I.P. Kirpichev

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.

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.

Cusp energetic particles observed by INTERBALL-tail probe in 1996

Abstract The protons with energies of 1 – 3 MeV were observed in the dayside cusp by INTERBALL-Tail Probe. The flux increases lasting for several tens of minuttes were recorded up to the magnetopause. These energetic particle enhancements were accompanied by low-frequency wave turbulence.

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.

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.

Estimation of the current density and analysis of the geometry of the current system surrounding the Earth

The results of an investigation of the distribution of plasma pressure, pressure gradients, and magnetic field near the equatorial plane in the plasma ring surrounding the Earth under magneto-quiet conditions are presented. Observational data obtained during the international THEMIS mission are used. The picture of the distribution of transverse-current density near the equatorial plane was obtained under assumption of observing the magnetostatic balance condition at geocentric distances from 6 to 12RE. In estimating the integral transverse current it was accepted that in daytime sector the magnetic-field minima on magnetic field lines are not localized in the equatorial plane. Estimates of the integral transverse current were obtained, which demonstrate the possibility of closing nighttime transverse currents at geocentric distances of up to ∼12RE inside the magnetosphere, which form a high-latitudinal continuation of the ring current.

Magnetospheric substorms and discrete arcs of the polar aurora

A brief review of the results of the research in physics of the Earth’s magnetosphere leading to a substantial modification of the previously developed approaches is presented. The main emphasis is placed on physics of magnetospheric substorms and the nature of auroral arcs. It is shown that the formation of powerful electron beams that produce multiple arcs can be associated with the penetration of cold electrons of an ionospheric origin into the region of field-aligned acceleration of hot magnetospheric electrons.