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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, A12217, doi:10.1029/2004JA010986, 2005

Overlap of the plasmasphere and ring current: Relation to subauroral ionospheric heating

C. Gurgiolo

Bitterroot Basic Research, Hamilton, Montana, USA


B. R. Sandel

Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA


J. D. Perez

Physics Department, Auburn University, Auburn, Alabama, USA


D. G. Mitchell

John Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA


C. J. Pollock

Southwest Research Institute, San Antonio, Texas, USA


B. A. Larsen

Department of Physics, Montana State University, Bozeman, Montana, USA


Abstract

The overlap of the ring current with the outer plasmasphere is thought to play a major role in storm-time related increases in the subauroral ambient topside electron temperature. Instabilities generated within the overlap region, Coulomb collisions of plasmaspheric electrons with the ring current ions, and charge exchange are all thought to work either individually or together to generate a downward heat flux into the ionosphere to produce the increase in temperature. Analysis of IMAGE two-dimensional ring current and plasmasphere density maps together with in situ DMSP ambient electron temperature data shows that the heating generally occurs over a small radial extent within the plasmasphere/ring current overlap region and may be significantly earthward of the plasmapause. This argues against collisional heat conduction as the source of the heat flux and for an instability-based process. The finding that the heating occurs within well-defined ratios of the cold plasmasphere to hot ring current density strengthens this supposition.

Received 20 December 2004; accepted 5 October 2005; published 16 December 2005.

Keywords: plasmasphere; ring current; ionosphere temperature; EMIC waves.

Index Terms: 2768 Magnetospheric Physics: Plasmasphere; 2778 Magnetospheric Physics: Ring current; 2467 Ionosphere: Plasma temperature and density.

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Citation: Gurgiolo, C., B. R. Sandel, J. D. Perez, D. G. Mitchell, C. J. Pollock, and B. A. Larsen (2005), Overlap of the plasmasphere and ring current: Relation to subauroral ionospheric heating, J. Geophys. Res., 110, A12217, doi:10.1029/2004JA010986.