Abstract
Electromagnetic ion cyclotron waves have been observed by the Air Force Geophysics Laboratory triaxial fluxgate magnetometer on the CRRES satellite in the vicinity of the plasmapause. Specific wave events in the 1300–0100 MLT local time sector and over L = 4.8 – 6.7 at magnetic latitudes between ± 20° have been studied with respect to energy propagation. Using the wave magnetic field data and the orthogonal two‐component Berkeley electric field experiment data allows the computation of the Poynting vector. Nine events with frequencies below 0.6 Hz have been analyzed. General wave properties showed intensities in the range 4–18 μW m−2. In most events, energy propagation was predominantly away from the equator, supporting the existence of an equatorial source region. There are exceptions and one event, observed 3° from the equator, also showed some propagation back to the equator with equal energy. Four periodic wave packets were seen in another event. This event showed unidirectional propagation away from the equator over all packets with periodicity approximately one‐half of the calculated time for a typical bouncing wave packet. Consequently, the periodicity is not the signature of a classical periodic structured Pc 1–2 pulsation event of the type seen on the ground. Generally, the results for these waves with f < fHe+ may be interpreted by assuming an ion cyclotron instability source located near the equator and irregularly emitting wave trains of energy into one or both hemispheres, with minimal reflection at the ionosphere.
Published Version
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