HR: 0800h
AN: SM11A-1164    [Abstracts]
TI: Modeling non-Harris Current Sheets to fit Tail Cluster Observations
AU: * Sitnov, M I
EM: sitnov@umd.edu
AF: Institute for Research in Electronics and Applied Physics, University of Maryland, Energy Research Facility (Bldg. #223), Paint Branch Drive, College Park, MD 20742-3511 United States
AU: Swisdak, M M
EM: swisdak@ppd.nrl.navy.mil
AF: Naval Research Laboratory, 4555 Overlook Ave SW, Code 6794, Washington, DC 20375 United States
AU: Guzdar, P N
EM: guzdar@glue.umd.edu
AF: Institute for Research in Electronics and Applied Physics, University of Maryland, Energy Research Facility (Bldg. #223), Paint Branch Drive, College Park, MD 20742-3511 United States
AU: Drake, J F
EM: drake@plasma.umd.edu
AF: Institute for Research in Electronics and Applied Physics, University of Maryland, Energy Research Facility (Bldg. #223), Paint Branch Drive, College Park, MD 20742-3511 United States
AB: Four-spacecraft Cluster mission provided for the first time an unambiguous spatial-temporal picture of thin current sheets in the tail of Earth's magnetosphere. Some new elements of this picture, such as bifurcated current sheets and their flapping motions, could not be explained by the former current sheet theory and simulations and strongly stimulated their further development. It becomes more and more clear, in particular, that the classical theory of the current sheet equilibrium proposed by Harris [1962], which was used for years in current sheet and reconnection studies, needs to be strongly generalized to fit the new observations. Here we present the new results on a generalized Harris theory, which explicitly takes into account the effects of plasma anisotropy and non-gyrotropy, as well as particle simulations based on the new family of current sheet equilibria. We explore in particular the structure of the ion pressure tensor and the distinctive features of the ion distribution function. We present a modification of the previous model of the bifurcated current sheet [Sitnov et al., 2003] with a very small plasma anisotropy outside the sheet. We show that in contrast to Harris-type models, the presence of a dawn-dusk magnetic field makes the new models asymmetric along the north-south direction. We also consider the features of anisotropic current sheet with the thickness less than the thermal ion gyroradius in the field outside the sheet, which are most relevant to 2003 tail Cluster observations. It is shown that the spatial equilibrium structure of such sheets is much less susceptible to the ion anisotropy as compared to the thicker sheets. On the other hand, different dynamics of ions and electrons in these super-thin anisotropic sheets result in their strong charging. Another interesting effect is a relatively quick further collapse of the super-thin sheets prior to their inflation and distortion in the form of kink-type flapping motions.
DE: 7827 Kinetic and MHD theory
DE: 7835 Magnetic reconnection
DE: 2744 Magnetotail
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting