Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufmsm12a0485t&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #SM12A-0485
Physics
0310 Airglow And Aurora, 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 (65.1N, 212.6E; 65.6 MLAT: MLT = UT-13 hours) since October 2000. Monochromatic images are obtained every 5 minutes using two all-sky imagers at 10 emission lines, i.e., HŸA (486.1 nm), OI (557.7 nm), N2+ (427.8 nm), background (572 nm), Na (589 nm), HŸA background (481 nm), OI (630.0 nm), OI (844.6 nm), OI (777.4 nm), and OI (630 nm). From these data, the new type of aurora which keeps its patch structure at some fixed location in the field of view was found in the magnetic evening sector by Kubota and Nagatsuma [2001]. These characteristics suggest that this type of aurora was corotating with the Earth. We have investigated the characteristics of such 'corotating aurora' in detail using 29 events identified in the period from October 2000 to April 2002. While imaging observation covers from 14 to 07 MLT, this type of aurora is observed only in the dusk to midnight sector (14 - 03 MLT). The aurora occurs on geomagnetic quiet conditions (Kp=0 - 3+) after the decay of substorm activity. The occurrence of this type of aurora are identified at emission lines, OI 557.7 nm, N2+ 427.8 and OI 844.6 nm, but not at OI 630.0 nm and HŸA 486.1 nm. This feature suggests that this type of aurora is excited by precipitating hard electrons. Precipitating electron and ion data obtained by DMSP/SSJ showed that the precipitating electrons with energies of few keV are the source of this aurora, and that precipitating ions are absent. Using simultaneous IMAGE/EUV (Extreme Ultraviolet Imager) data, we have examined the relationship between the corotating aurora mapped to the equatorial plane and the structure of the plasmasphere in three events observed on February 23, 24 and March 1, 2001. In these events it seems the plasmapause was unclear and the corotating aurora was mapped to the low plasma density region of ~102 /cm3. We have also studied the density structure of the plasmasphere from electron number densities estimated from the AKEBONO/PWS data obtained on October 27, 2000. In this event there is no sharp plasmapause, and the source region of the corotating aurora is mapped to the gradually decreasing low density region of the plasmasphere. Further data analysis using spacecraft and ground-based data will be performed to elucidate the generation mechanism of this type of aurora.
Fukunishi Hiroshi
Kubota Masahisa
Murayama Yuko
Toyoshima S.
Yoshida Naoki
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