HR: 08:48h
AN: SM11B-04    [Abstracts]
TI: Comparing Different Models for Fast Earthward Flows in the Magnetotail: Moving Flux Ropes, Unsteady Reconnection, Pressure-Depleted Plasma Bubbles, and Atypical Currents Sheets
AU: * Sitnov, M I
EM: Mikhail.Sitnov@jhuapl.edu
AF: Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099, United States
AU: Runov, A V
EM: Andrei.Runov@oeaw.ac.at
AF: Space Research Institute, OEAW, Schmiedlstrasse 6, Graz, 8042, Austria
AU: Runov, A V
EM: Andrei.Runov@oeaw.ac.at
AF: Institute of Geophysics and Planetary Physics, UCLA, 3845 Slichter Hall, Los Angeles, CA 90095-1567, United States
AU: Ohtani, S
EM: Shin.Ohtani@jhuapl.edu
AF: Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099, United States
AB: The physics of fast earthward flows or BBFs, a major mechanism of bursty transfer of the plasma and magnetic flux in the terrestrial magnetotail, remains uncertain and controversial. A part of observations can be explained as signatures of earthward moving flux ropes or secondary plasmoids dragged by the earthward part a larger-scale reconnection region [Slavin et al., 2003]. The statistics of variations of the z-component of the magnetospheric magnetic field in the central plasma sheet [Ohtani et al., 2004] suggest no changes of the magnetic field topology for another group of BBFs. These observations can be explained as signatures of either unsteady reconnection, which remains located tailward of the spacecraft, or other phenomena that are connected but not identical to reconnection in its active phase. These are the plasma bubbles, flux tubes with the reduced specific entropy that may move earthward faster than the neighboring flux tubes due to the buoyancy force. However, the original model of bubbles arising from local reductions of the plasma pressure [Pontius and Wolf, 1990] also explains only a part of observations. Another part [Angelopoulos et al., 1992] reveals no reduction of the plasma pressure in BBFs. One more model, which explains both missing magnetic topology changes and no reduction of the plasma pressure [Sitnov et al., 2005] describes the bubble as a seam in the body of the tail plasma, which appears after the formation and tailward retreat of a small plasmoid, and which is composed of atypical, embedded and bifurcated thin current sheets. Signatures of such atypical current sheets have been convincingly demonstrated recently in CLUSTER observations [Runov et al., 2003]. In this presentation we elaborate the BBF models and compare them with 2001 and 2002 tail CLUSTER observations in the central plasma sheet. These include full-particle simulations of the secondary plasmoid formation in tail-like systems, two- and three- dimensional features and dynamical properties of atypical current sheets that constitute plasma bubbles. Comparison with data is focused on the distinction between plasma flows moving in the earthward part of a neutral line (which may be both stable and moving earthward or tailward) and similar motions of plasma and magnetic field structures associated with plasma bubbles.
DE: 2723 Magnetic reconnection (7526, 7835)
DE: 2744 Magnetotail
DE: 2760 Plasma convection (2463)
DE: 7859 Transport processes
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting