E. E. Antonova

Magnetostatic equilibrium and current systems in the Earth’s magnetosphere

Abstract Experimental observations of the plasma pressure distribution in the magnetosphere including the latest data from INTERBALL/Tail probe are summarized. Generation of transverse and field-aligned currents due to the magnetospheric plasma pressure gradients is analyzed. Formation of the inner magnetospheric current systems and their configuration are discussed. Arrangement of the observed plasma pressure profile is analyzed with allowance for the turbulent plasma transport and self-organized criticaliry in the magnetosphere.

THE INFLUENCE OF THE ENERGETIC TAILS OF ION DISTRIBUTION FUNCTION ON THE MAIN PARAMETER OF THE THEORY OF FIELD-ALIGNED CURRENT SPLITTING AND INTERCOSMOS-BULGARIA-1300 OBSERVATIONS

Abstract The theory of hot plasma stratification in the region of upward field-aligned current suggests the condition of the magnetostatic equilibrium and plasma pressure variation directly related to magnetospheric potential variation. This theory was developed using a Maxwellian shape for the plasma distribution function and the assumption of a definite temperature. Such an approximation underestimate the contribution of energetic particles to the plasma pressure. The use of kappa distributions, alternatively, results in a more correct value of the main parameter of the theory of hot plasma splitting. The theoretical analysis is compared with the results of experimental observations published by Antonova et al., 1998.

Large scale magnetospheric turbulence and the topology of magnetospheric currents

Abstract Interball project includes comparison of experimental observations with existing magnetospheric theory predictions and the development of new approaches to the description of magnetospheric processes. As a result of such an investigation a self-consistent theory of large- and medium-scale magnetospheric convection was suggested. The main source of large-scale magnetospheric convection in this theory is the topology of magnetospheric currents. The observed reconnection processes on the magnetopause and in the tail are treated as the result of the modulation of inner magnetospheric currents by the interplanetary magnetic field (IMF). The dawn-dusk electric field and smaller scale electric fields arise as the harmonics of the unstable plasma distribution. The observed quasi-stationary plasma distribution and the existence of the periods of stable convection in the magnetosphere are explained due to the development of medium- and small-scale electric fields and intense plasma sheet plasma mixing. The theory naturally explains dawn-dusk electric field dependence on IMF orientation, maximum dawn-dusk potential drop mapping on the inner magnetosphere regions, daytime magnetopause erosion and tail current growth when IMF has a southward orientation and many other effects.

Investigations of the hot plasma pressure gradients and the configuration of magnetospheric currents from interball

Abstract One of the main aspects of the multi satellite INTERBALL program is connected with the experimental determination of the hot plasma pressure distribution inside the magnetosphere and the solution of the well known problem of the inner magnetosphere substorm onset. The main results of the experimental observations, the structure of high latitude currents and the modeling of the magnetospheric processes are discussed. Observations of particles in a wide energy range from tens of eV to Mev energies give the possibility to construct the full distribution function and to calculate plasma pressure. Quiet time plasma pressure profiles show the regularity and the increase of the pressure with the decrease of the geocentric distance. The observed region of plasma pressure plateau means the existence of nearly zero transverse and field-aligned current regions. The existence of such a region gives the possibility to explain the observed gap between Region 1 and Region 2 currents. Investigations of the fluctuations of the plasma bulk velocity inside the plasma sheet support the existence of plasma sheet turbulence. The existence of plasma sheet turbulence explains the inner magnetosphere substorm onset as only stable before substorm plasma region can become unstable. The introduction of the turbulent transport in the model of the plasma sheet and the theory of the plasma sheet with medium-scale turbulence are discussed

Plasma pressure distribution in the equatorial plane of the Earth’s magnetosphere at geocentric distances of 6–10RE according to the international THEMIS mission data

The structure of the averaged plasma pressure distribution in the plasma ring around the Earth at geocentric distances of ∼6–10RE has been determined. The distribution function moments measured on the international THEMIS mission satellites have been used. The plasma pressure distribution in the equatorial plane at 15RE > XSM > −15RE and 15RE > YSM > −15RE has been statistically studied. The radial dependence of the plasma pressure at the day-night and morning-evening meridians has been analyzed. It has been indicated that the plasma ring around the Earth has a structure, which is close to being azimuthally symmetric. The achieved results have been compared with the pressure distributions obtained previously. It has been indicated that in the overlapping regions, the achieved results agree with the previously obtained data within the pressure determination errors.

