Структура и динамика полярных токовых систем : материалы международного симпозиума «Полярные геомагнитные явления», 25-31 мая, Суздаль, СССР / Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т. – Апатиты : [б. и.], 1988.

model. Pig. 2. Tearing mode instability in 2-dimeneional model with non-zero perpendicular component of the magnetic field. even strengthened by Coroniti /8/ and Lembege and Pellet /9/. The reason why the two-dimensional case is rather stable, is the adiabatic response of the thermal electrons, magnetized everywhere inside the field reversal, to any perturbation. Hence, no effective energy exchange between the growing negative energy wave and plasma particle may take place. Recently we have analized the charged particle motion in a magnetic field reversal structure /10, 11/. We have found that the bulk of thermal electrons hardly behave adiabatically in the plasmasheet: a transition from regular to a weakly chaotic behaviour is typical for these electrons. Weakly chaotic means that large fractions of the particle motion follows rather regular adiabatic trajectories, but during some part of their motion the adiabacity condition breaks down. If these nonadiabatio fractions are small enough, the whole trajectory may be considered as almost regular, with small but practically uncorrelated jumps of the first adiabatic invariant - the magnetic moment - during any cicle of the slower motion. We have found that the dynamical properties of the particle motion in a magnetotail-like field reversal are mainly controlled by the parameter эе= Вп/в0 -(Ь/р0 )У2 where B Q and Bn are the characteristic tangential and normal to the reversal region field components and L denotes its characteristic width, ‘ j vQ is the particle's total velocity and SI 0 is the Larmor-frequency in a field B Q . If Эе» < the motion is regular; the equations of motion are inte- grable. Due to the large difference between the two main frequencies - the Larmor and the bounce frequency - an adiabatic expansion is possible and the 71