Inter-Calibration Between the Electron Flux Measurements of FengYun-3B and Van Allen Probe-A Based on Electron Phase Space Density Conjunctions

Cross-satellite calibration of energetic particle fluxes is essential to understanding Earth's radiation belt dynamics and modeling the space radiation environment. Using the method of comparing phase space density (PSD) conjunctions in the same set of phase space coordinates, we perform a cross-satellite calibration of energetic electron fluxes measured by the Low Earth Orbit Chinese FengYun-3B satellite (FY-3B) and the near-equatorial Highly Eccentric Orbit Van Allen Probe-A (VAP-A), respectively. VAP-A provides pitch angle resolved electron (directional) differential fluxes while FY-3B provides omnidirectional electron differential fluxes. Before calculating the PSDs from FY-3B high energy electron detector (HEED), a method is introduced to estimate the local pitch angle of FY-3B based on the installation direction information of HEED and the T89c magnetic field model. We calculate the calibration factors by using the PSD conjunctions inferred from the two satellites for three fixed sets of (μ, K, L*) during the geomagnetic storm times. The calibration factors range from 0.76 to 0.86 varying with fixed sets of (μ, K, L*), which indicates that the electron differential fluxes from FY-3B are higher than that from VAP-A. During geomagnetic quiet times, we perform calibration by using independent Gaussian fitting analysis of the number of points with the unaveraged PSDs of FY-3B and VAP-A for three fixed sets of (μ, K, L*), with the corresponding calibration factors of 0.78, 0.72, and 0.46. The calibrated electron differential fluxes of FY-3B measured at the high magnetic latitudes, can be used in the future modeling of the radiation belt electron dynamics.