Analysis of the time profile of type III bursts at meter wavelengths

The time profile of two sets of isolated type III bursts, observed in the meter wavelength range at the Trieste Astronomical Observatory, was analyzed using a Fourier transform technique in order to accurately determine the decay constant of the exponential phase and to derive the exciter time profi...

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Bibliographic Details
Published in:Solar physics 1990-12, Vol.130 (1-2), p.131-138
Main Authors: ABRAMI, A, MESSEROTTI, M, ZLOBEC, P, KARLICKY, M
Format: Article
Language:English
Subjects:
Astronomy
Earth, ocean, space
Exact sciences and technology
Flares, bursts, and related phenomena
Solar physics
Solar system
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Summary:The time profile of two sets of isolated type III bursts, observed in the meter wavelength range at the Trieste Astronomical Observatory, was analyzed using a Fourier transform technique in order to accurately determine the decay constant of the exponential phase and to derive the exciter time profile. The decay constant ( tau ) was found to be correlated with the exciter duration (D sub(e) ), suggesting that the damping of plasma waves is not of collisional origin and confirming results obtained by previous authors at lower frequencies. In particular, two distributions can be identified in the ( tau -D sub(e) ) plane and fitted by two nearly parallel lines, which could be the signature of different decay processes. Moreover, the damping constant observed at higher frequencies (327 and 408 MHz) has the same dependence on exciter duration as that at the lower frequency (237 MHz), also in disagreement with the collisional hypothesis.
ISSN:0038-0938
1573-093X
DOI:10.1007/BF00156784