HR: 0800h
AN: SM51B-0528    [Abstracts]
TI: On the Plasma Sheet Boundary Layer and Bursty Bulk Flow Connection
AU: * Lennartsson, O
EM: lenn@spasci.com
AF: Lockheed Martin ATC, ADCS, B255, 3251 Hanover St, Palo Alto, CA 94304, United States
AB: What has for many years been referred to as the "plasma sheet boundary layer," or the PSBL, is proving not to be a near-planar high-latitude layer of continuous proton field-aligned flows, but a high-latitude region of recurring bursts of protons (and electrons) with time-dispersed thermal energies and narrow filamentary structures. This is evident from Polar and Cluster ion composition measurements made at 4 to 7 Earth radii (R_E) distance. As first implied by the Polar observations and later confirmed by the multipoint Cluster observations, these proton bursts have a transverse fine structure that may span but a few gyroradii of a 10-keV proton at these altitudes. The rate of energy dispersion varies a great deal, indicating a burst source that is more than 100 R_E down the tail at times, but may be inside of 20 R_E at other times. The latter is where most observations of earthward directed "bursty bulk flows" of protons, or BBFs, have been made near the equatorial plane. That there is a likely connection between the two kinds of proton flows is suggested by (1) the similarly bursty and structured nature of both and (2) the fact that the BBFs are invariably associated with a transient local increase of the northward tail B_z component, without an increase in the B_x; a process that probably allows the equatorial plasma to expand earthward along higher-latitude field lines. That this is indeed a plausible scenario is illustrated by Cluster magnetic field and ion data from about 19 R_E near local midnight in the equatorial plane.
DE: 2704 Auroral phenomena (2407)
DE: 2748 Magnetotail boundary layers
DE: 2760 Plasma convection (2463)
DE: 2764 Plasma sheet
DE: 2790 Substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting