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Polarization and Position Measurements of Type III Bursts

Published online by Cambridge University Press:  14 August 2015

S. Suzuki ,
G.A. Dulk  and
K. V. Sheridan
S. Suzuki
Affiliation:
Division of Radiophysics, CSIRO, Sydney, Australia
G.A. Dulk
Affiliation:
Division of Radiophysics, CSIRO, Sydney, Australia
K. V. Sheridan
Affiliation:
Division of Radiophysics, CSIRO, Sydney, Australia

Abstract

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We report on the positional and polarization characteristics of Type III bursts in the range 24–220 MHz as measured by the Culgoora radioheliograph, spectrograph and spectropolarimeter. Our study includes 997 bursts which are of two classes: fundamental-harmonic (F-H) pairs and “structureless” bursts with no visible F-H structure. In a paper published elsewhere (Dulk and Suzuki, 1979) we give a detailed description and include observations of source sizes, heights and brightness temperatures. Here we concentrate on the polarization of the bursts and the variation of polarization from centre to limb. The observed centre-to-limb decrease in polarization approximately follows a cosine law. This decrease is not as predicted by simple theory but is consistent with other observations which imply that open field lines from an active region diverge strongly. The observed o-mode polarization of harmonic radiation implies that the wave vectors of Langmuir waves are always parallel, within about 20°, to the magnetic field, while the constancy of H polarization with frequency implies that the ratio fB/fP, the Alfvén speed vA and the plasma beta are constant with height on the open field lines above an active region. Finally, we infer that some factor, in addition to the magnetic field strength, controls the polarization of F radiation.

Type
Session V - Solar Bursts - Meter-Decameter Wavelengths
Information
Symposium - International Astronomical Union , Volume 86: Radio Physics of the Sun , 1980 , pp. 315 - 322
Copyright
Copyright © Reidel 1980 

References

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