Dayside reconnected field lines in the south-dusk near-tail flank during an IMF By >0 dominated period

M. Fujimoto, T. Mukai, A. Matsuoka, A. Nishida, T. Terasawa, K. Seki, H. Hayakawa, T. Yamamoto, S. Kokubun, and R. P. Lepping

Department of Earth and Planetary Science, Tokyo Institute of Technology, Tokyo, Japan


A prolonged period of By > 0 dominated IMF conditions was monitored by WIND on Dec., 18-19, 1994. Observations on convection over the southern polar cap in the middle of this period (IMF Bz ~ 0) were available from AKEBONO. Detection of the well-known dawn-to-dusk flow observing simultaneously energy-dispersed ions in the cusp strongly indicates that the field lines reconnected at the dayside were azimuthally accelerated. GEOTAIL happened to be in the duskside flank at (XGSM, ZGSM) ~ (-15 ~ -23, -1 ~ -7)RE. The GEOTAIL data not only prove that this near-tail flank region in the southern hemisphere is filled with azimuthally accelerated flux tubs that are loaded with solar wind plasma, but they also show that O+ ions are transported tailward along these field lines. The latter is a new finding which suggests a route for transporting O+ ions from the ionosphere to the magnetotail.

Geophys. Res. Lett., 24, 931-934, 1997