Plasma flow and magnetic field characteristics near the midtail neutral sheet
- Nagoya Univ., Aichi (Japan)
- NASA Goddard Space Flight Center, Greenbelt, MD (United States)
- Johns Hopkins Univ., Laurel, MD (United States)
- Univ. of California, Los Angeles, CA (United States)
- Los Alamos National Lab., NM (United States)
Using IMP 6, 7, and 8 magnetic field and plasma data, the authors have determined statistical occurrence properties of bulk flow and magnetic field orientation near the midtail neutral sheet. Characteristics of bulk plasma flow and magnetic field significantly change according to the radial distance down the tail. High-speed flow events (V>300 km/s) are essentially restricted to the region tailward of X = {minus}25 R{sub E} and are predominantly sunward or tailward. The low-speed flows were nearly equally likely to be in any direction, with the occurrence rate of duskward and sunward flow being larger than that of tailward and dawnward flow. Duskward flow occurrence is highest in the region Earthward of X = {minus}25 R {sub E}, while sunward flow occurrence is highest in the region tailward of X = {minus}25 R{sub E}. The significance of the dawn-to-dusk flow in the near-Earth region obtained in this study supports the idea that there exists a very effective mechanism to accelerate ions in the dawn-to-dusk direction and hence the relief of pressure buildup in the near-Earth region. During high-speed flow events the relationship between B{sub Z} polarity and plasma flow direction is largely consistent with that expected from the magnetic reconnection processes associated with substorms. There are also significant numbers of negative B{sub Z} events that are not associated with tailward flow. Mechanisms other than substorm neutral line should therefore also be taken into account to explain general B{sub Z} polarity in the midtail region. 40 refs., 9 figs.
- OSTI ID:
- 91333
- Journal Information:
- Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A12 Vol. 99; ISSN JGREA2; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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