Structure of Earth's outer radiation belt inferred from long‐term electron flux dynamics

This is the authors' abstract. We don't add key points for this paper.

We map the spatial structure of the electron belts over their radial range (L = 1–11 RE) using a total of 25 years of observations by NASA, ISAS, and GPS spacecraft. Correlation analysis reveals significant radial structuring of the outer belt and identifies three regions, while earlier single‐spacecraft studies are used to interpret the results. The central region P1 (L = 4.1–7.5 RE) has a well‐known slow response (2–3 days) most probably due to shear‐hydrodynamic effects of the interplanetary medium, which excite ULF waves at low latitudes. In the innermost region P0 (L = 3.0–4.1 RE) the electron response is rapid (<1 day). It appears related to solar wind ram‐hydrodynamic inputs (compressions) and/or time‐varying interplanetary electric and magnetic fields. Region P2 (L > 7.5 RE) has a much weaker brief response to magnetic field orientation and low interplanetary plasma velocities, anticorrelated with the other two regions. The findings and, in addition, the solar‐cycle modulation of the region size strongly suggest that the solar wind excites nonlinear response modes in the inner magnetosphere which are prototypically revealed in the three regions. Given this spatial variability, the optimal approach to next‐generation modeling and electron storm forecasting may differ considerably for each region.