HR: 0800h
AN: SM11A-1166    [Abstracts]
TI: Temperature Anisotropy Constraint In The Plasma Sheet
AU: * Lin, T
EM: ltf@bu.edu
AF: Boston University, Astronomy Department 725 Commonwealth Ave., Boston, MA 02215 United States
AU: Spence, H
EM: spence@bu.edu
AF: Boston University, Astronomy Department 725 Commonwealth Ave., Boston, MA 02215 United States
AU: Kepko, L
EM: lkepko@bu.edu
AF: Boston University, Astronomy Department 725 Commonwealth Ave., Boston, MA 02215 United States
AU: Gary, S P
EM: pgary@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop D466, Group ISR-1 Los Alamos National Laboratory , Los Alamos, NM 87545 United States
AU: Mukai, T
EM: mukai@stp.isas.jaxa.jp
AF: Institute of Space and Astronautical Science, Sagamihara, Kanagewa, Japan, Department of Space Plasma Physics, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai,Sagamihara, Kanagewa,229-8510,, Sagamihara, Kan 229-8510 Japan
AB: Geotail observations of proton temperature anisotropies in the magnetotail show a sharp upper bound at - 1 > 0 vs. where and // are directions in reference to ambient magnetic field and . The same upper bound has been observed in the magnetosheath, in the solar wind, and in the outer magnetosphere. Hybrid simulations have shown that this constraint is due to proton scattering by the electromagnetic proton cyclotron anisotropy instability. Our observations show a spread of three decades in domain and effectively extends previous results to high region. The bi-Maxwellian assumption is tested and found to be valid in high region while it breaks down in low regions, thus it holds in the plasma sheet, which is a necessary condition for above theory and simulations. For the opposite sense of proton temperature anisotropy, the upper bound of 1- > 0 vs. in = [1,10] domain is also shown; simulations predict that this constraint is due to scattering by the electromagnetic proton firehose instability. However, waves excited by these temperature anisotropies are often obscured by background fluctuations.
DE: 2471 Plasma waves and instabilities
DE: 2700 MAGNETOSPHERIC PHYSICS
DE: 2730 Magnetosphere--inner
DE: 2744 Magnetotail
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting