A self-adaptive method for the determination of solar bursts for high-resolution solar radio spectrometer

Abstract

The solar radio spectrum analyzer is the main means of observing solar radio bursts. Although increasing the temporal resolution allows the fine structure of the solar radio spectrum to be observed in more detail, it also increases exponentially the amount of data received, thereby creating difficulties for the receiving system. To reduce the amount of data handled by the high-time-resolved spectrometer when the Sun is quiet, this paper proposes a self-adaptive method for determining solar bursts by selecting 20 frequencies for radio flux profiles. A solar burst is assumed to be occurring if the radio flux increases by a factor of 200 in 500 ms at one or more frequencies, whereupon the data are stored with a time resolution of up to 1 ms. The end of the burst is determined when the real-time flux drops below the average flux over this 500 ms period. Finally, the data observed every 100 ms during the quiet Sun are averaged and stored, thereby reducing the amount of data storage. The method has been commissioned at the Chashan Solar Observatory in China: during solar flares and coronal mass ejections, the fine structure in the corresponding radio spectra is recorded with high time resolution to understand better the associated dynamic processes, whereas when the Sun is quiet the data are saved at low time resolution, thereby reducing the amount of stored data by a factor of 100 (can be set as needed). All of this helps make the system suitable for long-term observation. As for (i) the time resolutions of the data stored in the solar-burst and quiet periods and (ii) the parameters used to judge the threshold of a radio burst (e.g., 500 ms, 200 times, etc.), these can be set and changed as required. The data-processing method used in this paper can act as a reference for similar high-speed big-data systems.