Pressure balance on the magnetopause near the subsolar point according to observational data of the THEMIS project satellites

An analysis of the pressure balance on the magnetopause near the subsolar point has been made for 18 crossings of the magnetopause by the THEMIS project satellites under magneto-quiet conditions. Dynamic and static pressures of plasma are determined, as well as magnetic pressure in the magnetosheath, and magnetic and plasma static pressure inside the magnetosphere. Variations of the total pressure have been studied in the case when one satellite is located inside the magnetosphere and another one stays in the magnetosheath near the magnetopause. It is demonstrated that for 18 investigated events the condition of pressure balance at the subsolar point is valid on average with an accuracy of 7%, within measurement errors and under applicability of the approximation of anisotropic magnetic hydrodynamics to collisionless plasma of the magnetosheath and magnetosphere.

Turbulent fluctuations of plasma and magnetic field parameters in the magnetosheath and the low-latitude boundary layer formation: Multisatellite observations on March 2, 1996

The results of simultaneous analysis of plasma and magnetic field characteristics measured on the INTERBALL/Tail Probe, WIND and Geotail satellites on March 2, 1996, are presented. During these observations the INTERBALL/Tail Probe crossed the low-latitude boundary layer, and the WIND and Geotail satellites measured the solar wind’s and magnetosheath’s parameters, respectively. The plasma and magnetic field characteristics in these regions have been compared. The data of the Corall, Electron, and MIF instruments on the INTERBALL/Tail Probe satellite are analyzed. Fluctuations of the magnetic field components and plasma velocity in the solar wind and magnetosheath, measured onboard the WIND and Geotail satellites, are compared. The causes resulting in appearance of plasma jet flows in the low-latitude boundary layer are analyzed. The amplitude of magnetic field fluctuations in the magnetosheath for a studied magnetosphere boundary crossing is shown to exceed the magnetic field value below the magnetopause near the cusp. The possibility of local violation of pressure balance on the magnetopause is discussed, as well as penetration of magnetosheath plasma into the magnetosphere, as a result of magnetic field and plasma flux fluctuations in the magnetosheath.

Azimuthal plasma pressure reconstructed by using the Aureol-3 satellite data during quiet geomagnetic conditions

Abstract The azimuthal distribution of magnetospheric plasma pressure was studied using the precipitating particle fluxes observed by the low-altitude polar-orbiting Aureol-3 satellite. The data from the 18 March 1982 event was used to calculate the pressure along the satellite trajectory during quiet geomagnetic conditions. The magnetic flux tube volumes for the field-lines, corresponding to the points of measurement at the satellite trajectory, were calculated by using Tsyganenko 96 magnetic-field model. The gradients of the plasma pressure along the isosurfaces of the volume of the magnetic flux tube per unit flux were estimated, and the field-aligned currents were calculated assuming that the condition of the magnetostatic equilibrium is valid. The results obtained were compared with the [J. Geophys. Res. 81 (13) (1976) 2165] field-aligned current distribution.

Fine structure of auroras during auroral breakup according to the ground-based and satellite observations

The dynamics and fine structure of auroras before and during 60 auroral breakups, including pseudobreakups and breakups at moderate and high auroral activity, have been studied using the developed method for processing television images. The IMAGE and POLAR satellite and simultaneous ground images of auroras, ground magnetic data, and measurements of IMF and solar wind plasma parameters have been analyzed. The signatures that can be precursors of breakup have been found out in the auroral dynamics and morphology in the spatial—temporal vicinity of breakup. The morphological characteristics of auroral structures have been analyzed statistically. The directions of motion of weak subvisual structures have been determined. The velocities of motion of such structures are presented. The relation of the initial auroral arc bright-ening during breakups and pseudobreakups to the beginning of magnetic activation and formation of rayed structures has been analyzed.

Comparison of the plasma pressure distributions over the equatorial plane and at low altitudes under magnetically quiet conditions

The distribution of plasma pressure over the equatorial plane is compared with the plasma pressure and the position of the electron precipitation boundaries at low altitudes under the conditions of low geomagnetic activity. The pressure at the equatorial plane is determined using data of the THEMIS international five-satellite mission; the pressure at low altitudes, using data of the DMSP satellites. Plasma pressure isotropy and the validity of the condition of the magnetostatic equilibrium at a low level of geomagnetic activity are taken into account. Plasma pressure in such a case is constant along the magnetic field line and can be considered a “natural tracer” of the field line. It is shown that the plasma ring surrounding the Earth at geocentric distances of ∼6 to ∼10–12RE is the main source of the precipitations in the auroral oval.