Statistics and Empirical Models of the Plasmasphere Boundaries From the Van Allen Probes for Radiation Belt Physics

Abstract

We deduce the electron plasma density from the NASA Van Allen Probes Electric Field and Waves and Electric and Magnetic Field Instrument Suite and Integrated Science measurements and extract the plasmasphere boundaries throughout 2012–2019. We use the gradient method for locating the plasmapause at Lpp and the 100 cm−3 density threshold for the plasmasphere outer edge at L100. We show how, where, and when both Lpp and L100 coincide when the plasmapause gradient exists. L100 is demonstrated to bound the plasmasphere at large L-shell in the dusk. The plasmasphere expands farther out than predicted from the Carpenter and Anderson (1992, https://doi.org/10.1029/91JA01548) model. We generate statistics of the plasmasphere boundaries binned by L-shell, magnetic local time (MLT), and geomagnetic indices, leading to new models for radiation belt codes. The L100 boundary commonly varies by ∼±0.5 L, increasing with activity up to ∼±1 L, becomes MLT-dependent for Kp > ∼2, and is preferentially steep on the night side for non-quiet times and a wider region in the afternoon sector.