Features of correlation curves of the Siberian Radioheliograph

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Abstract
Correlation curves of the multi-frequency Siberian Radioheliograph (SRH) provide a sensitive indication and demonstrative representation of monitoring the microwave life of the active Sun. We derive approximate relationships and briefly discuss the contribution of the quiet Sun, active regions, radio bursts, satellites, and atmospheric absorption to the radioheliograph’s correlation response. The estimates are obtained under the assumption that the activity centers and the quiet Sun are homogeneous disks of different sizes and brightness. The sensitivity of the correlation curves to weak sources of small angular sizes is due to their wide spatial spectrum. The wide spectrum means that each pair of antennas produces a noticeable interferometric response, so the total response is significant. The correlation curves allow us to estimate spatial sizes of the radio burst source at different frequencies, but do not allow us to calculate the shape of its radio spectrum. Variability in the atmospheric water content over time creates fluctuations of the received solar radio flux. The correlation response is much less susceptible to this factor.

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