ON SPONTANEOUS RECONNECTION IN THE EARTHS MAGNETOTAIL

The release of energy stored in the Earth's magnetotail is a major feature of the coupling between solar wind and magnetosphere. Spontaneous reconnection due to tearing mode instability in the magnetotail provides an appropriate mechanism, explaining energy release, delays the response to changes in the interplanetary medium, non stationary features of the magnetospheric behaviour. Problems, however, exist in the theory of spontaneous reconnection. Here in this paper new theoretical results are discussed, which help to advance the understanding of collisionless nonstationary reconnection processes in the tail. It is discussed, how the stabilizing influence of adiabatic electrons can be canceled. Further it is shown that in addition to the instability of a shearless tail, usually discussed, another route to instability appears in the presence of a finite magnetic shear. Finally the transition to a nonlinear, explosive mode of instability is examined.