HR: 09:10h
AN: SH51D-05 [Abstracts]
TI: Sheaths: A Comparison of Magnetospheric, ICME, and Heliospheric Sheaths
AU: * Richardson, J D
EM: jdr@space.mit.edu
AF: M.I.T., MIT 37-655, Cambridge, MA 02139, United States
AU: Sibeck, D G
EM: dsibeck@pop600.gsfc.nasa.gov
AF: NASA GSFC, Greenbelt Rd., Greenbelt, MD 20771, United States
AU: Liu, Y
EM: liuxying@space.mit.edu
AF: M.I.T., MIT 37-655, Cambridge, MA 02139, United States
AB:
When a supersonic flow encounters an obstacles, shocks form to
divert the flow around the obstacle. The region between the
shock and the obstacle is the sheath, where the supersonic flow is
compressed, heated, decelerated, and deflected. Supersonic flows,
obstacles, and thus sheaths are observed on many scales throughout
the Universe. We compare three examples seen in the heliosphere,
illustrating the
interaction of the solar wind with obstacles of three very different
scales lengths. Magnetosheaths form behind planetary bow shocks
on scales ranging from tens to 100 planetary radii. ICME sheath
form behind shocks driven by solar disturbances on scale lengths of
a few to tens of AU. The heliosheath forms behind the termination
shock due to the obstacle presented by the interstellar medium on
scale lengths of tens to a hundred AU.
Despite this range in scales some
common features have been observed. Magnetic holes, possibly due to
mirror mode waves, have been observed in all three of these sheaths.
Plasma depletion layers are observed in planetary and ICME sheaths. Other
features observed in some sheaths are wave activity (ion cyclotron, plasma),
energetic particles, transmission of Alfven waves/shocks, tangential discontinuities
turbulence behind quasi-parallel shocks, standing slow mode waves, and
reconnection on the obstacle boundary. We
compare these sheath regions, discussing similarities and differences and
how these may relate to the scale lengths of these regions.
DE: 2101 Coronal mass ejections (7513)
DE: 2111 Ejecta, driver gases, and magnetic clouds
DE: 2126 Heliosphere/interstellar medium interactions
DE: 2154 Planetary bow shocks
DE: 2728 Magnetosheath
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Joint Assembly