Observations of relativistic electron microbursts in association with VLF chorus

The Solar, Anomalous and Magnetospheric Particle Explorer (SAMPEX) satellit e frequently observes relativistic (>1 MeV) electron precipitation in the r adiation belts at L shells of 4-6 with bursty temporal structure lasting <1 s. This phenomenon can occur at all local times but is most often seen bet ween 0200 and 1000 magnetic local time. VLF chorus is also observed to occu r preferentially at these same local times. Using electron observations fro m the SAMPEX satellite Heavy Ion Large Telescope and data from the Polar sa tellite plasma wave instrument, we show correlation between observations of relativistic electron microbursts and VLF chorus with frequencies <2 kHz. In addition, the duration of the individual rising frequency chorus element s is comparable to the duration of the relativistic electron microbursts. I t has been speculated that relativistic electron microbursts are caused by wave-particle interactions, which strongly scatter electrons into the loss cone for a short period. Lower-energy electron microbursts in the range fro m tens to hundreds of keV have long been associated with chorus waves, sinc e these lower-energy electrons can resonate at the equator with whistler-mo de waves at chorus frequencies. Electrons of MeV energies do not satisfy th e first-order cyclotron resonance condition with chorus wave frequencies at the equator. However, MeV electrons may interact with chorus through highe r-order resonances or off-equatorial interactions.