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Oscillations and Waves in Radio Source of Drifting Pulsation Structures

Abstract

Drifting pulsation structures (DPSs) are considered to be radio signatures of the plasmoids formed during magnetic reconnection in the impulsive phase of solar flares. In the present paper we analyze oscillations and waves in seven examples of drifting pulsation structures, observed by the 800 – 2000 MHz Ondřejov Radiospectrograph. For their analysis we use a new type of oscillation maps, which give us much more information as regards processes in DPSs than that in previous analyses. Based on these oscillation maps, made from radio spectra by the wavelet technique, we recognized quasi-periodic oscillations with periods ranging from about 1 to 108 s in all studied DPSs. This strongly supports the idea that DPSs are generated during a fragmented magnetic reconnection. Phases of most the oscillations in DPSs, especially for the period around 1 s, are synchronized (“infinite” frequency drift) in the whole frequency range of DPSs. For longer periods in some DPSs we found that the phases of the oscillations drift with the frequency drift in the interval from −17 to \(+287~\mbox{MHz}\,\mbox{s}^{-1}\). We propose that these drifting phases can be caused (a) by the fast or slow magnetosonic waves generated during the magnetic reconnection and propagating through the plasmoid, (b) by a quasi-periodic structure in the plasma inflowing to the reconnection forming a plasmoid, and (c) by a quasi-periodically varying reconnection rate in the X-point of the reconnection close to the plasmoid.

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Acknowledgements

This research was supported by Grants 16-13277S and 17-16447S of the Grant Agency of the Czech Republic. This work was supported by the Science Grant Agency project VEGA 2/0004/16 (Slovakia). Help of the Bilateral Mobility Projects SAV-16-03 and SAV-18-01 of the SAS and CAS is acknowledged. This article was created in the project ITMS No. 26220120029, based on the supporting operational Research and development program financed from the European Regional Development Fund. This research has made use of NASA’s Astrophysics Data System. The wavelet analysis was performed with software based on tools provided by C. Torrence and G.P. Compo at http://paos.colorado.edu/research/wavelets .

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Correspondence to Ján Rybák.

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Karlický, M., Rybák, J. & Bárta, M. Oscillations and Waves in Radio Source of Drifting Pulsation Structures. Sol Phys 293, 62 (2018). https://doi.org/10.1007/s11207-018-1282-9

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Keywords

  • Sun: flares
  • Sun: radio radiation
  • Sun: oscillations