Resonant wave-particle interactions and the dynamics of Earth’s space radiation environment
Date and time:
Friday, April 25, 2014 - 3:00pm
The outer zone of the Van Allen radiation belts consists of highly energetic (MeV) electrons trapped in electromagnetic drifts encircling the Earth. The radiation belts are largely field-aligned structures ordered by Earth’s intrinsic dipole magnetic field, with equatorial crossing distances of approximately 3-7 Earth radii. This region of space is of particular significance due to the large number of spacecraft operating at these altitudes, and global society’s increasing reliance on space-based platforms for communications, navigation, weather prediction, and a variety of other economic and geopolitical purposes.
In this work we examine the resonant interaction of energetic radiation belt electrons with the dynamic electric and magnetic fields that govern the evolution of the near-Earth space radiation environment. We discuss the particle transport and energization within the belts that results from drift-resonant interaction with large-scale, low-frequency fluctuations in the geomagnetic field, and contrast these effects with those due to ‘local heating’, whereby radiation belt electrons are accelerated in place via resonant interactions with higher frequency electromagnetic waves common in Earth’s magnetosphere. We discuss the use of global magnetohydrodynamic (MHD) models to gain insight into the fundamental wave characteristics governing stochastic transport processes in the radiation belts, and review recent results from the NASA Van Allen Probes mission providing observational evidence of the range of resonant wave-particle interactions driving radiation belt activity.