April 27, 2012, 12:00 pm - 1:00 pm

April 27, 12:00 pm - 1:00 pm

Effects of Nonlinear Wave-Particle Interactions on Electron dynamics in the Magnetosphere

Dr. Qiuhua Zheng, NASA Goddard Space Flight Center/University of Maryland

Non-linear wave-particle interaction in the magnetosphere has significant contribution to Earth’s radiation belt dynamics but is still missing in current radiation belt models. Previous studies of non-linear wave effects mainly focused on the energy changes of an electron passing through a plasma wave region, thus covering only a fraction of the electron’s single-trip trajectory between its two mirror points. We have developed a test particle code which enables us to study the cumulative non-linear wave effects over multiple electron bounce periods. We found that non-linear wave-particle interactions are rather common with the presence of chorus waves. The non-linear wave effects take the form of energy advection, which can accelerate electrons rather efficiently. However, energy advection is often accompanied by electron pitch angle advection, causing electron pitch angles to decrease and constraining electron energy advection. We will also demonstrate that the chorus wave plays an important role in the formation of electron storm-time butterfly pitch-angle distribution. The test particle approach can be used to estimate both linear and nonlinear transport coefficients in the global radiation belt models.