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Theory of Type 3 and Type 2 Solar Radio EmissionsThe main features of some current theories of type III and type II bursts are outlined. Among the most common solar radio bursts, type III bursts are produced at frequencies of 10 kHz to a few GHz when electron beams are ejected from solar active regions, entering the corona and solar wind at typical speeds of 0.1c. These beams provide energy to generate Langmuir waves via a streaming instability. In the current stochastic-growth theory, Langmuir waves grow in clumps associated with random low-frequency density fluctuations, leading to the observed spiky waves. Nonlinear wave-wave interactions then lead to secondary emission of observable radio waves near the fundamental and harmonic of the plasma frequency. Subsequent scattering processes modify the dynamic radio spectra, while back-reaction of Langmuir waves on the beam causes it to fluctuate about a state of marginal stability. Theories based on these ideas can account for the observed properties of type III bursts, including the in situ waves and the dynamic spectra of the radiation. Type 11 bursts are associated with shock waves propagating through the corona and interplanetary space and radiating from roughly 30 kHz to 1 GHz. Their basic emission mechanisms are believed to be similar to those of type III events and radiation from Earth's foreshock. However, several sub-classes of type II bursts may exist with different source regions and detailed characteristics. Theoretical models for type II bursts are briefly reviewed, focusing on a model with emission from a foreshock region upstream of the shock for which observational evidence has just been reported.
Document ID
20000094839
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Robinson, P. A.
(Sydney Univ. Australia)
Cairns, I. H.
(Sydney Univ. Australia)
Date Acquired
August 19, 2013
Publication Date
January 1, 2000
Publication Information
Publication: Radio Astronomy at Long Wavelengths
Publisher: American Geophysical Union
Subject Category
Solar Physics
Report/Patent Number
Geophysical-Monograph-119
Funding Number(s)
CONTRACT_GRANT: NAG5-6127
CONTRACT_GRANT: NAG5-6369
Distribution Limits
Public
Copyright
Other

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