Shock-Auroras: The Manifestation of Solar Wind-Magnetosphere-Ionosphere Interactions
Abstract
Although shock-auroras occur in the ionosphere, they represent the outer magnetospheric dynamics and interactions between the solar wind and the magnetosphere and the ionosphere. From a big picture of view based on the UV remote sensing from space, shock-auroras are characterized by a prompt response in seconds to the impingement of interplanetary shocks/pressure pulses, an onset location near noon, and a followed fast anti-sunward propagation along the auroral oval to midnight in ~10 min. The ionospheric speed is very high at ~6-11 km/s, which is much faster than the typical auroral speed of < 1 km/s. Zooming into the auroral small-scale structure (i.e., the auroral form), imaging data from all-sky imagers on the ground unveiled shock-aurora forms to be red arcs in the east-west orientation sitting along the poleward boundary of the oval and diffuse auroras spreading in the southern sky adjacent to arcs. The red arcs responded to the shock impingement slower than the diffuse aurora and appeared to be very stable in the shape and location. The red arc brightness was dimmer than the green diffuse aurora during the time when the magnetosphere was very compressed. For a particular event, the low-latitude boundary of the cusp was eroded in a moderate rate. As a result, the meridional width of the cusp increased by a factor of 2 within ~10 min. The diffuse aurora moved toward noon and the intensity exceeded the red arcs that were at ~5 kR. Those signatures indicated occurrences of a low latitude magnetic reconnection and wave-particle interactions initiated by plasma instabilities near the equator where the maximum temperature anisotropy is generated due to shock impingements. In addition to reviewing recent shock-aurora results of remote sensing and in situ observations, how auroral forms are associated with particle acceleration mechanisms will be emphasized. We will also discuss remaining questions and challenges in the theory and measurement.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFMSM54B..05Z
- Keywords:
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- 2704 MAGNETOSPHERIC PHYSICS / Auroral phenomena;
- 2706 MAGNETOSPHERIC PHYSICS / Cusp;
- 2736 MAGNETOSPHERIC PHYSICS / Magnetosphere/ionosphere interactions;
- 2784 MAGNETOSPHERIC PHYSICS / Solar wind/magnetosphere interactions