Statistical study of the correlation of hard X-ray and type III radio bursts in solar flares

Russell J Hamilton, Vahé Petrosian, A. O. Benz

Research output: Contribution to journalArticle

14 Scopus citations


We have analyzed a large number of hard X-ray events which were recorded by the Hard X-Ray Burst Spectrometer (HXRBS) on the Solar Maximum Mission (SMM) during the maximum of solar cycle 21 (ca. 1980) in order to study their statistical correlation with type III bursts. We find that the intensity distribution of the occurrence of hard X-ray bursts which are associated with a type III radio burst is significantly different than the distribution of all hard X-ray bursts which is inconsistent with the statistical independence of the X-ray and type III intensities. The observed distribution of hard X-ray and type III events and their correlations are shown to be satisfactorily described by a bivariate distribution consistent with the assumption of statistical linear dependence of X-ray and radio burst intensities. It is shown that this dependence is consistent with the nonthennal thick-target model for hard X-rays along with optically thick second harmonic emission for type III radiation. From the study of the distribution of hard X-ray and type III burst intensities, we determine that the typical ratio of X-ray intensity (in counts s-1) to type III intensity (in SFU) is ∼10 and that the ratio of the number of X-ray- to type III-producing electrons is ∼103, but that there is a large dispersion in these ratios. The correlation of hard X-ray and type III emission is found to increase slightly with decreasing X-ray spectral index. We discuss how the spectral index dependence of the ratio of X-ray- to type III-producing electrons is related to the observed dependence and show how this can be used to test theoretical models of the impulsive phase. We show that the observed spectral index dependence can be explained by the model published by Petrosian and Leach in 1983 if the accelerated electrons are beamed toward the Sun.

Original languageEnglish (US)
Pages (from-to)644-653
Number of pages10
JournalAstrophysical Journal
Issue number2
Publication statusPublished - Aug 1 1990
Externally publishedYes



  • Sun: flares
  • Sun: radio radiation
  • Sun: X-rays

ASJC Scopus subject areas

  • Space and Planetary Science

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