In this paper we report plasma blob events (plasma density enhancements) that were observed from KOMPSAT‐1 (685‐km altitude, 2250 LT) and DMSP F15 (840‐km 2130 in the low‐latitude F region. The blobs mostly along ±15° magnetic latitudes. Their global distribution showed a seasonal‐longitudinal dependence similar to of equatorial bubbles. drifted upward relative ambient plasma, electron temperatures H + proportions lower within compared those background. characteristics Therefore, it is...

Abstract The recent Parker Solar Probe observations of type III radio bursts show that the effects finite background magnetic field can be an important factor in interpretation data. In present paper, on plasma-emission process, which is believed to main emission mechanism for solar coronal and interplanetary bursts, are investigated by means particle-in-cell simulation method. ambient systematically surveyed varying ratio plasma frequency electron gyrofrequency. study shows a sufficiently...

[1] The radial diffusion process can play an important role in redistributing the radiation belt electron fluxes. In this work, we have performed 1-D simulations to examine evolution of phase space density (PSD) outer electrons and estimate corresponding fluxes during storm recovery phase. key element that distinguishes our from previous works is initial condition for PSD, which characterized by a steep gradient across trapping boundary. simulations, formed as result drift loss effect...

Abstract We have studied the spectral properties of quiet‐time electromagnetic ion cyclotron (EMIC) waves following a steady quiet condition, which is defined with K p values ≤1 during 12 h, using GOES 10, 11, and magnetometer data for solar minimum years 2007–2008. identified 6584 EMIC wave samples semiautomated procedure. Approximately 82% were observed in morning‐to‐early afternoon sector (0700–1500 magnetic local time) maximum occurrence near noon, their peak frequencies mostly He band....

We investigated the global distribution of equatorial plasma bubbles (EPBs) using in situ density measurements from Korea Multipurpose Satellite‐1 (KOMPSAT‐1) and Defense Meteorological Satellite Program (DMSP) F15 during solar maximum period June 2000 to August 2001. The results were generally consistent with those previous studies. EPBs observed at all longitudes around magnetic dip equator equinoctial seasons peak occurrence American‐Atlantic‐African regions. During solstice, occurred...

We investigated the properties of physical parameters during earthward flow burst (FB) events in near‐Earth magnetic tail. For investigation, we used measurements made by two Cluster satellites, C1 and C4, from 2001 to 2003 selected FB based on a set strict criteria. First, while confirmed well‐known fact that FBs are characterized generally having lower density than their surrounding medium, newly found maximum speed is statistically proportional depletion amount relative medium . Namely,...

Abstract Finite heat flux often exists in space and astrophysical plasmas, which can be a free energy source for instability. The solar wind is well-known example of such plasmas number previous studies have investigated the characteristics instability context wind. In literature there some uncertainties regarding properties While linear theories predict association with right-hand polarized whistler waves, other argue left-hand unstable modes. present study investigates nonlinear...

We study the two storm events of 1997: one in May that was accompanied by a relativistic electron event (REE) and other September, with more profound Dst decrease, but no significant flux increase electrons. find larger amount seed electrons present compared to September storm, whereas ULF (ultra low frequency) power enhanced particle spectrum harder event. Hence, we demonstrate does not necessarily produce is an important factor actual REE levels. note whistler mode chorus could also...

Abstract The whistler anisotropy (or electromagnetic electron cyclotron) instability may be operative in many geomagnetic and heliospherical environments, including the radiation belt, solar wind, corona. present investigation carries out a comparative analysis between two‐dimensional particle‐in‐cell simulation of weakly growing velocity moment‐based quasi‐linear theory under assumption bi‐Maxwellian distribution function. It is shown that simplified provides qualitative agreement with more...

Abstract We have studied the statistical properties of low‐energy proton (H + ) and helium (He ion flux enhancements associated with electromagnetic cyclotron (EMIC) waves in inner magnetosphere using Van Allen Probes data for 2013–2017. identified 167 when EMIC occurred a He‐band or multiple band (H‐band He‐band) strong weak H‐band wave activity found that most them from noon to premidnight sector near magnetic equator just inside plasmapause. Of enhancement events, 68 exhibited only He...

