Midtail plasma flows and the relationship to near-Earth substorm activity: A case study
- Univ. of Maryland, College Park, MD (United States)
- Los Alamos National Lab., NM (United States)
- Abastumani Astrophysical Lab., Tibilisi (Georgia)
Recent simulations of magnetotail reconnection have pointed to a link between plasma flows, dipolarization, and the substorm current wedge. In particular, Hesse and Birn have proposed that earthward jetting of plasma from the reconnection region transports flux into the near-Earth region. At the inner edge of the plasma sheet this flux piles up, producing a dipolarization of the magnetic field. The vorticity produced by the east-west deflection of the flow at the inner edge of the plasma sheet gives rise to field-aligned currents that have region 1 polarity. Thus in this scenario the earthward flow from the reconnection region produces the dipolarization and the current wedge in a self-consistent fashion. Here the authors examine observations made on April 8, 1995 by the Active Magnetospheric Particle Tracer Explorers/Ion Release Module (IRM), the geosynchronous satellites 1979-053, 1983-019, and 1984-037, and Syowa station, as well as AE. This event is unique because IRM was located near the neutral sheet in the midnight sector for an extended period of time. Ground data show that there was ongoing activity in the IRM local time sector for several hours, beginning at 1800 UT and reaching a crescendo at 2300 UT. This activity was also accompanied by energetic particle variations, including injections, at geosynchronous orbit in the nighttime sector. Significantly, there were no fast flows at the neutral sheet until the great intensification of activity at 2300 UT. At that time, IRM recorded fast earthward flow simultaneous with a dipolarization of the magnetic field. Since the later stages of this event support Hesse and Birn, it is argued that the physics of substorms is not exclusively rooted in the development of a global tearing mode. Processes at the inner edge of cross-tail current that cause a disruption of the current and a consequent dipolarization and current wedge may be unrelated to the formation of a macroscale reconnection region. 40 refs., 6 figs.
- OSTI ID:
- 91330
- Journal Information:
- Journal of Geophysical Research, Vol. 99, Issue A12; Other Information: PBD: 1 Dec 1994
- Country of Publication:
- United States
- Language:
- English
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