Abstract
Hard X-ray bursts have been observed from two 1B flares located in the same sunspot region and separated in time by about 70 min on 8 December 1970. The bursts are composed by many ‘flashes’ of 2 to 20 seconds duration. Power spectrum analysis reveals no strong periodicities although a significant peak appears at 7.5 s. The characteristic times of 2 to 20 s do not seem likely to be electron transit times since the flare size is so small. These times are evidently connected with the acceleration of the electrons. Fitting Takakura's model of the radio noise region to the observations we find this region to be small but the density of electrons above 100 keV is high, on the order of 107 cm-3.
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Anderson, K.A., Mahoney, W.A. Hard solar flare X-ray Bursts on 8 December 1970. Sol Phys 35, 419–430 (1974). https://doi.org/10.1007/BF00151965
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DOI: https://doi.org/10.1007/BF00151965