Abstract:
The Van Allen Probes have observed both symmetric and asymmetric bipolar electric field
structures in the Earth's inner magnetosphere. In general, the symmetric bipolar structures are identified
as electron-phase space holes, whereas the asymmetric structures are interpreted as electron acoustic
double layers (EADLs). The generation mechanism of these EADLs is not entirely understood yet.We have
modeled the EADLs observed on 13 November 2012 by Van Allen Probe-B.We performed a fluid
simulation of the EADLs and tracked their formation and evolution in the simulation.We found that the
localized depletion and enhancement in the electron populations act as a perturbation to excite the
symmetric bipolar electron acoustic solitary waves, which later evolve into the EADLs. The Ponderomotive
force is found to be the main driver behind transformation of the symmetric electron acoustic solitary
waves to EADLs via formation of the electron acoustic shocks.
