"Earth's Radiation Belt Electron Acceleration and Its Response to Solar Wind Drivers"

Wen Li (Department of Astronomy/Center for Space Physics, Boston University)

Earth’s Van Allen radiation belts, which extend from ~1,000 to ~60,000 km above the Earth’s surface, are the region where highly relativistic particles reside. In the collisionless radiation belt environment, wave-particle interaction is a fundamental physical process in transferring energy and momentum between particles with different species and energies. The extremely dynamical evolution of the radiation belt electrons is caused by various solar wind drivers and thus understanding the Sun’s influence on the radiation belt electrons is critical in forecasting space weather, which has broad impacts on our technological systems and society.

This talk will focus on discussing two of the most important and outstanding problems in radiation belt science, that is (1) how tens of keV plasmasheet electrons are accelerated to ultra-relativistic energies (multiple MeV) and (2) which solar wind conditions lead to such efficient electron acceleration. Over the past few decades, local acceleration driven by whistler-mode chorus waves and inward radial diffusion have been proposed to be important to drive efficient radiation belt electron acceleration. However, the quantitative role of each physical process has not been clearly identified yet. In this talk, I will show how I use realistic global distribution of whistler-mode chorus waves obtained from an innovative technique to simulate the dynamical electron evolution, and determine the primary electron acceleration mechanism by comparing against the Van Allen Probes electron observation. Through analyzing a number of electron acceleration events observed by the Van Allen Probes, I further evaluate solar wind drivers leading to ultrarelativistic electron acceleration in the Earth’s radiation belt, which is critical in predicting space weather using the upstream solar wind conditions.