HR: 0800h
AN: SH21A-0392    [Abstracts]
TI: Imaging of Interplanetary Disturbances Causing Forbush Decreases
AU: * Simnett, G
EM: gms@star.sr.bham.ac.uk
AF: School of Physics and Astronomy, University of Birmingham, Birmingham, B15 2TT United Kingdom
AU: Kahler, S
EM: stephen.kahler@hanscom.af.mil
AF: Air Force Research Laboratory, Space Vehicles Directorate, Hanscom AFB, MA 01731 United States
AB: Forbush decreases (FDs) are caused by interplanetary shocks and ejecta that shield the Earth from galactic cosmic rays. The solar origins of those ejecta can be observed as coronal mass ejections (CMEs) in coronagraphs, but their propagation through interplanetary space near or past the Earth has not been previously observable. The Solar Mass Ejection Imager (SMEI), launched into polar Earth orbit in January 2003, now allows us to search for the white light signatures of interplanetary CMEs (ICMEs) responsible for FDs. SMEI is unique in that it can monitor the progress of CMEs through the inner heliosphere out to distances beyond 1 AU, and distinguish those which hit the Earth from those that do not. We discuss SMEI observations of two ICMEs that resulted in both geomagnetic storms and FDs and of two ICMEs that may have been responsible for gradual FDs without accompanying geomagnetic disturbances. The SMEI observations provide information on the approximate spatial location and trajectories of large ICMEs that may result in FDs and hence can be useful as a space weather tool.
DE: 7513 Coronal mass ejections
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting