Long-term variations in the relativistic (∼MeV) electrons in the Earth's radiation belt are explored to study seasonal features of the electrons. An L-shell dependence of the seasonal variations in the electrons is reported for the first time. A clear ∼6 month periodicity, representing one/two peaks per year, is identified for 1.5–6.0 MeV electron fluxes in the L shells between ∼3.0 and ∼5.0. The relativistic

Abstract. The foreshock located upstream of Earth's bow shock hosts a wide variety of phenomena related to the reflection of solar wind particles from the bow shock and the subsequent formation of ultra-low frequency (ULF) waves. In this work, we investigate foreshock cavitons, which are transient structures resulting from the non-linear evolution of ULF waves, and spontaneous hot flow anomalies (SHFAs)

Using data on the proton fluxes of the Earth's radiation belts (ERBs) with energy ranging from 0.2 to 100 MeV on the drift L shells ranging from 1 to 8, the quasi-stationary distributions over the drift frequency fd of protons around the Earth are constructed. For this purpose, direct measurements of proton fluxes of the ERBs during the period from 1961 to 2017 near the geomagnetic equator were employed

Identification of a large-amplitude Alfvén wave decaying into a pair of ion-acoustic and daughter Alfvén waves is one of the major goals in the observational studies of space plasma nonlinearity. In this study, the decay instability is analytically evaluated in the 2-D wavenumber domain spanning the parallel and perpendicular directions to the mean magnetic field. The growth-rate determination of the

Abstract. When wireless electromagnetic waves pass through the earth's atmosphere, they are affected by ionospheric irregularities, and their amplitude and phase will jitter rapidly in a short period of time, which is called ionospheric scintillation. With the human exploration of outer space and the demand for space communication, the study of ionospheric scintillation characteristics and its influence

Abstract. The historical magnetic observatory Clementinum operated in Prague from 1839 to 1926. The data from the yearbooks that recorded the observations at Clementinum have recently been digitized and were subsequently converted in this work into the physical units of the International System of Units (SI). Introducing a database of geomagnetic data from this historical source is a part of our paper

The variability in the amplitudes of the lunar semidiurnal tide was investigated using maps of total electron content over Brazil from January 2011 to December 2014. Long-period variability showed that the annual variation is always present in all investigated magnetic latitudes, and it represents the main component of the temporal variability. Semiannual and triannual (two and three times a year,

Abstract. In this work we show the result of the numerical simulation of the gravity waves (GWs) D region disturbance. Effectively, using the Glukhov-Pasko-Inan (GPI) model of the electron density in the D region we were figured out the response of the electron density due to gravity wave neutral atmosphere oscillation. As a consequence to the D region disturbance, the electron density sometimes increases

Abstract. We tackle the Io's aurora source and topology by carrying out a set of global hybrid simulations of Io's interaction with the plasma torus under different model geometry and background conditions. Based on the simulated results, we compute the photon emission rates above the Io's surface and present the resulting images from a virtual telescope and topological maps showing the distribution

A total of 10 radars from the Super Dual Auroral Radar Network (SuperDARN) in Antarctica were used to estimate the spatial area over which energetic electron precipitation (EEP) impacts the D-region ionosphere during pulsating aurora (PsA) events. We use an all-sky camera (ASC) located at Syowa Station to confirm the presence of optical PsAs, and then we use the SuperDARN radars to detect high frequency

Abstract. Simulations of the ionospheric response to solar flux changes driven by the twenty-seven days solar rotation have been performed using the global 3-D Coupled Thermosphere/Ionosphere Plasmasphere electrodynamics (CTIPe) physics- based numerical model. Using the F10.7 index as a proxy for solar EUV variations in the model, the ionospheric delay at the solar rotation period is well reproduced

Abstract. In 2003, a decreasing trend has been reported in the long-term (1962–2001) fair weather atmospheric electric potential gradient (PG) measured in the Széchenyi István Geophysical Observatory (NCK, 47°38' N, 16°43' E), Hungary, Central Europe. The origin of this reduction has been the subject of a long-standing debate, due to a group of trees near the measurement site which reached significant

