Abstract
We discuss a solar flare microwave burst complex, which included a major structure consisting of some 13 spikes of 60 ms FWHM each, observed 21 May, 1984 at 90 GHz (3 mm). It was associated with a simultaneous very hard X-ray burst complex. We suggest that the individual spikes of both bursts were caused by the same electron population: the X-bursts by their bremsstrahlung, and the microwave bursts by their gyrosynchrotron emission. This latter conclusion is based on the evidence that the radio turnover frequency was ≤ 150 GHz. It follows that the emission sources were characterized by an electron density of about 1011 cm−3, a temperature of 5 × 108 K and a magnetic field of about 1400–2000 G. They had a size of about 350 km; if the energy release is caused by reconnection the sources of primary instability could have been smaller and in the form of thin sheets with reconnection speed at a fraction of the Alfvén velocity and burst-like energy injections of ≈ 1027 erg during about 50 ms each. The energized plasma knots lost their injection energy by saturated convective flux (collisionless conduction) in about 30 ms.
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De Jager, C., Kuijpers, J., Correia, E. et al. A high-energy solar flare burst complex and the physical properties of its source region. Sol Phys 110, 317–326 (1987). https://doi.org/10.1007/BF00206427
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DOI: https://doi.org/10.1007/BF00206427