Dynamic mechanisms of rapid dropout in the outer radiation belt observed after the Coronal Mass Ejection associated with Shock in July 2016

Abstract:

The decrease of relativistic electron flux in the outer radiation belt is observed after the Coronal Mass Ejection (CME) associated with shock reach the Earth’s magnetosphere in July 19, 2016. The magnetopause standoff distance is calculated through the solar wind parameters, reaching approximately 5 Re, and the efficiency of magnetopause shadowing mechanism during the loss particles to outer magnetosphere is estimated. When solar structures, such as CMEs, reach the Earth’s magnetosphere it may occur disturbances in several magnetospheric plasma parameters resulting on the excitation of waves over a wide range of frequencies. In this work we are interested in the frequencies ranges from hundreds of Hz up to about 10 kHz - Chorus waves, and from 2 mHz up to about 7mHz - Ultra Low Frequency - ULF waves. The lower band chorus waves (~ hundred of Hz) are detected in July 19-20, 2016, which is favorable to contribute with rapid dropout observed. The ULF waves activities are detected, and the Power Spectral Density - PSD is strong at the beginning of the July 20. The compressional and poloidal polarization modes are preferential during the dropout, which may contribute with the significant values of the radial diffusion coefficient, consequently may contribute with loss particles to outer magnetosphere. Therefore, the wave-particle interactions are estimated with focus in the pitch angle scattering mechanism by Chorus waves, and the drift resonance mechanism by ULF waves. We investigate the efficiency of each dynamic mechanisms during this rapid dropout observed in the outer radiation belt.