In particle-in-cell (PIC) simulation studies of ion-ion two-stream instability, a reduced ion-to-electron mass ratio is often employed to save computation time. It tacitly assumed that electrons do not play significant role in the evolution instability as interactions are regarded occur on time scales much slower than response electrons. However, effect such has never been closely examined, we have studied ion beam driven using one-dimensional electrostatic PIC code by rescaling parameters...

We have developed a 2.5-dimensional electromagnetic particle simulation code using the particle-in-cell (PIC) method to investigate phenomena that occur in space plasmas. Our is based on leap-frog and centered difference for integration differentiation of governing equations. adopted relativistic Buneman-Boris solve Lorentz force equation Esirkepov calculate current density while maintaining charge conservation. Using code, we performed test simulations electron two-stream instability...

Abstract Electromagnetic ion cyclotron (EMIC) waves generated by hot anisotropic (T ⊥ > T ∥ ) protons (∼10–100 keV), play an important role in accelerating cold (<1 eV) (H + and helium (He ions the magnetosphere. Using a hybrid code with parameters found inner magnetosphere, we examine when how H He are energized EMIC waves. Hybrid simulations show that energization of particles occurs two steps. In first step, waves, which linearly excited early stage simulation, interact ions,...

In this paper, we investigated the electron Debye scale Kelvin-Helmholtz (KH) instability using two-dimensional electrostatic particle-in-cell simulations. We introduced a velocity shear layer with thickness comparable to length and examined generation of KH instability. The occurs in similar manner as observed instabilities fluid or ion scales producing surface waves rolled-up vortices. strength growth rate is affected by structure layer. depends on magnitude gradient However, development...

In this study, we investigated the effect of space plasmas on floating potential variation a low-altitude, polar-orbiting satellite using Langmuir Probe (LP) measurement onboard STSAT-1 spacecraft. We focused small drops, for which estimation plasma density and temperature from LP is available. The varied according to variations temperature, similar previously reported observations. Most drops occurred around nightside auroral region. However, unlike previous studies where large were...

We statistically investigated the properties of low-latitude Pi2 pulsations using Bohyun (BOH, Mlat = <TEX>$29.8^{\circ}$</TEX>, L 1.35) ground magnetometer data in 2008. For this 1-year interval, 582 events were identified when BOH was nightside from 1800 to 0600 local times. found following characteristics. (1) The occurrence distribution Pi2s is relatively constant (2) frequency varies That is, postmidnight sector had higher than premidnight sector. (3) power stronger (4) has positive...

Numerical solutions to floating plasma potentials for walls emitting secondary electrons are obtained various surface materials. The calculations made with moment equations and the electron emission coefficients, which were determined from recent laboratory experiments. results estimate wall up physical conditions that allow stable sheaths under space-charge-limited condition. materials often used in laboratory, such as aluminum, silicon, boron, molybdenum, silicon dioxide, alumina,...

In this paper we present analysis of current density when the Cluster spacecraft pass nightside auroral region at about 4-5 RE from center Earth. The is made inter-spacecraft separation within 200 km, which allows all four to be situated inside same sheet. On 22 February 2002, two field-aligned (FAC) events were observed in both southern and northern hemispheres. FACs calculated with magnetic field data obtained by using Curlometer method. scales along trajectory magnitudes hundreds...

Three‐dimensional magnetic reconnection is studied using magnetohydrodynamic simulations. The initial configuration based on the two‐dimensional Harris neutral sheet model that lies in xz plane and extended y direction. Localized anomalous resistivity applied to central region, subsequent evolution of spontaneous observed. Special attention given results with a finite B superimposed model. Significant changes are seen morphology, as component causes asymmetries. reconnected field lines...

This paper describes the initial operations and preliminary results of Instrument for study Stable/Storm-time Space (ISSS) onboard microsatellite Next Generation Small Satellite-1 (NEXTSat-1), which was launched on December 4, 2018 into a sun-synchronous orbit at an altitude 575 km with orbital inclination angle 97.7°. The spacecraft instruments have been working normally, from observations are in agreement those other satellites. Nevertheless, improvement both spacecraft/instrument...

Abstract Studies of shocks have long suggested that a shock can undergo cyclical self-reformation on timescale ion cyclotron period. This process has been proposed as primary mechanism for energy dissipation and energetic particle acceleration at shocks. Unambiguous observational evidence, however, remained elusive. Here, we report direct observations the collisionless, high Mach number, quasi-perpendicular using Magnetospheric Multiscale (MMS) measurements. We find reflected ions by old...