Whistler Wave-driven Variation Of Distribution Function Of Energetic Particles In Earth’s Radiation Belts

Radiation belts surrounding Earth region as captured geomagnetic energetic charged(200keV-100MeV)particles is one of the important regions of Earth’s magnetosphere.The main source of high-energy particles is the solar wind particles captured by the Earth’s magnetic field,which move back and forth between the two magnetic mirror points of the radiation belts.Radiation belt around the earth was tread-like distribution,divided into inner radiation belt and outer radiation belt.with high energy density in the middle of the region is the groove area.Charged particles constitute the radiation belts have three adiabatic invariants,there can be a longer period of time.High energy particles will change the status of spacecraft electronic components,resulting in spacecraft abnormal operation,but also lead to astronauts health damage.This poses a serious security challenge for the national space program.The violent disturbance of the geomagnetic field produces a strong ground potential that threatens the safety of the power grid and the oil pipeline.Therefore,to study and predict the outer radiation belt energetic electrons dynamical evolution is significant.Previous theoretical studies have shown that the observed chorus waves could accelerate the high-energy electrons with gyro-resonance interaction,and dayside chorus can produce butterfly distribution of energetic electrons in the Earth’ s radiation belts by preferentially accelerating medium pitch angle electrons,but this requires the further confirmation from high-resolution satellite observation.We study the evolution of relativistic electron fluxes(1.8-2.6 MeV)in the outer radiation belt during the strong geomagnetic storm March 17 to 18,2013 using Van Allen Probes observations.The relativistic electron flux increased by 50-100 times during the recovery phase,and Van Allen Probes simultaneously observed nightside chorus waves were enhanced around the location L = 4.1.Meanwhile,we study the evolution of relativistic electron fluxes(1.8-3.4 MeV)in the outer radiation belt during the strong geomagnetic storm January 20,2016 using Van Allen Probes observations.The relativistic electron flux increased by 10 times during the recovery phase,and Van Allen Probes simultaneously observed dayside chorus waves were enhanced around the location L=5.We calculated the bounce-averaged resonant electron diffusion coefficients with Gaussian distributions and a dipole geomagnetic field model.We estimate the evolution of relativistic electron phase space density through Fokker-Planck diffusion equation solution.The Numerical simulations indicate that the observed chorus waves could accelerate the high-energy electrons with gyro-resonance interaction.Meanwhile,we report correlated Van Allen Probes data on wave and particle during the 11-13 April 2014 geomagnetic storm.We find that a butterfly pitch angle distribution of relativistic electrons is formed around the location L = 4.52,corresponding to the presence of enhanced dayside chorus.The Numerical simulations indicate that acceleration by dayside chorus can yield the electron flux evolution both in the energy and butterfly pitch angle distribution,providing a further evidence for the formation of butterfly distribution of relativistic electrons driven by electromagnetic waves.