HR: 0800h
AN: SA21A-0270    [Abstracts]
TI: Global ionospheric disturbances during super magnetic storms
AU: * Huang, C
EM: cshuang@haystack.mit.edu
AF: MIT Haystack Observatory, Route 40, Westford, MA 01886 United States
AU: Foster, J
EM: jcf@haystack.mit.edu
AF: MIT Haystack Observatory, Route 40, Westford, MA 01886 United States
AU: Rideout, W
EM: wrideout@haystack.mit.edu
AF: MIT Haystack Observatory, Route 40, Westford, MA 01886 United States
AU: Zhang, Y
EM: yongliang.zhang@jhuapl.edu
AF: Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723 United States
AU: Paxton, L
EM: larry.paxton@jhuapl.edu
AF: Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723 United States
AB: Magnetic storms represent the largest disturbances in the magnetosphere and ionosphere. We will present the ionospheric observations by the Millstone Hill incoherent scatter radar, global GPS network, and TIMED GUVI instrument during two super storms. The sudden commencement (SSC) of the 15 July 2000 storm occurred at 19 UT, and the minimum Dst reached -301 nT. The dayside midlatitude ionospheric F region electron density showed a sudden decrease at Millstone Hill and Eglin in response to the SSC. The elevation scan measurements of the Millstone HIll radar show that the sudden decrease in the ionospheric electron density was related to an electron density trough which had an equatorward boundary at Eglin (magnetic latitude 41 degree) at 16 MLT. The formation of the trough may be related to equatorward incursion of the disturbance SAPS electric field. The dayside TEC decreased significantly at the equatorial and upper midlatitudes, and an enhanced TEC band occurred between the depleted regions. The SSC of the 29 October 2003 storm occurred at 07 UT, the storm was further enhanced at 18 UT, and the minimum Dst reached -363 nT. The Millstone Hill radar also detected a sudden decrease of the dayside F region electron density immediately after the storm enhancement. The simultaneous TIMED GUVI measurements show a significant decrease in the O/N2 ratio over the Atlantic sector from the auroral zone to anomaly latitudes, and large TEC depletions occurred coincidentally with the O/N2 decrease. In this second case, both the enhanced electric field and decrease of O/N2 ratio contributed to the depletion of the dayside midlatitude F-region electron density and TEC. The multiple measurements during the two storms reveal the distinct properties and mechanisms of the global ionospheric disturbances.
DE: 2431 Ionosphere/magnetosphere interactions (2736)
DE: 2435 Ionospheric disturbances
DE: 2441 Ionospheric storms (7949)
DE: 2730 Magnetosphere: inner
DE: 2788 Magnetic storms and substorms (7954)
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005