Proton loss of inner radiation belt during geomagnetic storm of 2018 based on CSES satellite observation

The proton distribution in inner radiation belt is often affected by strong geomagnetic storm disturbance.Based on the data of the sun-synchronous CSES satellite,which carries with several high energy particle payloads and was launched in February 2018,we analyzed the extensive proton variations in the inner radiation belt in a wide energy range of 2 MeV-220 MeV during 2018 major geomagnetic storm.The result indicates that the loss mechanism of protons was energy dependence which is consistent with some previous studies.For protons at low energy 2 MeV-20 MeV,the fluxes were decreased during main phase of the storm and did not come back quickly during the recovery phase,which is likely to be caused by Coulomb collision due to neutral atmosphere density variation.At higher energy 30 MeV-100 MeV,it was confirmed that the magnetic field line curvature scattering plays a significant role in the proton loss phenomenon during this storm.At highest energies>100 MeV,the fluxes of protons kept a stable level and did not exhibit a significant loss during this storm.