HR: 0830h
AN: SH41B-0467    [PDF]
TI: A Simple Method for Determining the Time of Closest Approach to the Center of a Magnetic Fluxrope
AU: * Jensen, E A
EM: firerock@alum.mit.edu
AF: UCLA/IGPP, Slichter Bldg 595 Charles E. Young Dr., East, Los Angeles, CA 90095 United States
AB: A simple test can be used to determine {\em when} a spacecraft passing through a flux rope is closest to the center of that rope. The test consists of determining the angular change between successive magnetic field vectors as the spacecraft passes through the flux rope. Using a Bessel function model, it can be shown that the interior vectors rotate more slowly than the exterior vectors. Thus, the spacecraft is closest to the center of the rope where the angle between successive vectors is a minimum. This is consistent with our intuitive picture of a flux rope in which the exterior fields are tightly wound a round the axis and the central field is parallel to the rope axis. We show that this technique works for both stationary and expanding ropes. Finally, we examine the sensitivity of the technique to the impact parameter and noise in the magnetic field.
DE: 7513 Coronal mass ejections
DE: 7524 Magnetic fields
DE: 7819 Experimental and mathematical techniques
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting