Relativistic electron microbursts associated with whistler chorus rising tone elements: GEMSIS-RBW simulations

摘要

Relativistic electron microbursts, which are bursty enhancements of the precipitation of relativistic electrons, are often observed by low-altitude satellite measurements. These microbursts are likely to play an important role in high-energy electron flux loss in the outer radiation belt. Some observations suggest that whistler chorus waves are a cause of relativistic electron microbursts. First, we derived the relativistic time of flight model considering the propagation of whistler mode waves, and then investigated characteristics of the precipitations. We found that relativistic electron precipitation has a positive energy dispersion at low altitude. The duration of electron precipitation by one whistler chorus element decreases when the energy of the precipitated electrons is increased. We then performed three-dimensional test particle simulation with a newly developed wave-particle interaction model using realistic plasma parameters in the inner magnetosphere. The test particle simulation showed for the first time that the resonant interactions with whistler chorus elements at high-latitudes produce bursty enhancements of relativistic electron precipitation, thus confirming the results of the TOF analysis. A few Hz modulations are embedded in the precipitating electron flux variations, which is associated with the repetition period of the whistler chorus elements. The simulation results indicate that microbursts of relativistic electrons of the outer belt are caused by chorus wave-particle interactions at high latitudes and a series of rising tone elements of chorus waves produce a few Hz modulation of microbursts observed by the SAMPEX satellite.