Pitch angle diffusion of low‐energy electrons by whistler mode waves

The authors look at the question of precipitating electrons from the radiation belts. The common argument has been that pitch angle scattering of trapped electrons on whistler mode waves was the source of the precipitating electrons. As part of this theory there has been a threshold energy E[sub C] = B[sup 2]/2[mu][sub 0]N, the magnetic energy per particle which has been a threshold for this process. This energy is typically 10 keV. The observation of diffuse aurorae, as distinguished from distinct aurorae, was made in the 1970's. This is a rather weak and structureless ion and electron precipitation which extends around the auroral oval. The intensities are not inconsistent with pitch angle diffusion of plasma sheet electrons into the loss cone as being the source. The authors argue that there is no fundamental energy threshold for the whistler mode interactions, and therefore such scattering can account for the diffuse aurorae. They show theoretically that there is no reason why the characteristic energy E[sub C] should limit the energy of electrons participating in pitch angle diffusion from whistler waves. An additional consequence of this work is that experimental releases of lithium in the outer magnetosphere to stimulate increased precipitation or initiatemore » a magnetic substorm are not likely to succeed, consistent with CRRES lithium releases.« less