The origin of quasi-periodicities during circular ribbon flares. (arXiv:2008.02010v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kashapova_L/0/1/0/all/0/1">L. K. Kashapova</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kupriyanova_E/0/1/0/all/0/1">E. G. Kupriyanova</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Xu_Z/0/1/0/all/0/1">Z. Xu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reid_H/0/1/0/all/0/1">H. A. S. Reid</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kolotkov_D/0/1/0/all/0/1">D. Y. Kolotkov</a>
Solar flares with a fan-spine magnetic topology can form circular ribbons.
The previous study based on Halpha line observations of the solar flares
during March 05, 2014 by Xu et al. (2017) revealed uniform and continuous
rotation of the magnetic fan-spine. Preliminary analysis of the flare time
profiles revealed quasi-periodic pulsations (QPPs) with similar properties in
hard X-rays, Halpha, and microwaves. In this work, we address which process
the observed periodicities are related to: periodic acceleration of electrons
or plasma heating? QPPs are analysed in the Halpha emission from the centre of
the fan (inner ribbon R1), a circular ribbon (R2), a remote source (R3), and an
elongated ribbon (R4) located between R2 and R3. The methods of correlation,
Fourier, wavelet, and empirical mode decomposition are used. QPPs in Halpha
emission are compared with those in microwave and X-ray emission. We found
multi-wavelength QPPs with periods around 150 s, 125 s, and 190 s. The 150-s
period is seen to co-exist in Halpha, hard X-rays, and microwave emissions,
that allowed us to connect it with flare kernels R1 and R2. These kernels
spatially coincide with the site of the primary flare energy release. The 125-s
period is found in the Halpha emission of the elongated ribbon R4 and the
microwave emission at 5.7 GHz during the decay phase. The 190-s period is
present in the emission during all flare phases in the Halpha emission of both
the remote source R3 and the elongated ribbon R4, in soft X-rays, and
microwaves at 4–8 GHz. We connected the dominant 150-s QPPs with the slipping
reconnection mechanism occurring in the fan. We suggested that the period of
125 s in the elongated ribbon can be caused by a kink oscillation of the outer
spine connecting the primary reconnection site with the remote footpoint. The
period of 190 s is associated with the 3-min sunspot oscillations.
Solar flares with a fan-spine magnetic topology can form circular ribbons.
The previous study based on Halpha line observations of the solar flares
during March 05, 2014 by Xu et al. (2017) revealed uniform and continuous
rotation of the magnetic fan-spine. Preliminary analysis of the flare time
profiles revealed quasi-periodic pulsations (QPPs) with similar properties in
hard X-rays, Halpha, and microwaves. In this work, we address which process
the observed periodicities are related to: periodic acceleration of electrons
or plasma heating? QPPs are analysed in the Halpha emission from the centre of
the fan (inner ribbon R1), a circular ribbon (R2), a remote source (R3), and an
elongated ribbon (R4) located between R2 and R3. The methods of correlation,
Fourier, wavelet, and empirical mode decomposition are used. QPPs in Halpha
emission are compared with those in microwave and X-ray emission. We found
multi-wavelength QPPs with periods around 150 s, 125 s, and 190 s. The 150-s
period is seen to co-exist in Halpha, hard X-rays, and microwave emissions,
that allowed us to connect it with flare kernels R1 and R2. These kernels
spatially coincide with the site of the primary flare energy release. The 125-s
period is found in the Halpha emission of the elongated ribbon R4 and the
microwave emission at 5.7 GHz during the decay phase. The 190-s period is
present in the emission during all flare phases in the Halpha emission of both
the remote source R3 and the elongated ribbon R4, in soft X-rays, and
microwaves at 4–8 GHz. We connected the dominant 150-s QPPs with the slipping
reconnection mechanism occurring in the fan. We suggested that the period of
125 s in the elongated ribbon can be caused by a kink oscillation of the outer
spine connecting the primary reconnection site with the remote footpoint. The
period of 190 s is associated with the 3-min sunspot oscillations.
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