Microwave features of behind-the-limb (BLT) solar flares with significant emission in hard X-ray

Larisa Kashapova, Institute of Solar-Terrestrial Physics SB RAS

Solar flares occurring behind the limb (BTL) often show high coronal sources, while the foot points are hidden from direct view. Usually, this coronal emission has a thermal origin. But in some cases, the coronal sources demonstrate the clear presence of non-thermal contribution. Such events occur rarely and are still only weakly understood. Such X-ray emission could be generated both by electrons in the acceleration site, and trapped electrons. Combination of the X-ray and radio observations and especially microwave data help to clarify the origin of emitting electrons. We present results of the microwave data analysis for about 20 events selected from continuous observations of the Konus-WIND instrument in the hard X-ray range from November 1994 till the present. The preliminary criterion for BTL candidate selection was a low thermal soft X-ray response as compared to prominent non-thermal hard X-ray emission. Konus-WIND does not provide any spatial information, and we excluded all on-disc and limb flares from the preliminary list based on localization obtained from different instruments providing images at a different wavelength. We discuss the correlation between time profiles and spectral properties of microwave and X-ray observations for this BTL event sample. L.K. Kashapova thanks the Russian Science Foundation grant 18-12-00172 for financial support.