Total electron and proton energy input during auroral substorms: Remote sensing with IMAGE-FUV

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Read Full Article (file size: 609663 bytes) Cited by JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. A8, 1183, doi:10.1029/2001JA009229, 2002 Total electron and proton energy input during auroral substorms: Remote sensing with IMAGE-FUV B. Hubert Laboratoire de Physique Atmosphérique et Planétaire, Université de Liège, Liège-Ougrée, Belgium J.-C. Gérard Laboratoire de Physique Atmosphérique et Planétaire, Université de Liège, Liège-Ougrée, Belgium D. S. Evans NOAA Space Environment Center, Boulder, Colorado, USA M. Meurant Laboratoire de Physique Atmosphérique et Planétaire, Université de Liège, Liège-Ougrée, Belgium S. B. Mende Space Sciences Laboratory, University of California, Berkeley, California, USA H. U. Frey Space Sciences Laboratory, University of California, Berkeley, California, USA T. J. Immel Space Sciences Laboratory, University of California, Berkeley, California, USA Abstract The IMAGE satellite carries three FUV imagers observing N₂ LBH, O I 1356 Å, and HI Lyman α emissions in the polar aurora. These simultaneous observations are used to characterize the precipitating electron and proton energy fluxes. The proton energy flux is derived from the Lyman α measurements on the basis of efficiency curves calculated with a Monte Carlo simulation of the proton aurora. The resulting proton contribution to the N₂ LBH and O I 1356 Å emissions is calculated and subtracted to obtain the electron contribution in the other two channels. These two quantities are used to determine the precipitating electron average energy and energy flux. The proton and electron energy fluxes are integrated over the hemisphere to obtain the rate of auroral energy dissipation (hemispheric power) carried by the protons and electrons separately. The time development of the proton and electron aurora during four winter time events is examined. Although the onsets of the proton and electron aurora coincide in time and space, the time of the peak of energy dissipation and the recovery time are often found to differ. The fractional energy flux carried by the protons is highest during quiet periods and reaches a minimum during the most active phase of the substorms. This result is in agreement with the dependence of the fractional proton hemispheric power on magnetic activity measured by NOAA 15. The hemispheric power deduced from the FUV images is compared to the NOAA-deduced values and found to be in reasonable agreement. Sources of uncertainties in the determination of the hemispheric power are discussed on the basis of several sensitivity tests. In particular, it is found that the most critical factor is the assumption made on the energy of the auroral protons if this energy is <25 keV. Published 14 August 2002. Index Terms: 0358 Atmospheric Composition and Structure: Thermosphere—energy deposition; 0310 Atmospheric Composition and Structure: Airglow and aurora; 2716 Magnetospheric Physics: Energetic particles, precipitating; 2788 Magnetospheric Physics: Storms and substorms. Read Full Article (file size: 609663 bytes) Cited by Citation: Hubert, B., J.-C. Gérard, D. S. Evans, M. Meurant, S. B. Mende, H. U. Frey, and T. J. Immel (2002), Total electron and proton energy input during auroral substorms: Remote sensing with IMAGE-FUV, J. Geophys. Res., 107(A8), 1183, doi:10.1029/2001JA009229. Copyright 2002 by the American Geophysical Union.

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