The temporal evolution of electron distributions and associated wave activity following substorm injections in the inner magnetosphere

The temporal evolution of electron distributions and associated wave activi ty following substorm injections in the inner magnetosphere are investigate d using data from the CRRES satellite. Equatorial electron distributions an d concomitant wave spectra outside the plasmapause on the nightside of the Earth are studied as a function of time since injection determined from the auroral-electrojet index (AE). The electron cyclotron harmonic (ECH) wave amplitudes are shown to be very sensitive to small modeling errors in the l ocation of the magnetic equator. They are best understood at the ECH equato r, defined by the local, maximum in the ECH wave activity in the vicinity o f the nominal magnetic equator, suggesting that the ECH equator is a better measure of the location of the true equator. Strong ECH and whistler mode wave amplitudes are associated with the injected distributions and at the E CH equator, in the region 6.0 less than or equal to L < 7.0, exponential fi ts reveal wave amplitude decay time constants of 6.3+/-1.2 and 4.6+/-0.7 ho urs, respectively. Pancake electron distributions are seen to develop from injected distributions that are nearly isotropic in velocity space and, in this region, are seen to form on a similar timescale of approximately 4 hou rs suggesting that both wave types are involved in their production. The ti mescale for pancake production and wave decay is comparable with the averag e time interval between substorm events so that the wave-particle interacti ons are almost continually present in this region leading to a continual su pply of electrons to power the diffuse aurora. In the region 3.8 less than or equal to L < 6.0 the timescale for wave decay at the ECH equator is 2.3 +/- 0.6 and 1.1 +/- 0.2 hours for ECH waves and whistler mode waves respect ively, although the pancakes in this region show no clear evolution as a fu nction of time.