Signs of Preflare Situation in Solar Ultraviolet and Microwave Emission

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Abstract
The spatial dynamics of microwave emission (data from the Nobeyama Radioheliograph) of active regions with a complex magnetic field configuration before powerful flares, as well as the fine structure of active sources of ultraviolet (UV) emission based on AIA/SDO data, are studied. It is shown that there is unsteady behavior of microwave sources, along with the ignition of a system of crossed UV loops (X-structures). A class-M X-ray flare occurs after several hours at the site of ignition of the intersecting UV loops. The similar behavior observed in microwave and ultraviolet emission in the five active regions studied by us likely serves as a sign of a preflare situation in the active region on the Sun.
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