Abstract. We report an attenuation of hiss wave intensity in the duskside of outer plasmasphere in response to enhanced convection and substorm based on Van Allen Probes observations. Using test particle codes, we simulate the dynamics of energetic electron fluxes based on a realistic magnetospheric electric field model driven by solar wind and subauroral polarization stream. We suggest that the enhanced

A new incoherent scatter radar called EISCAT 3D is being constructed in northern Scandinavia. It will have the capability to produce volumetric images of ionospheric plasma parameters using aperture synthesis radar imaging. This study uses the current design of EISCAT 3D to explore the theoretical radar imaging performance when imaging electron density in the E region and compares numerical techniques

Abstract. We present results of noon–midnight meridional plane global hybrid-Vlasov simulations of the magnetotail ion dynamics under steady southward interplanetary magnetic field using the Vlasiator model. The simulation results show magnetotail reconnection and formation of earthward and tailward fast plasma outflows. The hybrid-Vlasov approach allows us to study ion velocity distribution functions

Abstract. The Mesosphere and Lower Thermosphere (MLT) is a critical region that must be accurately reproduced in General Circulation Models (GCMs) that aim to include the coupling between the lower & middle atmosphere and the thermosphere. An accurate representation of the MLT is important for improved climate modelling and the development of a whole atmosphere model. This is because the atmospheric

Coincident auroral far-ultraviolet (FUV) and ground-based ionosonde observations are compared for the purpose of determining whether auroral FUV remote sensing algorithms that assume pure electron precipitation are biased in the presence of proton precipitation. Auroral particle transport and optical emission models, such as the Boltzmann 3-Constituent (B3C) model, predict that maximum E region electron

Modern investigations of dynamical space plasma systems such as magnetically complicated topologies within the Earth's magnetosphere make great use of supercomputer models as well as spacecraft observations. Space plasma simulations can be used to investigate energy transfer, acceleration, and plasma flows on both global and local scales. Simulation of global magnetospheric dynamics requires spatial

Abstract. In October 2017, the Scientific Committee on Solar-Terrestrial Physics (SCOSTEP) Bureau established a committee for the design of SCOSTEP's Next Scientific Program (NSP). The NSP committee members and authors of this paper, decided from the very beginning of their deliberations that the predictability of the Sun-Earth System from a few hours to centuries is a timely scientific topic, combining

Abstract. Geomagnetic storms are one of the space weather events. The radio signals transmitted by modern navigation systems suffer from the effects of storms which can degrade the performance of the whole system. In this study, the performance of BeiDou Navigation Satellite System (BDS) B1 frequency standard point positioning in China and its surrounding area during different classes of storms is

A set of 24 isolated, 46 compound, and 36 multi-night substorm events from the years 2008–2013 have been analysed in this study. Isolated substorm events are defined as single expansion–recovery phase pairs, compound substorms consist of multiple phase pairs, and multi-night substorm events refer to recurring substorm activity on consecutive nights. Approximately 200 nights of substorm activity observed

Abstract. The comparative research of the influence of different types of auroral particle precipitation and polar cap patches (PCP) on the GPS signals disturbances in the polar ionosphere was done. For this purpose, we use the GPS scintillation receivers at Ny-Ålesund and Skibotn, operated by the University of Oslo. The presence of the auroral particle precipitation and polar cap patches was determined

Ion acoustic waves were observed between 15 and 30 km from the centre of comet 67P/Churyumov–Gerasimenko by the Rosetta spacecraft during its close flyby on 28 March 2015. There are two electron populations: one cold at kBTe≈0.2 eV and one warm at kBTe≈2 eV. The ions are dominated by a cold (a few hundredths of electronvolt) distribution of water group ions with a bulk speed of (3–3.7) km s−1. A warm

Abstract. RBSPA observations suggest that the inner radiation belt high energy proton fluxes drop significantly during the storm main phase and recover in parallel to as the SYM-H index [Xu et al., 2019]. A natural problem arises: are these storm‐time proton flux variations in response to the magnetic field modifications adiabatic? Based on Liouville's theorem and conservation of the first and third

