Physics of auroral phenomena : proceedings of the 34th Annual seminar, Apatity, 01 - 04 March, 2011 / [ed.: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 231 с. : ил.

I.M. Podgomy, and A.I. Podgomy compensated by the pressure gradient along the sheet and mainly by inertia of ions. As electrons in CS are magnetized, the force of a magnetic tension accelerates electronic gas. The electric charge separation takes place. Ion acceleration to the Earth occurs in the electric field of a formed space charge. In quasi stationary state plasma is flowing in CS. In the vicinity of the X-type singular line magnetic field lines are reconnected. Magnetic energy released at magnetic reconnection is used for plasma heating in CS, and the plasma is accelerated toward the Earth. Compensation of the reconnected magnetic flux occurs, apparently, with southward magnetic field component in the solar wind. The balance of magnetic energy is sharply broken during a substorm because of reconnection rate increasing. The Earthward electric field in the geomagnetic tail The Soviet-Bulgarian spacecraft IKB-1300 was launched in 1981, August 7 on a polar circular orbit with the altitude of 900 km (Podgomy at al., 1988, Dubinin at al., 1987). Three-axis stabilization supplied unique possibility of comfortable measurements of three components of the electric and magnetic fields, and the plasma velocity. The tip - tip distance of the electric field sensors was 7.5 m. X - axis is directed along the spacecraft velocity; Z - axis is directed upward normal to the Earth surface. In the auroral regions the Z- axis almost coincides with a magnetic field line. The fluxes of fast electrons, the electron spectrum, and atmosphere luminosity in several spectral lines are also measured. The measured value of the electric field component perpendicular to the Earth magnetic field is controlled by plasma drift velocity measurements in XY-plane. Ex mV/m i i i i i i i i i i i i i Ы 0 -80 0 -80 -160 2 0 -2 MLT 23.7 0.1 ILAT 63.2° 66.7° I I I I I i i i i r i I I I I I Fig. 2. Measured electric and magnetic fields, current density, and electron flux at crossing field-aligned currents by the spacecraft. Electric and magnetic fields measurements at crossing the pair of field-aligned currents at night side as shown in Fgure 2 , when the chain of IZMIRAN magnetic stations demonstrates an enhancement of the westward jet. This successful coincidence of circumstances has occurred on December 21, 1981. The measured electric field Ez normal to the Earth has been very small, and Bz magnetic field component has not been disturbed. The main upward and downward field-aligned current (FAC) layers in the night sector are recorded. The increasing magnetic filed ДВ is situated in the plane perpendicular to the Earth magnetic field (XY plane). AB is located between upward (at lower latitude) and downward (at higher latitude) FAC layers. The angle between the normal to the FAC layer and X-axis is arctan(ABx/ABy) ~ 50°. The electric field between opposed directed FAC is revealed. This electric field is directed perpendicular to the FAC layers. The total potential drop exceeds -10 kV. But there is no symmetry in North-South electric field distribution between upward and downward FAC layers. The electric field maximum is shifted to the downward current. Such distribution is a consequence of increasing the Pedersen conductivity in the region of upward current due to electron precipitation. Electrons are accelerated in upward FAC to the Earth somewhere above the spacecraft (900 km). The electron flux produces aurora neutral particle ionization in the ionosphere. The Pedersen height integrated conductivity is increasing in the precipitation region according to Д£Р= 4.7xl012[W(erg cm'2 s'1)] cm s"1[Harel at al., 1981]. Increasing ionospheric conductivity in the region of upward FAC produces redistribution of the potential drop. So, the electric field maximum is shifted to the downward current. In the region of the upward current, the weak upward electron flux is also observed. 52