UARS particle environment monitor observations during the November 1993 storm: Auroral morphology, spectral characterization, and energy deposition

Autor: Brian J. Anderson, R. Link, G. Crowley, J. D. Winningham, C. A. Gurgiolo, D. L. Chenette, J. R. Sharber, R. W. Nightingale, E. E. Gaines, R. A. Frahm
Rok vydání: 1998
Předmět:
Zdroj: Journal of Geophysical Research: Space Physics. 103:26307-26322
ISSN: 0148-0227
DOI: 10.1029/98ja01287
Popis: During the major storm of November 3–11, 1993, the UARS particle environment monitor (PEM), in a 57° inclination, 585-km circular orbit, made measurements of energetic particles, X rays, and magnetic field perturbations in the midnight-dawn magnetic local time sector of the northern hemisphere and in the noon-evening sector of the southern hemisphere. X-ray images provide a global picture (∼20-min resolution) of the electron precipitation regions twice per 90-min orbit, which were used to study morphology during the main and recovery phases of the storm. Detailed examination of the precipitating electrons measured between 5 eV and 5 MeV show that in the several hundred eV to several MeV energy range the spectra may often be represented by the kappa distribution, which has a thermal character in the keV range and a power law distribution at higher energies. Selected spectral measurements were used to calculate ionization production rates as functions of altitude. The profiles peak between 95 and 120 km, each having a secondary ledge at lower altitudes produced by the bremsstrahlung X rays. We show that the ionization thus produced can be significant at altitudes as low as the upper stratosphere. Because of the length of time over which this ionization is produced globally, it is expected to have a substantial impact on atmospheric chemistry. Global power inputs to the auroral regions due to precipitating particles have been computed for each day of the storm using PEM X-ray and particle observations. On November 4, 1993, the day that includes the main and early recovery phases of the storm, the northern hemispheric power calculated by in situ measurement of the electron fluxes was 56.8 GW; that determined by using the X-ray images was 47.4 GW, These values may be compared with the northern hemisphere Joule heating rate of 290 GW on the same day computed using the PEM magnetometer and electron flux measurements.
Databáze: OpenAIRE
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