We have used empirical models for electric potentials and the magnetic fields both in space and on the ground to obtain maps of the height-integrated Pedersen and Hall ionospheric conductivities at high latitudes. This calculation required use of both “curl-free” and “divergence-free” components of the ionospheric currents, with the former obtained from magnetic fields that are used in a model of the

Abstract. Kelvin-Helmholtz billows (KHB) have been investigated in the Atmospheric Boundary layer (ABL) using Mono-static SODAR (Sound Detection And Ranging) designed and developed by CSIR-National Physical Laboratory, New Delhi over the capital region Delhi of India. KH billows are a primary cause of mixing in stably stratified conditions and hence have been studied widely by researchers by using

Abstract. The nature of the semi-annual variation in the relativistic electron fluxes in the Earth’s outer radiation belt is investigated using Van Allen Probes (MagEIS and REPT) and GOES (EPS) data during solar cycle 24. We perform wavelet and cross-wavelet analysis in a broad energy and spatial range of electron fluxes and examine their phase relationship with the axial, equinoctial and Russell-McPherron

Abstract. The magnetosheath is defined as the plasma region between the bow shock, where the super-magnetosonic solar wind plasma is decelerated and heated, and the outer boundary of the intrinsic planetary magnetic field, the so called magnetopause. Based on the Soucek-Escoubet magnetosheath flow model at Earth, we present the first analytical magnetosheath plasma flow model for Mercury. It can be

In this study we explore the seasonal variability of the mean winds and diurnal and semidiurnal tidal amplitude and phases, as well as the Reynolds stress components during 2019, utilizing meteor radars at six Southern Hemisphere locations ranging from midlatitudes to polar latitudes. These include Tierra del Fuego, King Edward Point on South Georgia island, King Sejong Station, Rothera, Davis, and

Abstract. Fragmented Aurora-like Emissions (FAEs) are small (few km) optical structures which have been observed close to the poleward boundary of the aurora from the high-latitude location of Svalbard (magnetic latitude 75.3 ° N). The FAEs are only visible in certain emissions and their shape has no magnetic-field aligned component, suggesting that they are not caused by energetic particle precipitation

Abstract. We propose that ionospheric plasma injections to the magnetosphere (ionospheric injection) represent a new plasma process in the polar ionosphere. The ionospheric injection is first triggered by westward electric fields transmitted from the convection surge in the magnetosphere in association with dipolarization onset. Localized westward electric fields result in local accumulation of ionospheric

Abstract. Over the hours of 5–9 UT on June 8 2001, the extreme ultraviolet (EUV) instrument onboard IMAGE satellite observed a Shoulder-like formation in the morning sector and a Plume-like structure straddling in the between noon and dusk region. Simulation results of the plasmapause formation based on mechanism of drift motion called Test Particle Model (TPM) and have reproduced various plasmapause

Understanding the atmospheric forcing from energetic particle precipitation (EPP) is important for climate simulations on decadal time scales. However, presently there are large uncertainties in energy flux measurements of electron precipitation. One approach to narrowing these uncertainties is by analyses of EPP direct atmospheric impacts and their relation to measured EPP fluxes. Here we use observations

Kinetically driven plasma waves are fundamental for a description of the thermodynamical properties of the Earth's magnetosheath. The most commonly observed ion-scale instabilities are generated by temperature anisotropy of the ions, such as the mirror and proton cyclotron instabilities. We investigate here the spatial resolution dependence of the mirror and proton cyclotron instabilities in a global

We use Van Allen Probes (Radiation Belt Storm Probes A and B, henceforth RBSP-A and RBSP-B) and GOES-13 and GOES-15 (henceforth G-13 and G-15) multipoint magnetic field, electric field, plasma, and energetic particle observations to study the spatial, temporal, and spectral characteristics of compressional Pc5 pulsations observed during the recovery phase of a strong geomagnetic storm on 1 January 2016

This study uses hourly meteor wind measurements from a longitudinal array of 10 high-latitude SuperDARN high-frequency (HF) radars to isolate the migrating diurnal, semidiurnal, and terdiurnal tides at mesosphere–lower-thermosphere (MLT) altitudes. The planetary-scale array of radars covers 180∘ of longitude, with 8 out of 10 radars being in near-continuous operation since the year 2000. Time series

