CRRES POYNTING VECTOR OBSERVATIONS OF ELECTROMAGNETIC ION-CYCLOTRON WAVES NEAR THE PLASMAPAUSE

Electromagnetic ion cyclotron waves have been observed by the Air Forc e Geophysics Laboratory triaxial fluxgate magnetometer on the CRRES sa tellite in the vicinity of the plasmapause. Specific wave events in th e 1300-0100 MLT local time sector and over L = 4.8 - 6.7 at magnetic l atitudes between +/- 20 degrees have been studied with respect to ener gy propagation. Using the wave magnetic field data and the orthogonal two-component Berkeley electric field experiment data allows the compu tation of the Poynting vector. Nine events with frequencies below 0.6 Hz have been analyzed. General wave properties showed intensities in t he range 4 - 18 mu W m(-2). In most events, energy propagation was pre dominantly away from the equator, supporting the existence of an equat orial source region. There are exceptions and one event, observed 3 de grees from the equator, also showed some propagation back to the equat or with equal energy. Four periodic wave packets were seen in another event. This event showed unidirectional propagation away from the equa tor over all packets with periodicity approximately one-half of the ca lculated time for a typical bouncing wave packet. Consequently, the pe riodicity is not the signature of a classical periodic structured Pc 1 -2 pulsation event of the type seen on the ground. Generally, the resu lts for these waves with f < f(He)+ may be interpreted by assuming an ion cyclotron instability source located near the equator and irregula rly emitting wave trains of energy into one or both hemispheres, with minimal reflection at the ionosphere.