A Statistical Look at the Radiation Belt Seed Population
Tuesday, 16 December 2014
One of the key goals of the Van Allen Probes mission is to understand the acceleration of the core radiation belt electron population (electrons with energy > 1 MeV). One important piece of this acceleration process are the 100's of keV seed electrons that originate as lower energy electrons in the plasma sheet, are transported into the inner magnetosphere and can be then be accelerated via wave-particle interactions to higher energies. The instrumentation of the Van Allen Probes mission offers an opportunity to make clear, simultaneous observations of both the seed and core populations in the heart of the radiation belts. These observations will allow us to better understand the role the seed population plays in the acceleration process and quantify the acceleration timescales. Here, we calculate phase space density (PSD) for nearly 18 months of observations from both the Magnetic Electron Ion Spectrometer (MagEIS) and Relativistic Electron Proton Telescope (REPT) instruments. Looking at fixed second invariant K and third invariant L* we examine how the electron PSD evolves for different values of first invariant μ (or equivalently energy). We are then able to clearly identify enhancements in the seed and core populations. For all the events in this 18 month time period, we quantify how well correlated enhancements to the core population are to enhancements to the seed population and what the acceleration timescales are as a function of energy.