Dynamics of the plasma sheet in the magnetotail: Interrelation of turbulent flows and thin current sheet structures

Abstract

Dynamics of the magnetotail involves elementary processes of magnetic field merging (reconnection layer formation) occurring on medium spatial scales. Every such process features two different stages, a fast one and a subsequent slower one. The corresponding short time scale T 1 is associated with disturbances propagating in the tail lobes. The longer time scale T 2 is associated with plasma motions in the plasma sheet. A disturbance appearing in the magnetotail on the time scale T 1 results in a loss of equilibrium in the plasma sheet. By means of theoretical argument and numerical simulation, it is shown that the relaxation process which follows on the time scale T 2 , produces extremely thin embedded current sheets, along with generation of fast plasma flows. The process provides an effective mechanism for transformation of magnetic energy accumulated in the magnetotail, into energy of plasma flows. The fast flows may drive turbulent motions on shorter spatial scales. In their turn, those motions can locally produce very thin current sheets; after that, nonlinear tearing process leads to generation of neutral lines, and reconnection. The latter produces new fast disturbances on the time scale T 1 closing the feedback loop.