Physics
Scientific paper
Dec 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003agufmsm51c0537t&link_type=abstract
American Geophysical Union, Fall Meeting 2003, abstract #SM51C-0537
Physics
2704 Auroral Phenomena (2407), 2768 Plasmasphere
Scientific paper
As part of the CRL-UAF cooperative middle atmosphere project, monochromatic imaging observations of aurora and airglow have been carried out at Poker Flat since October 2000. Monochromatic images are obtained every 5 minutes using two all-sky imagers at 10 emission lines. From these data, a new type of aurora which is stationary on the sky with some patch structures was found in the magnetic evening sector by Kubota et al. [2003]. The stationary characteristic suggests that this type of aurora corotates with the Earth. We have investigated this type of aurora in detail using 47 events identified in the period from October 2000 to April 2003. The motion of this type of aurora is not always corotating. Sometimes it drifts slowly. Considering this point, we call this type of aurora 'Quasi-Corotating (QC) aurora' here. QC aurora occurred on geomagnetic quiet conditions (Kp=0-3+) and mainly in the evening local time sector. From the DMSP/SSJ data, it is identified that precipitating electrons with energies of a few keV are the source of QC aurora, and that precipitating ions make no contribution to this type of aurora. We examined the source region of QC aurora in the magnetosphere using the LANL satellite data. The footprints of the LANL 1989-046 and 1991-080 are in the field of view of our imagers. It is found that the source region is usually located inside the plasmasphere. By comparing the aurora image data with the LANL particle data during the October 27, 2000 event, it is found that the aurora started to drift westward around 1800 MLT when the LANL satellite entered the plasma sheet region. Further we calculated the flow vectors representing the quasi-stationary motions of individual patches in aurora using the maximum cross-correlation method. In the case of the October 27, 2000 event, corotation flows are seen in the early evening sector of 1500-1600 MLT on the equatorial-plane in the magnetosphere (L=5-8). The flow speed becomes faster than the corotation speed after 1700 MLT and earthward flows become dominant around 1800 MLT. In the case of the December 6, 2001 event, corotation flows are seen around 1700 MLT at L=6-7 and its speed becomes less than the corotation speed around 1700 MLT like stagnation flows. Then, sunward flows become dominant after 1730 MLT outside L=7. It is suggested that the motions of the stationary or quasi-stationary patches reflect the fine structure of electric field potential near the plasmapause. Thus, it is possible to monitor the fine structures of magnetospheric convection near the plasmapause using this type of aurora.
Fukunishi Hiroshi
Kataoka Ryuho
Kubota Masahisa
Miyoshi Yasunobu
Murayama Yuko
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