Spectral structures and their generation mechanisms for solar radio type-I burstS

K. Iwai, Y. Miyoshi, S. Masuda, F. Tsuchiya, A. Morioka, H. Misawa

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

The fine spectral structures of solar radio type-I bursts were observed by the solar radio telescope AMATERAS. The spectral characteristics, such as the peak flux, duration, and bandwidth, of the individual burst elements were satisfactorily detected by the highly resolved spectral data of AMATERAS with the burst detection algorithm that is improved in this study. The peak flux of the type-I bursts followed a power-law distribution with a spectral index of 2.9-3.3, whereas their duration and bandwidth were distributed more exponentially. There were almost no correlations between the peak flux, duration, and bandwidth. That means there was no similarity in the shapes of the burst spectral structures. We defined the growth rate of a burst as the ratio between its peak flux and duration. There was a strong correlation between the growth rate and peak flux. These results suggest that the free energy of type-I bursts that is originally generated by nonthermal electrons is modulated in the subsequent stages of the generation of nonthermal electrons, such as plasma wave generation, radio wave emissions, and propagation. The variation of the timescale of the growth rate is significantly larger than that of the coronal environments. These results can be explained by the situation wherein the source region may have the inhomogeneity of an ambient plasma environment, such as the boundary of open and closed field lines, and the superposition of entire emitted bursts was observed by the spectrometer.

Original languageEnglish
Article number4
JournalAstrophysical Journal
Volume789
Issue number1
DOIs
Publication statusPublished - 2014 Jul 1

Keywords

  • Sun: corona
  • Sun: radio radiation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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