HR: 10:20h
AN: SM22A-01    [Abstracts]
TI: Multipoint Observations of Pi2 pulsations During Substorm Recovery
AU: Liou, K
EM: kan.liou@jhuapl.edu
AF: Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099 United States
AU: Yumoto, K
EM: yumoto@geo.kyushu-u.ac.jp
AF: Space and Earth Electromagnetism Laboratory, Department of Earth and Planetary Sciences, Kyushu University , 6-10-1 Hakozaki, Fukuoka, 812-8581 Japan
AU: Mukai, T
EM: mukai@stp.isas.jaxa.jp
AF: ISAS, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, 229-8510 Japan
AU: Nagai, T
EM: nagai@geo.titech.ac.jp
AF: Dept Earth & Planetary Sciences, Tokyo Inst Technology, 2-12-1 Ookayama, Tokyo, 152-8551 Japan
AB: Pi2 pulsations are usually discussed in relation to the expansion phase onset of magnetospheric substorms. Pulsations in the Pi2 band are observed at other times but the wave mode and excitation mechanism of these quiet-time Pi2 pulsations have not been identified. In this paper we examine Pi2 pulsations observed during the recovery phase of a substorm, 1300-1600 UT, January 7, 1997. The pulsations occurred as the auroral luminosity, measured by the UVI experiment on the Polar satellite, steadily declined. What is remarkable is that pulsations in the Pi2 band were present continuously. In the last hour of the 3-hour period the overall intensity of the aurora became very low (less than 1 GW) and no localized intensification of aurora is discernible in individual UVI images. The properties of the pulsations, as observed at mid- to low-latitude ground stations on the nightside, are similar to those of Pi2 pulsations associated with substorm expansions. Pulsations in the Pi2 band were also observed on the dayside. The Geotail spacecraft was located at (-30, -5, 3) Re GSE, in the plasma sheet near the Sun-Earth line, but it did not detect strong plasma flows. The observed properties of the Pi2 pulsations suggest that they originated from the same oscillation mode as usual Pi2 pulsations, but the stimulation mechanism of the mode is yet to be identified.
DE: 2704 Auroral phenomena (2407)
DE: 2752 MHD waves and instabilities
DE: 2768 Plasmasphere
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting