HYBRID SIMULATIONS OF WHISTLER WAVES GENERATION AND CURRENT CLOSURE BY A PULSED TETHER IN THE IONOSPHERE

The dynamic response of a magnetized collisionless plasma to an extern ally driven, finite size, sudden switch-on current source across the m agnetic field has been studied using a two dimensional hybrid code. It was found that the predominant plasma response was the excitation of whistler waves and the formation of current closure by induced current s in the plasma. The results show that the current closure path consis ts of: a) two antiparallel field-aligned current channels at the end o f the imposed current sheet; and b) a cross-field current region conne cting these channels. The formation of the current closure path occure d in the whistler timescale much shorter than that of MHD and the clos ure region expanded continuously in time. The current closure process was accompanied by significant energy loss due to whistler radiation.