HR: 14:30h
AN: SH42D-04    [PDF]
TI: Coronal Magnetic Diagnostics With FASR
AU: * White, S M
EM: white@astro.umd.edu
AF: Department of Astronomy, University of Maryland, College Park, MD 20742
AU: Gary, D E
EM: dgary@njit.edu
AF: Dept. of Physics, New Jersey Inst. of Technology 323 King Blvd, Newark, NJ 07102
AU: Lee, J
EM: jlee@njit.edu
AF: Dept. of Physics, New Jersey Inst. of Technology 323 King Blvd, Newark, NJ 07102
AU: Giordano, G
EM: giordano@njit.edu
AF: Dept. of Physics, New Jersey Inst. of Technology 323 King Blvd, Newark, NJ 07102
AB: Coronal magnetography is one of the main scientific drivers for the proposed Frequency Agile Solar Radiotelescope (FASR). Radio emission is particularly valuable as a diagnostic of coronal magnetic fields because (a) the emission mechanisms all depend on magnetic field, and (b) typical values of the electron gyroresonance frequency f\_B for coronal field strengths lie in the radio domain. The microwave emission from active regions is dominated by thermal gyroresonance emission at low harmonics of f\_B and this provides a well-understood diagnostic. Since f\_B is proportional to magnetic field strength, there is a simple mapping between frequency and magnetic field. A wide range of coronal magnetic field strengths can be sampled by observing across a wide range of radio frequencies simultaneously, and FASR is designed to do this quickly enough to follow changes in coronal fields. We demonstrate the ability to measure coronal fields with this technique by simulating a FASR observation of a realistic three-dimensional model of an active region and then determining the coronal magnetic field at the base of the corona from the simulated images. Comparison with radio images of gyroresonance emission from active regions is also a valuable tool for assessing extrapolations of surface magnetic field measurements into the corona, and we discuss several applications of this comparison. Gyrosynchrotron radio emission from nonthermal electrons accelerated by solar flares also can reveal the magnetic topology of the flare source and we discuss this briefly.
DE: 7509 Corona
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting