2. Instrumentation and Datasets
The Van Allen Probes, launched in August 2012, consist of two identical satellites and operate in almost same orbits with perigees of ~600 km, inclination of ~10°, apogees of ~5.8 Earth radii (RE) and spin period of ~11s (Mauk et al., 2012). The Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instrument onboard the Van Allen Probes, which are designed to obtain a comprehensive physical understanding of ring current, provides measurements of protons in the energy range of ~7 - 600 keV (Mitchell et al., 2013). The level 3-PAP data with pitch angle information are adopted in this study. Due to the high-voltage issues during the early phase of the emission of RBSPICE-A, we only adopted the data from RBSPICE-B in the present study (Summers et al., 2017). The L shell used in this study is McIlwain L calculated with IGRF and OP77Q (Olson and Pfitzer, 1982) magnetic field model.