Fast Mid-IR Flashes Detected During Small Solar X-Ray Bursts

Solar observations in the mid-infrared 8 – 14 μm band continuum were carried out with cadence of 5 frames per second, in December 2007. Rapid small heated sources, with a typical duration of the order of seconds, were found on the bright plage-like areas around sunspots, in association with relatively weak GOES soft X-ray bursts. This work presents the analysis of fast mid-infrared flashes detected during a GOES B2.0-class event on 10 December 2007, beginning at about 10:40 UT. Rapid brightness temperature enhancements of 0.5 to 2.0 K were detected at the Earth by a microbolometer array, using a telescope with 10.5 cm diameter aperture producing a diffraction-limited photometric beam of 25 arc sec. The minimum detectable temperature change was of 0.1 K. The corresponding fluxes are 30 – 130 solar flux units. At the solar surface the estimated rapid brightenings represented a temperature enhancement of 50 – 150 K.