Measurements of solar EUV and soft X ray emission during sudden frequency deviations

Abstract

Broadband sensors aboard the Solrad 11B satellite measured solar emission in the 0.5‐ to 3‐Å, 1‐ to 8‐Å, 8‐ to 20‐Å, 100‐ to 500‐Å, and 700‐ to 1030‐Å bands during six sudden frequency deviation (SFD) events in 1977. Simultaneous analysis of the solar measurements and the SFD sonograms led to a proposed extension of an existing model to provide a qualitative description of the influence of solar flare emission on SFD development throughout the course of an SFD event. The proposed model clearly reflects the observed greater importance of the rate of change, rather than the magnitude, of solar emission during the early phases of an SFD and then a shift of dominance to solar emission magnitude as the SFD progresses. The observations also demonstrate that solar emission at wavelengths less than 20 Å does not cause the positive frequency deviation peaks in larger SFD events.