Probing the auroral acceleration region through ISR inversion
Abstract
The power source for the aurora is known to be a Poynting flux carried by Earthward directed Alfven waves originating in the distant equatorial magnetosphere. The attenuation of this electromagnetic (EM) power in the ionosphere produces elevated ion temperatures in ionospheric E-region, which can be directly sensed by incoherent scatter radar (ISR). At altitudes of 2-3 Re above the discrete aurora, some of this EM flux is converted to electron kinetic energy (KE) flux through plasma processes that remain poorly understood. The attenuation of this KE flux in the ionosphere produces plasma density enhancements over an altitude range of ~80-300 km, which are also directly sensed by ISR. Using an appropriate forward model for the ionospheric response, ISR measurements of plasma temperature and density may be inverted to provide estimates of the causative magnetospheric power source (KE or EM) on a given flux tube. When this procedure is applied to time- dependent ISR measurements across an active auroral boundary, a unique tool emerges for investigating time- dependent energy conversion in the near-Earth magnetosphere. This paper describes a formalism for applying ISR inversion in the study of the auroral acceleration. Examples from both the Sondrestrom and the Poker Flat ISR (PFISR) facilities are presented.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFMSA51B0516C
- Keywords:
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- 2451 Particle acceleration;
- 2483 Wave/particle interactions (7867);
- 2494 Instruments and techniques;
- 2700 MAGNETOSPHERIC PHYSICS (6939);
- 2712 Electric fields (2411)