UNUSUAL SATELLITE-ELECTRON SIGNATURE WITHIN THE URANIAN MAGNETOSPHEREAND ITS IMPLICATIONS REGARDING WHISTLER ELECTRON LOSS PROCESSES

It has been reported that during the outbound (nightside) portion of t he Voyager 2 encounter with the Uranian magnetosphere, intense whistle r mode emissions were observed near the magnetic equator (lambda(m) ap proximately 16-degrees-C) and at L shell values between approximately 5.5 and approximately 9 R(U). Comprehensive calculations of whistler-d riven pitch angle diffusion, in previous work, have yielded strong dif fusion electron lifetimes of approximately 1 hour for 20 to 40 keV ele ctrons. In this paper we report on an unusual and sharply defined char ged particle feature that: (1) involved electrons between 22 and 35 ke V, (2) was observed during the time period of the intense whistler mod e observations, (3) was aligned very accurately and sharply with the m inimum L shell position (L approximately 7.5) of the satellite Ariel, and (4) has an appearance that suggests that electrons were removed on ly at and beyond Ariel's minimum-L. On the basis of our conclusion tha t the signature was caused by electron interactions with either Ariel or materials distributed along Ariel's orbit, the signature could not have been generated for at least 10 hours prior to its observation. Th us the calculated whistler loss times are in apparent conflict with th e signature observation. A scenario of events is proposed to explain t he data that involves substormlike electron acceleration on the Urania n nightside and a subsequent sculpting of the electron spatial distrib utions via interactions with Ariel or materials distributed along Arie l's orbit. Interactions with distributed materials, such as micron-siz ed particulates, are favored because they minimize the discrepancy bet ween the whistler-loss calculations and the observations presented her e. The possibility exists that the accurate alignment of the sharp ele ctron feature with Ariel's minimum-L, and the absorptionlike character of the feature, are accidental, and that the feature is caused by dyn amical processes (e.g., substorms). In this case the dynamical process es must be quite dissimilar to those occurring in the Earth's magnetos phere.