In-Situ Observations Of Landau Electron Trapping By Oblique Whistler Waves In The Outer Radiation Belt

Simultaneous observations of electron velocity distributions and oblique chorus waves by Van Allen Probe B are analyzed to identify long lasting (more than 6 hour) signatures of electron Landau resonant interactions with chorus waves in the radiation belts. The Landau resonant interactions became important for oblique whistler waves having a significant electric field component along the background magnetic field. Such interactions in the inhomogeneous magnetic field lead to parallel acceleration and to plateaus in the parallel (with respect to the background magnetic field) velocity component in the electron velocity distributions. We demonstrate that the observed electron energy related to the plateaus agrees with the energy required for resonant interaction with the simultaneously observed oblique whistler waves over a wide range of L-shells (from 3 to 6) in the outer radiation belt.