Coherent microwave emission as an indicator of non-thermal energy release at a coronal X-ray point

A response has been found in a narrow band 5–7 GHz of microwave emission to the appearance of a coronal X-ray point. The emission source is a short X-ray loop located in the tail part of an active region and occurring when magnetic fields are reconnected near the footpoints of high and low loops rooted in nearby magnetic pores of the opposite polarity. The power of energy release is low and no response of the hot plasma component was observed in hard X-rays. Analysis of images in soft X-ray and extreme UV radiation shows that microwave emission has a coherent nature and is generated at a frequency of about twice the plasma frequency by electrons with energies above several tens of keV. The result indicates a high diagnostic potential of microwave observations to detect acceleration processes in weak transitory events and can be useful for observation planning with new generation radioheliographs currently under development.