluids for solar wind and ionospheric protons, ionospheric oxygen, and the plasmasphere. Additionally, they include the effects of both a hot ring current population and a cold plasmaspheric population simultaneously

The three‐dimensional computerized ionospheric tomography (3DCIT) technique is used to reconstruct the spatial distribution of storm enhanced density (SED) based on the global positioning system (GPS) total electron content (TEC) measurements over the North American area during the March 17, 2013 storm. The reconstruction results are carefully validated with observations from three ionosonde stations