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.

Earthward electricfield in the geomagnetic current sheet Apparently, these electrons appear due to scatterings with ionospheric plasma. The direction of the electric field between the upward and downward current layers shows that field-aligned currents are generating in CS of the geomagnetic tail. Such generation demands the earthward electric field appearance in the tail CS. The potential drop ~10 kV is projected in the tail along the field line up to the distance order of 20 R e The Ohm law j = ct[E + VxB/c - jxB/nec + Vp^ne] shows that the earthward electric field can be only the Hall electric field jxB/nec. The term Vpe can be neglect in a long CS. For the tail length L-20RE and the temperature drop ~1 kV, the electric field does not exceed ~ 10'6 V/cm. It is important to emphasize that normal magnetic field component is always appeared in all CSs in the laboratory simulated magnetosphere and in space. The electron gas is accelerated by the jxB/c force. The tail current density increases during a substorm due to the decreasing of CS thickness up to ~ O.IRg. As a result the jxB/c force increases and produces accelerated plasma injection into the Earth’s magnetosphere. The Hall electric field jxB/nec also increases. For tail magnetic field Bt =20 nT, the normal magnetic field component Bn ~ 2 nT in the tail CS, the plasma density n ~ 0.2 cm'3, and the CS thickness at a substorm 5 = 0.1 Rg the potential drop at distance L = 10REcan be estimated as BtBnL/(2n8ne) ~50 kV. The independent proof of the Hall effect existence in CS manifestation is made in the laboratory experiment (Minami et al., 1993). The magnetosphere with a magnetic tail has been created at supersonic and superalfvenic plasma flow interaction with the dipole magnetic field. It has been shown that the Hall electric field generation occurs in a tail CS. The electric field is directed to the Earth’s dipole. The stream of the ions which have been accelerated by the Hall field enters the strong dipole magnetic field creating of positive space charge accumulation. In this place the opposite directed electric field is registered. Another independent evidence of the Hall effect in the geomagnetic tail has been shown by Israelevich et al., [2001], which is indicated existence in the geomagnetic CS the antiearthward current order of 1 MA. Electron or ion current in CS? For Hall effect appearance, it is necessary that the jxB/c force has to be applied to the electron gas, i.e. the considerable part of the current should be transferred by electrons. The principal role of electrons in the tail current is seen in valuable measurements of ion fluxes in the tail CS of the Earth magnetosphere ([Baumjohann at al., 1990]). The data are acquired from the AMTE/IRM satellite. It has been shown that the ion velocity component Viy directed along current in CS is always is very weak, and the earthward ion flux has been detected. These data contradict with the conclusions made by Zelenyi at al. (2002), and Sitnov at al. (2000) about current production in CS by ions. The conclusions about the current transferring by ions have been made from consideration of ion trajectories in the CS magnetic field. The magnetic tension force in the current layer is completely ignored. The conclusion is declared: “The current in CS mainly supported by the ion currents”. Such self-contained ideal CS is constructed without the force applied to magnetosphere from the solar wind. The mistake of such conclusion has been established at the analysis of direct measurements of electron fluxes in geomagnetic CS and comparison these measurements with curl measurements. In works of Runov at al. (2006) and Izrailevich at al., (2008) it has been shown that the basic contribution of the current of CS is due to electrons. Westward electrojet The electric field between layers of opposite directed FAC is perpendicular to the magnetic field. Besides the Pedersen current, it must induce Westward Hall current in the ionosphere along the polar oval. The strong FAC appears when the IKB-1300 space craft has been flown above the chain of IZMIRAN magnetic stations. The westward electrojet is revealed itself with the current ~2 104 A (Dubinin at al., 1987). The jet is located above the measured AB maximum, e. g. between upward and downward FAC layer (Fig. 3b). Here the Hall current JH =( c / 4 ti ) (EH/Sp) AB has to be exists, where E is the height integrated conductivity. Apparently the ratio 2H/£p is increased due to the fast electron precipitation. According to Reiff at al. ([1984]) the ratio is AZH/A£p ~ W5/8, where W is the electron energy in keV. The most probable scheme of the auroral electrojet short circuit has been offered by McPherron et al. (1983) (Figure. 3c). During a substorm, the part of the current of CS is connected with the electrojet via FAC, and dipolization of the Earth magnetic field occurs. On the possibility of the earthward electric field estimated by the drift approximation Recently L. M. Zelenyi et al. (2010) are offered the other mechanism of the earthward electric field generation in the geomagnetic tail The two-dimensional stationary existing configuration of the magnetic field with antiparallel lines 53