HR: 10:50h
AN: SM42A-03    [Abstracts]
TI: Seasonal Variations of the Intensities of Large-scale Field-aligned Currents
AU: Higuchi, T
EM: higuchi@ism.ac.jp
AF: Institute of Statistical Mathematics , 4-6-7 Minami-Azabu Minato-ku, Tokyo, 106-8569 Japan
AU: * Ohtani, S
EM: ohtani@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723-6099 United States
AU: Ueno, G
EM: gen@ism.ac.jp
AF: Institute of Statistical Mathematics , 4-6-7 Minami-Azabu Minato-ku, Tokyo, 106-8569 Japan
AU: Kawano, H
EM: hkawano@geo.kyushu-u.ac.jp
AF: Kyushu University, Dept. Earth & Planetary Sciences , 6-10-1 Hakozaki Higashi-ku, Fukuoka, 812-8581 Japan
AB: In this study we examine seasonal variations of the intensities of large-scale field-aligned currents (FACs) with a focus on their dependence on the dipole orientation. The study is based on ~185,000 FAC crossings we identified from nearly 19 years_Eworth of magnetic field data from DMSP-F7 and F12-15 spacecraft. It is found that the average dayside FAC intensity is larger in the summer hemisphere than in the winter hemisphere by a factor of 2-3. This is consistent with the results of previous studies, and it can be attributed to the annual variation of the ionospheric conductance. It is also found that the annual variation of the dayside R2 current intensity is smaller in amplitude than that of the dayside R1 current intensity. In contrast, the annual variation of the nightside FAC intensity is complicated, which will be examined in more detail in terms of the ionospheric condition at the footpoints of FACs. It is also inferred from the dependence on the dipole clock angle that the FAC tends to be more intense around the equinoxes than around the solstices, which is inferred to reflect the fact that geomagnetic activity tends to be higher around the equinoxes.
DE: 2704 Auroral phenomena (2407)
DE: 2708 Current systems (2409)
DE: 2736 Magnetosphere/ionosphere interactions
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting