Multipoint analysis of a bursty bulk flow event on April 11, 1985
- Johns Hopkins Univ., Laurel, MD (United States)
- Univ. of California, Los Angeles, CA (United States); and others
In an attempt to place short-lived, high-speed magnetotail flows termed bursty bulk flow events (BBFs) in the context of substorm phenomenology the authors analyze one such event that took place on April 11, 1985, using data from several spacecraft and many ground stations. The substorm onset, which took place at 0127 UT, had a meridian 2 hours of local time east of AMPTE/IRM. The satellite did not detect high-speed flows at that time. A high-latitude ({approx}70{degree} corrected geomagnetic) substorm intensification took place at 0202 UT centered {approx}0.5 hour of local time west of the AMPTE/IRM meridian. The ISEE 2 satellite at the magnetotail lobe and the LANL 019 satellite at geosynchronous altitude were both at the same meridian as AMPTE/IRM at the time. The 0202 UT substorm intensification was associated with (1) a dipolarization at the ISEE 2 satellite at 0200:30 UT, (2) a BBF onset at AMPTE/IRM at 0202 UT accompanied by an intense dipolarization consistent with current wedge formation, (3) an energetic particle injection at geosynchronous altitude that took place at 0204 UT. The plasma acceleration region associated with this substorm intensification was estimated to be {approx}8 R{sub E} tailward of AMPTE/IRM. The Earthward energy transport measured at AMPTE/IRM can account for the expected magnetospheric power consumption if the BBF has a cross-sectional area of only 1-2 R{sup 2}{sub E} in the Y-Z direction. The authors propose that the fast flows transport and pile up magnetic flux through a very narrow (a few R{sub E} in Y extent) flow channel in the midtail to the edge of an expanding dipolarization front in the near-Earth region. Unlike the near-Earth plasma sheet, which dipolarizes across many hours of local time, the midtail plasma sheet may exhibit longitudinally localized dipolarization. This may explain the often observed lack of one-to-one correlation between midtail activity and substorms.
- OSTI ID:
- 255058
- Journal Information:
- Journal of Geophysical Research, Vol. 101, Issue A3; Other Information: PBD: 1 Mar 1996
- Country of Publication:
- United States
- Language:
- English
Similar Records
Statistical characteristics of bursty bulk flow events
Statistical characteristics of bursty flow events