This paper presents a study of diurnal tidal winds observed simultaneously by two meteor radars located on each side of the Equator in the equatorial region. The radars were located in Santa Cruz, Costa Rica (10.3∘ N, 85.6∘ W) (hereafter CR) and São João do Cariri, Brazil (7.4∘ S, 36.5∘ W) (hereafter CA). The distance between the sites is 5800 km. Harmonic analysis has been used to obtain amplitudes

Abstract. Variations of parameters of twice-ionized helium ions – He++ ions or α-particles – in the solar wind plasma during the interplanetary shock front passage are investigated. We used the data measured by the BMSW (Bright Monitor of Solar Wind) instrument installed on the SPEKTR-R satellite, which operated since August 2011 to 2019 and registered 57 interplanetary shocks. According to received

Predicting the maximum intensity of geomagnetic activity for an upcoming solar cycle is important in space weather service and for planning future space missions. This study analyzed the highest and lowest 3-hourly aa index (aaH∕aaL) in a 3 d interval, smoothed by 363 d to analyze their variation with the 11-year solar cycle. It is found that the maximum of aaH (aaHmax) is well correlated with the

Abstract. We present a statistical survey of large amplitude, asymmetric plasma, and magnetic field enhancements at comet 67P/Churyumov-Gerasimenko from December 2014 to June 2016. The aim is to provide a general overview of these structures' properties over the mission duration. At comets, nonlinear wave evolution plays an integral part in the development of turbulence and in particular facilitates

Abstract. The ionospheric Total Electron Content (TEC) provided by the International GNSS Service (IGS), and the Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) model simulated TEC have been used to investigate the delayed ionospheric response against solar flux and its trend during the years 2011 to 2013. The analysis of the distinct low and mid-latitudes TEC response over 15° E

Abstract. In this study, we analyze the climatology of ionosphere over Nepal based on GPS derived VTEC observed from four stations: KKN4 (27.80° N, 85.27° E), GRHI (27.95° N, 82.49° E), JMSM (28.80° N, 83.74° E), DLPA (28.98° N,82.81° E) during years 2008 to 2018. The study illustrates the diurnal, monthly, annual, seasonal and solar cycle variations of VTEC during all time of solar cycle 24. The results

Abstract. This paper presents the first simultaneous four radar frequency observations of the PMSE region under varying neutral air turbulence conditions. Radar frequencies of 8, 56, 224, and 930 MHz are used in this study. Three days of experimental observations associated with EISCAT are presented. Numerical simulations of mesospheric dusty/ice plasma associated with the observed radar frequencies

Abstract. The maximum of Proton Induced X-ray Emission analytical technique on metamorphic rocks in geology has used 3 MeV range proton beams for excitation of thick targets. Protons of such energies do not accurately excite K-X–rays for high Z elements in matrix geological compositions like charnockite. In this analysis, low-energy PIXE (LE-PIXE) uses K-X-rays of Low Z elements and L-X-ray series

Abstract. This study investigates the use of a vespagram-based approach as a tool for multi-directional comparison between simulated microbarom soundscapes and infrasound data recorded at ground-based array stations. Data recorded at the IS37 station in northern Norway during 2014–2019 have been processed to generate vespagrams (velocity spectral analysis) for five frequency bands between 0.1 and 0

Abstract. Ground-based observations show a phase shift in semi-annual variation of excited hydroxyl (OH*) emissions at mid-latitudes (43° N) compared to those at low latitudes. This differs from the annual cycle at high latitudes. We examine this behaviour utilising an OH* airglow model which was incorporated into the 3D chemistry-transport model (CTM). Through this modelling, we study the morphology

Abstract. In the publication Troshichev et al. (2006) on the Polar Cap (PC) indices, PCN (North) and PCS (South), an error was made by using components of the Interplanetary Magnetic Field (IMF) in their Geocentric Solar Ecliptic (GSE) representation instead of the prescribed Geocentric Solar Magnetosphere (GSM) representation for calculations of index scaling parameters in the version AARI_1998-2001

Abstract. The only published description of the solar wind sector (SS) term used for the reference level in the post-event and real-time derivation of the Polar Cap (PC) indices, PCN (North) and PCS (South), in the version endorsed by the International Association for Geomagnetism and Aeronomy (IAGA) is found in the commented publication, Janzhura and Troshichev (2011): Identification of the IMF sector

