Particle dynamics and currents in the magnetotail

This paper is a brief summary of our studies of magnetotail phenomena, based on the motion of charged particles and on electric currents. Theory and satellite data have been used together to obtain quantitative understanding. A guiding center theory similar to that of the usual Alfven's guiding center theory has been developed. In the region where the magnetic field is small or equal to zero, the circular motion becomes an 8-shaped motion, and the magnetic moment is equivalent to two opposite magnetic moments. An analytical trajectory of the particle motion has been found in the neutral sheet magnetic field. In the more general case, in the neutral line magnetic field, a particle computer simulation has been used, studying the accelerations, the pitch angular scattering and the propagation of a point source plasma in the magnetotail. Some current descriptions in the magnetotail are discussed. The plasma current sheet was found from the solution of a time-independent Vlasov equation, and the relation between the particle motion and the magnetic field is a selfconsistent system. The authors derive an expression for a 3-dimensional function of a field-aligned current. Moreover, some simple model of the filamentary current found by the satellite data in the magnetotail lobe is discussed. Finally, the authors analyze the particle and magnetic field data observed by IMP-7, IMP-8, and ISEE-1, and found the drawn-dusk asymmetry of the particles in the neutral sheet, the magnetic current sheet, and the filamentary current in the magnetotail lobe, which are comparable to the theoretical results