A search for upstream pressure pulses associated with flux transfer events: An AMPTE/ISEE case study
- Los Alamos National Lab., NM (United States)
- Max-Planck-Institut fuer Extraterrestrische Physik, Garching-bei-Muenchen (Germany)
- Univ. of California, Berkeley, CA (United States)
- Technische Universitaet Braunschweig (Germany)
- NASA/Goddard Space Flight Center, Greenbelt, MD (United States)
On September 19, 1984, the Active Magnetospheric Particle Tracers Explorers (AMPTE) United Kingdom Satellite (UKS) and Ion Release Module (IRM) and ISEE 1 and 2 spacecraft passed outbound through the dayside magnetopause at about the same time. The AMPTE spacecraft pair crossed first and were in the near-subsolar magnetosheath for more than an hour. Meanwhile the ISEE pair, about 5 R{sub E} to the south, observed flux transfer event (FTE) signatures. The authors use the AMPTE UKS and IRM plasma and field observations of magnetosheath conditions directly upstream of the subsolar magnetopause to check whether pressure pulses are responsible for the FTE signatures seen at ISEE. Pulses in both the ion thermal pressure and the dynamic pressure are observed in the magnetosheath early on when IRM and UKS are close to the magnetopause, but not later. These large pulses appear to be related to reconnection going on at the magnetopause nearby. AMPTE magnetosheath data far from the magnetopause do not show a pressure pulse correlation with FTEs at ISEE. Moreover, the magnetic pressure and tension effects seen in the ISEE FTEs are much larger than any pressure effects seen in the magnetosheath. A superposed epoch analysis based on small-amplitude peaks in the AMPTE magnetosheath total static pressure (nkT + B{sup 2}/2{mu}{sub 0}) hint at some boundary effects, <5 nT peak-to-peak variations in the ISEE 1 and 2 B{sub N} signature starting about 1 min after the pressure peak epoch. However, these variations are much smaller than the standard deviations of the B{sub N} field component. Thus the evidence from this case study suggests that upstream magnetosheath pressure pulses do not give rise to FTEs, but may produce very small amplitude signatures in the magnetic field at the magnetopause. 19 refs., 8 figs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 68410
- Journal Information:
- Journal of Geophysical Research, Vol. 99, Issue A7; Other Information: PBD: 1 Jul 1994
- Country of Publication:
- United States
- Language:
- English
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