Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsm32a..04h&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #SM32A-04
Physics
[0310] Atmospheric Composition And Structure / Airglow And Aurora, [2435] Ionosphere / Ionospheric Disturbances, [2463] Ionosphere / Plasma Convection, [2475] Ionosphere / Polar Cap Ionosphere
Scientific paper
During a large magnetic storm on December 15, 2006, an unusually elongated, bright airglow plume, which is considered as an optical manifestation of polar cap tongue of ionization (TOI), was detected with an all-sky airglow imager (ASI) at Resolute Bay, Canada (74.73N, 265.07E). The absolute optical intensity of the airglow plume was greater than 500 R, which is much brighter than that of non-stormtime polar cap patches. This infers that the source of the plume was dayside mid-latitudes far away from the central polar cap. Two-dimensional imaging capability of the ASI well visualizes temporal evolution of the TOI plume, which was drifting dynamically in the central polar cap area, with a temporal resolution of 2 min. The optical data also show that some meso-scale structures (250-600 km) were embedded within the plume. In order to reveal the factors controlling the dynamic behavior of the optical TOI, we carried out comprehensive analysis of the plasma transport process from mid-latitude to polar cap by combining data from various instruments such as ASI, GPS-TEC, SuperDARN radars and LEO satellites. Simultaneous ion density measurement with the DMSP spacecraft strongly suggests that the plume was extending from the dayside as a narrow stream of dense plasma and thus is actually an optical manifestation of TOI. The DMSP and NOAA auroral particle observations demonstrate that the polar cap boundary abruptly expanded equatorward (toward 60 MLAT) just 1 hour before the appearance of the optical TOI. This extreme expansion allowed the anti-sunward convection to capture the daytime sunlit plasmas and deliver them deep into the polar cap as a luminous airglow plume. During this interval of extreme polar cap expansion, the mid-latitude SuperDARN radar in Hokkaido, Japan observed an enhanced anti-sunward plasma flow even in the region of close field lines (at around 58 MLAT). This flow on closed field lines also contributed to the transportation of the daytime sunlit plasmas to higher latitudes. Simultaneous GPS-TEC and DMSP driftmeter data suggest that the enhanced flow on closed field lines was associated with the subauroral polarization stream (SAPS) appearing in the duskside mid-latitude trough. By combining all the above observational results, dynamics of TOI is discussed in terms of abnormal plasma transport during a large magnetic storm.
Hairston Marc R.
Hosokawa Kazuo
Nishitani Nozomu
Ogawa Takuro
Otsuka Yoichi
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