HR: 1330h
AN: SH53A-04    [Abstracts]
TI: Flux-Rope CME Geometry and its Relation to Observed CME Morphology
AU: * Krall, J
EM: krall@ppdmail.nrl.navy.mil
AF: Plasma Physics Division, Naval Research Laboratory, 4555 Overlook Ave., SW, Washington, DC 20375-5346 United States
AU: St. Cyr, O C
EM: Chris.StCyr@nasa.gov
AF: Solar Physics Branch, NASA-Goddard Space Flight Center, Greenbelt, MD 20771 United States
AU: St. Cyr, O C
EM: Chris.StCyr@nasa.gov
AF: Department of Physics, The Catholic University of America, Washington, DC 20064 United States
AU: Chen, J
EM: chen@ppdmail.nrl.navy.mil
AF: Plasma Physics Division, Naval Research Laboratory, 4555 Overlook Ave., SW, Washington, DC 20375-5346 United States
AB: Observed flux-rope CME morphology depends on the underlying flux-rope geometry and its observed projection onto the two-dimensional plane of the sky. We use a simple parameterization of a three-dimensional flux rope to determine a "typical model flux-rope geometry" that corresponds to the "average observed flux-rope coronal mass ejection (CME) morphology" as observed at a leading-edge (LE) height of about 5 solar radii (e.g., LASCO/C2). The model flux rope, the curved axis of which is assumed to trace out an ellipse, can be described in terms of eccentricity of the ellipse, the width (minor diameter) of the flux rope at the apex, and the height of the apex above the solar surface. At an LE height of 5 solar radii, the resulting morphology is only a weak function of the foot point separation. Assuming that flux-rope expansion is self-similar, we have only two model-geometry parameters: the eccentricity and the aspect ratio (apex height over apex width). For each given pair of model parameters, we consider an ensemble of possible orientations (latitude, longitude, and rotation about the vertical direction) each with a corresponding synthetic coronagraph image. These images are used to produce statistical measures of the morphology for comparison to statistical measures of observed flux-rope CME morphology. The model parameters that best fit the observations constitute a prediction of the underlying geometry (eccentricity and aspect ratio) of a typical flux-rope CME. When STEREO confirms this prediction, the flux-rope hypothesis will be further validated. Supported by ONR and NASA
DE: 7513 Coronal mass ejections
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2005 Joint Assembly