Elizaveta Antonova

Azimuthal hot plasma pressure gradients and dawn-dusk electric field formation

Abstract The effects of hot plasma pressure gradients in the high latitude magnetosphere are analysed. It is shown that such a mechanism may in fact be responsible for Region 1 field-aligned currents and for the dawn-dusk electric field. The estimated azimuthal gradients in the plasma pressure may account for the observed field-aligned currents and also give the opportunity to determine the day-night plasma pressure changes along isosurfaces of magnetic flux tube volume. These pressure changes are then compared with experimentally measured pressure distribution and it is shown that the day-night plasma change, in the high latitude magnetosphere, may be high enough to sustain Region 1 currents. The closure of these currents in the high latitude magnetosphere may in turn be responsible for the dawn-dusk electric field and the dawn-dusk potential drop in the inner plasma sheet regions. The influence of the IMF on the magnetostatically equilibrium inner magnetospheric currents may qualitatively explain the IMF control of the dawn-dusk electric field and magnetospheric activity.

The ion differential spectra in outer boundary of the ring current: November 17, 1995 case study

Abstract The analysis of the ion spectra variations is presented for the particles in the energy range from 0.5 keV to 3 MeV during INTERBALL-Tail Probe crossing of the plasma sheet-ring current region on November 17, 1995. The CORALL, DOK-2 and SKA-2 instrument data were used for spectra restoring. It is shown ion spectra have the same smooth shape (with the averaging time ∼2 min ) by traversing the satellite from 20Re up to 6Re. In particular, the spectra shape was almost constant with decreasing of geocentric distance from Re=11 to 6. Possible reasons of spectra variations are discussed.

Multiple inverted‐V structures and hot plasma pressure gradient mechanism of plasma stratification

A mechanism of plasma stratification within the inner plasma sheet is discussed. It is suggested that plasma pressure is isoptropic and particle motion is unmagnetized for the spatial scales in which the structures are formed. The solution of the magnetosphere-ionosphere interaction problem shows that upward field-aligned current may split into separate structures. The number of structures formed is determined by a parameter which depends on upward field-aligned current density, field-aligned current band width, hot magnetospheric ion temperature, and height-integrated Pedersen ionospheric conductivity. The Intercosmos-Bulgaria-1300 satellite base data has been used to identify events of multiple inverted-V structures. It is shown that the hot stratification plasma mechanism offers a good description of the number of observed structures.

Determination of the Turbulent Diffusion Coefficient in the Plasma Sheet Using the Project INTERBALL Data

The results of an analysis of velocity fluctuations in the plasma sheet of the Earths magnetotail measured onboard INTERBALL Tail Probe satellite are presented. The hodographs of the velocity in directions (Y, Z) and correlation functions are presented for a number of passages when the satellite was in the plasma sheet for a long time. The turbulent diffusion coefficients are calculated. A comparison of the obtained diffusion coefficients with those predicted theoretically in [1] is carried out. It is shown that the results of observations confirm theoretical predictions.

Generation of unmagnetized motion of plasma sheet electrons and its possible causes

Results of experimental and theoretical studies of unmagnetized stochastic motion of the plasma sheet electrons and the mixing of plasma in the plasma sheet are presented. Analysis of the electron temperature distributions within the plasma sheet is undertaken using the data from Intercosmos-Bulgaria-1300 polar orbiting satellite. The electron temperature is obtained with consideration of acceleration of precipitating electrons by the field-aligned potential drop; this temperature is nearly constant in the meridional direction and has no longitudinal dependence during quiet geomagnetic conditions. Analysis of spacial fluctuations of precipitating electron fluxes for a fixed electron energy shows that fluctuation spectra of primary electrons have a power dependence and resemble the spectra of electric field fluctuations observed within the plasma sheet. The satellite observations are interpreted in terms of stochastic motion of the plasma sheet electrons and intensive mixing of plasma in the sheet. It is suggested that the electron motion in the electric field with a characteristic scale comparable with the electron Larmor radius is a source of stochastization; chaotization of the particle trajectories could be a part of stochastization process. The particle motion in a homogeneous magnetic field and in a regular inhomogeneous electric field with a sinusoidal distribution in one direction and a homogeneous distribution in the perpendicular direction is analyzed as an example of the chaotic motion.

Role of turbulent transport in the evolution of the κ distribution functions in the plasma sheet

We studied the evolution of ion and electron distribution functions, approximated by κ distributions, in the plasma sheet with the distance from the Earth using the data of the Time History of Events and Macroscale Interactions during Substorms spacecraft mission. Five events were used to calculate the main parameters of the κ distribution. For these events at least four spacecraft were aligned along the tail between approximately 7 and 30 RE. It was found that for the majority of events the values of κ increase tailward. The observed radial profiles could be related to the inner magnetosphere sources of particle acceleration and to the net tailward transport of particles. This net transport is the result of a balance between the average regular bulk transport toward the Earth and the turbulent transport by eddies in the tailward direction.

The development of initial substorm expansive phase disturbance due to generation of localized electric fields in the region of maximum upward field-aligned current

Abstract The analysis of the plasma sheet plasma stability for the small scale electrostatic disturbances in the simple approximation of one fluid magnetohydrodynamics show that the region of upward field-aligned current near midnight where fast radial plasma flow take place can become unstable to localized electrostatic disturbances during the growth phase of substorms. Such instability can explain the onset of substorm deep in the magnetosphere near the Earths border of the tail current sheet.

Topology of High-Latitude Magnetospheric Currents

The structure and localization of high latitude transverse and field-aligned currents are analyzed using the data from the Themis satellite mission. A number of evidences resumed in this paper, including daytime compression of magnetic field lines and the existence of magnetic field minima far from the equatorial plane make necessary to reanalyze the traditional points of view about the topology of high-latitude magnetospheric currents. Comparison between the dayside integral transverse currents at the geocentric distances 7–10R E , calculated assuming the validity of the condition of magnetostatic equilibrium and the nighttime transverse currents, showed that ordinary ring current has the high latitude continuation until geocentric distances ∼10–13R E . The problem of the location of Region 1 field-aligned current of Iijima and Potemra is discussed.

Dependence of magnetic field parameters at the subsolar point of the magnetosphere on the interplanetary magnetic field according to the data of the THEMIS experiment

We analyze the dependence of the magnitude of the magnetic field, its three components, and the clock angle in the magnetosheath just in front of the magnetopause on the same values in the solar wind before a shock wave using the data of the THEMIS experiment. We take into account the time delay of the solar wind arrival at the subsolar point of the magnetopause. We obtain dependencies of the components of the magnetic field and the clock angle at the magnetopause on the corresponding quantities in the solar wind for different averaging intervals. We point to the events for which the direction of the magnetic field at the magnetopause is highly different from the direction of the magnetic field in the solar wind up to the sign change.

The model of turbulent plasma sheet during IMF Bz > 0

Abstract Theory of the plasma sheet with medium-scale developed turbulence gives the possibility to explain the main processes of plasma sheet bifurcation and theta-aurora formation during IMF B z > 0. The model suggests that during IMF B z > 0 small bulge structure in the plasma sheet center is formed. The polarization of the bulge due to dawnward electron motion and duskward ion motion decreases the large-scale electric field in the bulge region. The decrease of the large-scale field in the conditions of constant coefficient of diffusion leads to the bulge growth. The results of plasma sheet bifurcation and theta-aurora formation modelling are presented.