HR: 1340h
AN: SM23A-0488    [Abstracts]
TI: Latitude-independent Pc5 Geomagnetic Pulsations Associated With Field Line Resonance
AU: * Sung, S
EM: sksung@spacelab.khu.ac.kr
AF: Department of Astronomy and Space Science, Kyung Hee University, Yongin, Kyunggi, 449-701 Korea, Republic of
AU: Kim, K
EM: khan@khu.ac.kr
AF: Department of Astronomy and Space Science, Kyung Hee University, Yongin, Kyunggi, 449-701 Korea, Republic of
AU: Lee, D
EM: dhlee@khu.ac.kr
AF: Department of Astronomy and Space Science, Kyung Hee University, Yongin, Kyunggi, 449-701 Korea, Republic of
AU: Cattell, C A
EM: cattell@belka.space.umn.edu
AF: School of Physics and Astronomy, University of Minnesota, 116 Church Street, S.E., Minneapolis, MN 55455 United States
AU: Andre, M
EM: ma@irfu.se
AF: Swedish Institute of Space Physics, Uppsala Division, Box 537, Uppsala, SE 751 21 Sweden
AU: Khotyaintsev, Y V
EM: yuri@irfu.se
AF: Swedish Institute of Space Physics, Uppsala Division, Box 537, Uppsala, SE 751 21 Sweden
AB: The latitude-independent Pc5 pulsations with a spectral peak at $\sim$2.8 mHz were observed with IMAGE and SAMNET magnetometer array in the morning sector (0700-1000 local time) on April 29 (Day 119), 2001. The spectral amplitude had a local peak at $\sim$67$\deg$ geomagnetic latitude, where a sudden phase change of $\sim$180$\deg$ appeared. A vortical equivalent ionospheric current structure centered at latitude between 67$\deg$ and 71$\deg$ was observed during the Pc5 pulsations and the rotational sense of the current vortex was reversed for one cycle of the pulsation. During the interval of the enhancement of the Pc5 pulsations, the POLAR spacecraft in the morning side crossed near the magnetic shell (L $\sim$ 8) corresponding to the latitude where the spectral amplitude was maximum, and observed $\sim$2.8 mHz pulsations in the radial electric field and compressional magnetic field components. Since the toroidal mode Alfv\'{e}n waves in the magnetosphere are characterized by an electric field perturbation in the radial direction, the simultaneous presence of the pulsations in both components indicates that a field line resonance (FLR) was driven by compressional Pc5 pulsations. Using solar wind data, we conformed that the compressional Pc5 pulsations at POLAR occurred during an interval of enhanced solar wind dynamic pressure. From the analysis of the ground magnetometer data and POLAR data, we suggest that latitude independent ground magnetic perturbations are caused by the vortical equivalent current generated by FLR-associated field-aligned currents.
DE: 2409 Current systems (2708)
DE: 2700 MAGNETOSPHERIC PHYSICS
DE: 2752 MHD waves and instabilities
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting