HR: 08:15h
AN: SH31A-02    [Abstracts]
TI: Faraday Rotation Measurements Over Three Cassini Solar Conjunctions
AU: * Jensen, E A
EM: ejensen@igpp.ucla.edu
AF: UCLA, IGPP UCLA Box 951567, Los Angeles, CA 90095 United States
AU: Iess, L
EM: iess@hermes.ing.uniroma1.it
AF: Uni Roma "La Sapienza", Dipt IAA Uni Roma "La Sapienza" Via Eudossiana, 18, Roma, 00184 Italy
AU: Asmar, S W
EM: sami.asmar@jpl.nasa.gov
AF: JPL, RSSG JPL, Pasadena, CA 91109 United States
AU: Bird, M K
EM: mbird@astro.uni-bonn.de
AF: Uni Bonn, Radioastronomisches Institut Uni Bonn Auf dem Hgel 71, Bonn, D-53121 Germany
AU: Luhmann, J G
EM: jgluhmann@sunspot.ssl.berkeley.edu
AF: UC-Berkeley, Space Science Laboratory UC-Berkeley Grizzly Peak Blvd. at Centennial, Berkeley, CA 94720 United States
AU: Russell, C T
EM: ctrussell@igpp.ucla.edu
AF: UCLA, IGPP UCLA Box 951567, Los Angeles, CA 90095 United States
AB: We use radio science data collected from the solar coronal occultation of the Cassini spacecraft in 2002, 2003 and 2005 to measure Faraday rotation. Faraday rotation is the rotation observed in the plane of polarization of an EM wave passing through a magnetized medium. It is proportional to the integrated product of the electron density and the background magnetic field parallel to the radio frequency wave vector. We compare the Faraday rotation measurements to our model; our model combines the Tyler et al. (1976) electron density model and a Potential Field Source Surface model using Wilcox Solar Observatory spherical harmonic coefficients. We find that our Faraday rotation model resembles the steady background measurements. Notable events during the experiments include streamers, waves, and CMEs crossing the line of sight. In 2002 the closest approach of the signal to the surface of the sun was 0.75 solar radii; the closest approach was closer in 2003 (0.5 Rs) and again in 2005 (0.16 Rs). Our Faraday rotation model includes the option of a constant-alpha force-free flux rope intersecting the line of sight. Notable Faraday rotation behavior has been reproduced with this model including the disturbance displacing the measurements either entirely above or below the background Faraday rotation and the characteristic 'W' signature. We discuss the variables contributing to the behavior including intersecting colatitude and longitude angles, size, velocity, expansion, and twist.
DE: 6900 RADIO SCIENCE
DE: 7500 SOLAR PHYSICS, ASTROPHYSICS, AND ASTRONOMY
DE: 7509 Corona
DE: 7513 Coronal mass ejections (2101)
DE: 7524 Magnetic fields
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005