Sources of Quasi-periodic Pulses in the Flare of 18 August 2012

• Published in: Solar physics 2016-02, Vol.291 (2), p.445-463
• Main Authors: Altyntsev, A., Meshalkina, N., Mészárosová, H., Karlický, M., Palshin, V., Lesovoi, S.
• Format: Article
• Language: English
• Subjects: Analysis; Astrophysics and Astroparticles; Atmospheric Sciences; Broadband; Channels; Emittance; Flares; Limbs; Microwaves; Physics; Physics and Astronomy; Radio telescopes; Solar energy; Solar flares; Solar physics; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Spectra; X-rays
• ISSN: 0038-0938; 1573-093X
• DOI: 10.1007/s11207-016-0846-9

We analyzed spatial and spectral characteristics of quasi-periodic pulses (QPP) for the limb flare on 18 August 2012, using new data from a complex of spectral and imaging instruments developed by the Siberian Solar Radio Telescope team and the Wind/Konus γ -ray spectrometer. A sequence of broadband pulses with periods of approximately ten seconds were observed in X-rays at energies between 25 keV and 300 keV, and in microwaves at frequencies from a few GHz up to 34 GHz during an interval of one minute. The QPP X-ray source was located slightly above the limb where the southern legs of large and small EUV loop systems were close to each other. Before the QPPs occurred, the soft X-ray emission and the Ramaty High Energy Solar Spectroscopic Imager signal from the energy channels below 25 keV were gradually arising for several minutes at the same location. It was found that each X-ray pulse showed a soft-hard-soft behavior. The 17 and 34 GHz microwave sources were at the footpoints of the small loop system, the source emitting in the 4.2 – 7.4 GHz band in the large system. The QPPs were probably generated by modulated acceleration processes in the energy-release site. We determined the plasma parameters in the radio sources by analyzing the spectra. The microwave pulses might be explained by relatively weak variations of the spectral hardness of the emitting electrons.