Statistical study of the storm time radiation belt evolution during Van Allen Probes era: CME- versus CIR-driven storms

Coronal mass ejection (CME)-driven or corotating interaction region (CIR)-driven storms can change the electron distributions in the radiation belt dramatically, which can in turn affect the spacecraft in this region or induce geomagnetic effects. The Van Allen Probes twin spacecraft, launched on 30 August 2012, orbit near the equatorial plane and across a wide range of L with apogee at 5.8R(E) and perigee at 620 km. Electron data from Van Allen Probes MagEIS and REPT instruments have been binned every 6h at L = 3 (defined as 2.5 < L < 3.5), 4 (3.5 < L < 4.5), 5 (4.5 < L < 5.5). The superposed epoch analysis shows that (1) CME storms induce more electron flux enhancement at L = 3 for energy channels below 1MeV than CIR storms; (2) CME storms induce more electron flux enhancement at L = 4 and 5 in the energy channels above 1MeV than CIR storms; (3) CIR storms induce more electron flux enhancement at L = 4 and 5 in the energy channels below 1MeV than CME storms; (4) intense CME induce more than 50 times flux enhancement for the energy channel around 400keV at L = 3; (5) intense CIR induce more than 50 times flux enhancement for the energy channel around 200 keV at L = 4. These results are consistent with a general picture of enhanced convection over a longer period for CIR storms which increased flux closer to geosynchronous orbit consistent with earlier studies, while CME storms likely produce deeper penetration of enhanced flux and local heating which is greater at higher energies at lower L*.