Fine Structure of the Solar Corona in High-Frequency Resolution Radio Observations

Lebedev M. K.; Bogod V. M.; Ovchinnikova N. E.

The existence of continuous cooling and heating processes is an important condition governing the behavior of the solar corona, which is characterized by temperatures of several million Kelvin. These processes can be significantly influenced by small-scale coronal formations, which largely determine the thermal balance of the corona and solar-wind disturbances. High-sensitivity observations of polarized radiation allow us to evaluate the complex structure of magnetic fields that accumulate the energy necessary to excite coronal eruptions, bursts and flares. However, at high altitudes the corona becomes optically thin, and observations of it pose a major challenge, requiring the use of instruments with a large effective area. Many researchers note that the emerging field of coronal magnetometry is hard to develop due to the fact that experimental observations in optical range are limited by the low plasma density in the corona, high temperature, and insufficient sensitivity of the instruments. In contrast, higher sensitivity is achievable in the radio frequency range. In particular, the 1–3 GHz range is optimal for detecting very weak coronal structures of emerging activity, despite limitations in spatial resolution. To carry out radio requency observations of the corona on the RATAN-600 large reflector-type radio telescope, a wide-range spectrometer in the range of 1–3 GHz was created. It has continuous coverage of the entire frequency range with maximum frequency and time resolutions, as well as high sensitivity to radiation flux. The results of the first series of observations of weak coronal structures are presented, and their interpretation in terms of their effect on thermal processes in the corona is discussed.