Drift-bounce resonance between charged particles and ultralow frequency waves: theory and observations

Abstract:

Ultralow frequency waves are known to be able to resonate with charged particles through their drift and bounce motions. Most research interest has focused on the resonance with drift motion, which can accelerate charged particles to very high energies. The role of the bounce motion, especially for those particles with lower energies, has attracted less attention. Here we start from the general theory of wave-particle interactions, to predict the characteristic signature of drift-bounce resonance, which in the pitch angular spectrum can be described by the superposition of 180-deg phase shifts at conjugated pitch angles over a series of inclined stripes. This signature differs from previous predictions, and after validated by real observations, provides new insights into the picture of magnetospheric wave-particle interactions.