Relationship Between Ground-based and In-situ Plasma Sheet Measurements of Convection Penetration

Details Relationship Between Ground-based and In-situ Plasma Sheet Measurements of Convection Penetration Relationship Between Ground-based and In-situ Plasma Sheet Measurements of Convection Penetration

Dec 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsm53d..04s&link_type=abstract

American Geophysical Union, Fall Meeting 2009, abstract #SM53D-04

Physics

[2723] Magnetospheric Physics / Magnetic Reconnection, [2736] Magnetospheric Physics / Magnetosphere/Ionosphere Interactions, [2744] Magnetospheric Physics / Magnetotail, [2760] Magnetospheric Physics / Plasma Convection

Scientific paper

Shortly after the discovery of bursty plasma sheet convection, a number of observational studies have suggested a link between earthward flow bursts observed near the midnight central plasma sheet and auroral intensifications at the polar cap boundary (“polar cap boundary intensifications” or PBIs) and the southward propagating aurora (“auroral streamers”). Three different stages are identified during the southward progression of the streamers. In the first stage there is a boundary brightening followed, often within a few minutes, by the start of the propagation of aurora in the southward direction. The second stage, which usually lasts up to ten minutes, consists of the propagation of the auroral streamer into the equatorward edge of the aurora. In the third stage, the arrival of the streamer to the equatorward edge of the oval coincides with the onset of a bright spot that can last for as long as 20 minutes. Bursty convection is observed in association with streamers most commonly during steady magnetospheric convection and substorm recovery, although it is also observed in general during periods of sustained geomagnetic activity. This investigation has two objectives. The first is to determine whether reconnection is enhanced concurrently with the PBIs and whether the duration of the enhancement coincides with the southward expansion of the auroral streamers. The second objective is to determine whether the enhanced tail reconnection is associated with penetration of under-dense flux tubes into near-Earth plasma sheet. Ground-based multi-spectral optical measurements and in-situ Geotail and THEMIS measurements in the plasma sheet during extended periods of southward IMF show the causal chain whereby PBIs are indeed the optical manifestation of reconnection intensifications that power, in some cases, the penetration of fast convection into the plasma sheet. Observations show, however, that there are also intense flow bursts (~ 1000 km/s) without any clear indication of streamers and streamers without a corresponding flow burst. We discuss the consequences of these apparent discrepancies on the paradigm of penetration of under-dense flux tubes in the plasma sheet.

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