HR: 0800h
AN: SH21A-0286    [Abstracts]
TI: Alfven Profile in the Lower Corona: Implications for Shock Formation
AU: * Evans, R M
EM: revansa@gmu.edu
AF: George Mason University, 4400 University Drive MSN 3F3, Fairfax, VA 22030, United States
AU: Opher, M
EM: mopher@physics.gmu.edu
AF: George Mason University, 4400 University Drive MSN 3F3, Fairfax, VA 22030, United States
AU: Manchester, W B
EM: chipm@umich.edu
AF: Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109, United States
AU: Velli, M
EM: marco.velli@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, South Pasadena, CA 91109, United States
AU: Gombosi, T I
EM: tamas@umich.edu
AF: Center for Space Environment Modeling, University of Michigan, 1517 Space Research Buildings, Ann Arbor, MI 48109, United States
AB: Recent events (e.g. Tylka et al. 2005) indicate that CME-driven shocks can form at 1-3 solar radii and are responsible for the GeV/nucleon energies observed in some ground level solar energetic particle events. The formation of shocks depends crucially on the background solar wind environment, in particular on the profile of the background Alfvén speed in the corona. Significant strides have been made in the effort to develop realistic models of CME events; however, there is no consensus as to the profile of the Alfvén speed in the lower corona. Here we provide an overview of ten state-of-the-art models, which includes various methods to model magnetic field and density, as well as different strategies for accelerating the solar wind. We present the Alfvén speed profile for each model in the lower corona. We find that the "valley" and "hump" structures anticipated by Mann et al. (2003) are sometimes present, but in some models the Alfvén profiles drop off quickly. We discuss the implications of these profiles, such as whether it will allow a shock to form, dissipate, and form again (i.e. multiple shocks). Our study indicates that it is crucial to establish the Alfvén speed as a function of height before determining if shocks can form in the lower corona.
DE: 7509 Corona
DE: 7959 Models
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Fall Meeting