Three-dimensional computer modeling of dynamic reconnection in the magnetotail

Two- and three-dimensional computer models of the dynamics of the magnetosphere and in particular the magnetotail have shown, that the basic features of the idealized linear or steady state reconnection theory are still found in time dependent and spatially more complicated configurations such as the magnetotail, which basically resembles a plane sheet pinch but in addition has small magnetic field components perpendicular to the sheet, field line flaring and variations along both directions parallel to the current sheet. These basic features are the formation of a magnetic neutral x-line or separator, where two surfaces separating magnetic fluxes of different topology intersect, with the generation of an electric field along the separator and the production of strong plasma flows parallel to the current sheet away from the separator in opposite directions. In addition, the computer models of magnetotail dynamics have produced many large scale features that are directly observed or deduced from observation in relation with magnetospheric substorms. Among those features are: the thinning of the plasma sheet, the formation of a plasmoid, a region of closed magnetic loops detached from Earth, which moves tailward at a speed of several hundreds of km/sec, and the generation of field-aligned currents. In view of the recent discovery of plasmoid signatures in the distant magnetotail at about 200 R/sub E/ from ISEE-3 satellite measurements, we discuss the properties of the plasmoid in the computer simulations, in particular its topology, spatial extent and speed, the current system associated with it and its local appearance at a fixed location in space. Furthermore, we discuss the conversion of the energy flux around the separator, current deviations and the occurrence of field-aligned currents and their generation by shear flows. 10 references, 21 figures, 2 tables