Observations of high-speed plasma flow near the earth's magnetopause: evidence for reconnection
In an attempt to confirm the evidence for reconnection reported by Paschmann et al. (1979), we have examined three-dimensional plasma velocity distributions sampled near the magnetopause by using the LEPEDEA plasma instrument. During the magnetopause crossing of September 8, 1978, we observe high-speed flow in the magnetospheric boundary layer that is suggestive of the accelerated flow predicted by reconnection models. However, our low-energy plasma observations reveal an apparent inconsistency with the tangential stress balance condition, and there is no clear evidence available from the plasma measurements for a local, normal component v/sub n/. Simultaneous measurements of > or =45-keV energetic electrons show pancake-shaped pitch angle distributions and intensity variations that suggest a closed field line regime, whereas the high-speed plasma flow is predicted to occur on open field lines for the reconnection hypothesis. Allowing for finite gyroradius effects, the energetic particles show no signature of traversing from a closed to an open field line regime upon entering the boundary layer which contains high-speed ion flow. Since the energetic particle angular distributions indicate that the high-speed plasma flow occurs partly or entirely on closed field lines, we suggest that the simplest hypothesis is to place the entire boundary layer observed during this crossing on closed field lines. We find that several detailed features of the available measurements can be explained readily in this way. Our ISEE observations appear to be most consistent with inpulsive injection of magnetosheath plasma across the magnetopause in a process that involves both MHD and plasma kinetic instabilities.
- Research Organization:
- The Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242
- OSTI ID:
- 5023900
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 87:A4
- Country of Publication:
- United States
- Language:
- English
Similar Records
Three-dimensional plasma observations near the outer magnetospheric boundary
Three-dimensional plasma observations near the outer magnetospheric boundary. Report for 1977-1979
Related Subjects
GENERAL PHYSICS
MAGNETOPAUSE
PLASMA DRIFT
DISTRIBUTION FUNCTIONS
IONS
KEV RANGE 10-100
MAGNETIC FIELD CONFIGURATIONS
THREE-DIMENSIONAL CALCULATIONS
TRAPPING
CHARGED PARTICLES
ENERGY RANGE
FUNCTIONS
KEV RANGE
640203* - Atmospheric Physics- Magnetospheric Phenomena- (-1987)