A New Discovery of Critical Features Governing Earth's Radiation Belt Enhancement

This paper reports on a new discovery of critical features of radiation belt relativistic electron enhancement. Close tracking of detailed electron flux evolution recorded in the Van Allen Probes data reveals that regardless of magnetic storm strength, relativistic electron intensities do not increase gradually or continuously, but instead mostly (if not entirely) increase abruptly and intermittently, undergoing a series of discrete, fast (~1s-10s min timescales) flux increases that often appear as brief step-like jumps. Each discrete, brief increase sharply turns on and off with magnetic field dipolarization. Furthermore, it can occur simultaneously at ~10s keV to MeV energies, with the inner boundary of enhancement region locating further out with increasing energy, consistent with the energy-dependent injection boundary. This newly uncovered features, which cannot be explained by local wave acceleration or radial diffusion, provide convincing evidence that impulsive radial transport associated with strong substorm dipolarization is most likely the primary driver for radiation belt enhancement.