Abstract. Thermal and subthermal electron populations in the Earth's magnetotail are usually characterized by pronounced field-aligned anisotropy that contributes to generation of strong electric currents within the magnetotail current sheet. Formation of this anisotropy requires electron field-aligned acceleration, and thus likely involves field-aligned electric fields. Such fields can be carried

This study developed a model of total electron content (TEC) over the African region. The TEC data were obtained from radio occultation measurements done by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites. Data during geomagnetically quiet time (Kp < 3 and Dst > −20 nT) for the years 2008–2011 and 2013–2017 were binned according to local time, seasons

Two-dimensional (2D) test particle simulations based on shock profiles issued from 2D full particle-in-cell (PIC) simulations are used in order to analyze the formation processes of ions back streaming within the upstream region after interacting with a quasi-perpendicular curved shock front. Two different types of simulations have been performed based on (i) a fully consistent expansion (FCE) model

Abstract. Sporadic-E (Es) is generally associated with a thin-layered structure present in the lower ionosphere mostly consisted of metallic ions. This metallic ion layer is formed when meteors burn in the upper atmosphere resulting in the deposition of free metal atoms and ions. Many studies have attributed to the presence of Es due to metallic ion layer, specifically during the nighttime. Using data

Abstract. Mesoscale Convective Systems (MCS) are especially visible in the summertime, when there is an advection of warm maritime air from the West. Advection of air masses is enriched by water vapour, which source can be found over the Mediterranean Sea. In propitious atmospheric conditions, thus significant convection, atmospheric instability or strong vertical thermal gradient, lead to the development

Pulsating aurora (PsA) is a diffuse type of aurora with different structures switching on and off with a period of a few seconds. It is often associated with energetic electron precipitation (>10 keV) resulting in the interaction between magnetospheric electrons and electromagnetic waves in the magnetosphere. Recent studies categorize pulsating aurora into three different types – amorphous pulsating

The accuracy and availability of satellite-based applications, like Global Navigation Satellite System (GNSS) positioning and remote sensing, crucially depend on the knowledge of the ionospheric electron density distribution. The tomography of the ionosphere is one of the major tools for providing links to specific ionospheric corrections and studying and monitoring physical processes in the ionosphere

Abstract. In this paper, we study the response of the mesosphere and lower thermosphere (MLT) to sudden stratospheric warmings (SSWs) and the activity of stationary planetary waves (SPWs). We observe the 557.7-nm optical emission for retrieve the MLT wind, temperature with the Fabry-Perot interferometer (FPI) that has no analogues in Russia. The FPI is located at the mid-latitudes of Eastern Siberia

The most intense ionospheric storm observed in recent times occurred between 29 and 31 October 2003. The disturbances to the high-latitude regions set off several large-scale travelling ionospheric disturbances (LSTIDs), wave-like perturbations in the ionospheric electron density. This paper investigates one particular TID on 31 October 2003 using North American Global Positioning System (GPS) receiver

A solar-flare-induced, high-latitude (peak at 70–75∘ geographic latitude – GGlat) ionospheric current system was studied. Right after the X9.3 flare on 6 September 2017, magnetic stations at 68–77∘ GGlat near local noon detected northward geomagnetic deviations (ΔB) for more than 3 h, with peak amplitudes of >200 nT without any accompanying substorm activities. From its location, this solar flare effect

Aurora observations are an uncommon phenomenon at low and mid latitudes that, at the end of the 18th century, were not well known and understood. Low and mid geomagnetic latitude aurora observations provide information about episodes of intense solar storms associated with flares and outstanding coronal mass ejection (CME) and about the variation of the geomagnetic field. However, for many observers

The numerical climate simulations from the Brazilian Earth System Model (BESM) are used here to investigate the response of the polar regions to a forced increase in CO2 (Abrupt-4×CO2) and compared with Coupled Model Intercomparison Project phase 5 (CMIP5) and 6 (CMIP6) simulations. The main objective here is to investigate the seasonality of the surface and vertical warming as well as the coupled