HR: 0800h
AN: SH41B-02    [Abstracts]
TI: Accretion not Diversion One way ICME-sheaths differ from planetary magnetosheaths
AU: * Siscoe, G L
EM: siscoe@bu.edu
AF: Boston University, Center for Space Physics 725 Commonwealth Ave, Boston, MA 02215, United States
AU: Owens, M J
EM: mjowens@bu.edu
AF: Boston University, Center for Space Physics 725 Commonwealth Ave, Boston, MA 02215, United States
AU: Hughes, W J
EM: hughes@bu.edu
AF: Boston University, Center for Space Physics 725 Commonwealth Ave, Boston, MA 02215, United States
AU: Isenberg, P A
EM: phil.isenberg@unh.edu
AF: University of New Hampshire, Institute for the Study of Earth, Oceans, and Space, Durham, NH 03824, United States
AU: Odstrcil, D
EM: Dusan.Odstrcil@noaa.gov
AF: Space Environment Center, 325 Broadway, Boulder, CO 80305, United States
AB: ICME-sheaths differ from planetary magnetosheaths in that in a planetary magnetosheath, the solar wind flows around the planet, whereas in an ICME-sheath it piles up with little flow-around. We refer to the two types of sheaths as accretion type (ICME) and diversion type (planetary). That planetary magnetosheaths are of the diversion type is well known, but that ICME-sheaths are largely (though not totally) of the accretion type is newly recognized. We verify the statement using MHD simulations of solar wind flows in Earth's magnetosheath and in an ICME-sheath showing that the flow-around speed in the magnetosheath is about twice that in the ICME sheath. The simulations also show that the standoff distance between the shock and the body, normalized to radius of curvature, is also about twice as large in the magnetosheath as in the ICME-sheath. This result is confirmed by an analytical model. The two results - smaller flow-around speed and smaller flow-through distance in the ICME-sheath - imply that the solar wind mostly piles up in front of the ICME instead of flowing around it as it moves outward.
DE: 2101 Coronal mass ejections (7513)
DE: 2728 Magnetosheath
DE: 7513 Coronal mass ejections (2101)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Joint Assembly