HR: 1330h
AN: SH42C-0551    [PDF]
TI: Propagation Effects on the Directivity Characteristics of Solar and Interplanetary Type II and Type III Radio Bursts
AU: * Golla, T
EM: golla@urap.gsfc.nasa.gov
AF: Department Of Astronomy, University of Maryland, College Park, MD 20742 United States
AU: MacDowall, R J
EM: macdowall@urap.gsfc.nasa.gov
AF: NASA, Goddard Space Flight Center, Greenbelt, MD 20771 United States
AB: Type II and type III radio bursts are excited by the CME driven shocks and flare accelerated electrons, respectively. These radio emissions contain advance information regarding the space weather critical CMEs and flare related particles. However, some uncertainities arise due to the dipole and quadrupole nature of the fundamental and second harmonic emission patterns of these bursts. For example, if the mode of emission is the second harmonic, it is less likely that the radio signals associated with the approaching CMEs or flare particles reach the observer if he/she is located in the nulls of the quadrupole. We will address this issue by (1) investigating the directivity patterns that arise from the conversion of Langmuir waves into radio emission at the fundamental and second harmonic of the electron plasma frequency in realistic situations especially including the weak magnetic fields, (2) determining the modifications to these emission patterns due to propagation effects by tracing the rays corresponding to the fundamental and second harmonic emission patterns in the presence of realistic density structures in the solar atmosphere; (propagation effects include scattering, absorption, refraction and ducting), and (3) comparing the directivity patterns and raytracing calculations with type II and type III burst intensity profiles obtained simultaneously by the widely separated Ulysses and Wind spacecraft.
DE: 7534 Radio emissions
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting