HR: 1340h
AN: SH23A-1147    [Abstracts]
TI: Low Frequency Wave Aspect of Density Holes
AU: * Lin, N
EM: nlin@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California at Berkely, Berkeley, CA 94720, United States
AU: Lee, E S
EM: eslee@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California at Berkely, Berkeley, CA 94720, United States
AU: Parks, G K
EM: parks@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California at Berkely, Berkeley, CA 94720, United States
AU: Mozer, F
EM: fmozer@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California at Berkely, Berkeley, CA 94720, United States
AU: Wilber, M
EM: wilber@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California at Berkely, Berkeley, CA 94720, United States
AU: Lucek, E
EM: e.lucek@imperial.ac.uk
AF: Space and Atmospheric Physics, Imperial College, Imperial College, London, SW7 2BZ, United Kingdom
AU: Reme, H
EM: Henri.Reme@cesr.fr
AF: CESR, 9 ave du Colonel Roche, Toulouse, 31028, France
AB: The formation of density holes involves non-linear steepening of magnetic field and plasma density, which results in shock-like boundaries followed by a drop in both density and magnetic field. In this study we present the low frequency wave properties of density holes. The propagation properties of the waves, especially the upstream edges of the structure, have been studied using Cluster's four point observations. They include the phase velocities in the spacecraft and plasma rest frames, propagation directions and polarization. We have analyzed two events in great detail. They show that for these events, the structures are convected with the solar wind, and the phase speed in the plasma frame is much larger than the Alfven velocity. The waves are mostly circularly polarized in the left hand sense. The phase velocities calculated from four spacecraft timing analysis are compared with the velocity estimated from dE/dB. Their agreement shows the waves are electromagnetic. The steepening is most likely due to nonlinear steepening of ion cyclotron waves.
DE: 2149 MHD waves and turbulence (2752, 6050, 7836)
DE: 7839 Nonlinear phenomena (4400, 6944)
DE: 7851 Shock waves (4455)
DE: 7867 Wave/particle interactions (2483, 6984)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Fall Meeting