On the heating of the outer radiation belt to produce high fluxes of relativistic electrons: Measured heating rates at geosynchronous orbit for high-speed stream-driven storms

Abstract

electron radiation belt at geosynchronous orbit is determined for the interval from 36 to 72 h after the onset of high-speed stream-driven storms. Multisatellite measurements of the radiation belt temperature are used for 93 high-speed stream-driven storms. During the storms, the outer electron radiation belt temperature changes from ∼120 keV to ∼190 keV. The average heating rate of 32 keV d-1 is obtained. The heating rate during the storms is found to be positively correlated with the solar wind velocity and with the Kp index of geomagnetic activity and to be negatively correlated with the solar wind number density. When the solar wind velocity is held fixed, the correlation of the heating rate with Kp vanishes. Expressions for the change in the heating rate as function of the solar wind speed, the solar wind density, and the Kp index are fit to the data. The heating rate is uncorrelated with the amplitude of magnetic field fluctuations in the magnetosphere. Correlations between the heating rate and the level of velocity, density, and magnetic field fluctuations in the magnetosphere and in the solar wind are weaker than the correlations of the heating rate with the solar wind velocity and density. The heating rates correspond to a kinetic energy density change of 3.6 × 10-11 erg cm-3 d-1 at geosynchronous orbit, to a specific entropy change of 4.1 × 106 eV cm2 d-1 at geosynchronous orbit, and to a total heating rate of the geosynchronous orbit region of 5.3 × 106 Watts. Copyright 2010 by the American Geophysical Union.