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Ground Level Enhancements (GLEs) of cosmic-ray intensity occur, on average,once a year. Due to their rareness, studying the solar sources of GLEs isespecially important to approach understanding their origin. The SOL2001-12-26eruptive-flare event responsible for GLE63 seems to be challenging in someaspects. Deficient observations limited its understanding. Analysis of extraobservations found for this event provided new results shading light on theflare. This article addresses the observations of this flare with the SiberianSolar Radio Telescope (SSRT). Taking advantage of its instrumentalcharacteristics, we analyze the detailed SSRT observations of a majorlong-duration flare at 5.7 GHz without cleaning the images. The analysisconfirms that the source of GLE63 was associated with an event in active region9742 that comprised two flares. The first flare (04:30-05:03 UT) reached a GOESimportance of about M1.6. Two microwave sources were observed, whose brightnesstemperatures at 5.7 GHz exceeded 10 MK. The main flare, up to the M7.1importance, started at 05:04 UT, and occurred in strong magnetic fields. Theobserved microwave sources reached about 250 MK. They were not static. Havingappeared on the weaker-field periphery of the active region, the microwavesources moved toward each other nearly along the magnetic neutral line,approaching a stronger-field core of the active region, and then moved awayfrom the neutral line like expanding ribbons. These motions rule out anassociation of the non-thermal microwave sources with a single flaring loop.

The 26 December 2001 Solar Event Responsible for GLE63. I. Observations of a Major Long-Duration Flare with the Siberian Solar Radio Telescope