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The observation of 10–50 KeV solar flare X-rays by the OGO satellites and their correlation with solar radio and energetic particle emission

Published online by Cambridge University Press:  14 August 2015

R. L. Arnoldy ,
S. R. Kane  and
J. R. Winckler
R. L. Arnoldy
Affiliation:
School of Physics and Astronomy, University of Minnesota, Minneapolis, Minn., U.S.A.
S. R. Kane
Affiliation:
School of Physics and Astronomy, University of Minnesota, Minneapolis, Minn., U.S.A.
J. R. Winckler
Affiliation:
School of Physics and Astronomy, University of Minnesota, Minneapolis, Minn., U.S.A.

Abstract

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More than 70 cases have been observed of energetic solar flare X-ray bursts by large ionization chambers on the OGO satellites in space. The ionization chambers have an energy range between 10 and 50 KeV for X-rays and are also sensitive to solar protons and electrons. A study has been made of the X-ray microwave relationship, and it is found that the total energy released in the form of X-rays between 10 and 50 KeV is approximately proportional to the peak or total energy simultaneously released in the form of microwave emission. For a given burst the rise time, decay time and total duration are similar for the 10–50 KeV X-rays and the 3 to 10 cm radio emission. Roughly exponential decay phases are observed for both emissions with time constants between 1 and 10 min. All 3 or 10 cm radio bursts with peak intensity greater than 80 solar flux units are accompanied by an X-ray burst greater than 3 × 10−7 ergs cm−2 sec−1 peak intensity. The probability of detecting such X-ray events is low unless the radio spectrum extends into the centimetric range of wavelengths. The best correlation between cm-λ and energetic X-rays is observed for the first event in a flare. Subsequent structure and second bursts may not correspond even when the radio emission is rich in the microwave component. The mechanism for the energetic X-rays is shown to be bremsstrahlung probably of fast electrons on a cooler plasma. If the radio emission is assumed to be synchrotron radiation then a relationship is developed between density and magnetic field which meets the observed quantitative results. One finds, on the average, that 5 × 10−54 joules m−2 (CPS)−1 of microwave energy at the Earth are required per electron at the Sun to provide the radio emission for the various events.

A strong correlation between interplanetary solar flare electrons observed by satellite and X-ray bursts is shown to exist. This correlation is weak for solar proton events. One may infer a strong propagation asymmetry for solar flare electrons along the spiral interplanetary magnetic field.

Type
Part VI: Transient Phenomena
Information
Symposium - International Astronomical Union , Volume 35: Structure and Development of Solar Active Regions , 1968 , pp. 490 - 509
Copyright
Copyright © Reidel 1968 

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