Abstract
White-light flares are the flares with emissions visible in the optical continuum. They are thought to be rare and pose the most stringent requirements in energy transport and heating in the lower atmosphere. Here we present a nearly circular white-light flare on 10 March 2015 that was well observed by the Optical and Near-infrared Solar Eruption Tracer and Solar Dynamics Observatory. In this flare, there appear simultaneously both impulsive and gradual white-light kernels. The generally accepted thick-target model would be responsible for the impulsive kernels but not sufficient to interpret the gradual kernels. Some other mechanisms including soft X-ray backwarming or downward-propagating Alfvén waves, acting jointly with electron beam bombardment, provide a possible interpretation. However, the origin of this kind of white-light kernel is still an open question that induces more observations and researches in the future to decipher it.
Highlights
White-light flares are the flares with emissions visible in the optical continuum
The flare was well observed by the Optical and Near-infrared Solar Eruption Tracer (ONSET)[34]
We find a white-light enhancement at Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager (HMI) 6173 Å (Fig. 1i–l)
Summary
White-light flares are the flares with emissions visible in the optical continuum. They are thought to be rare and pose the most stringent requirements in energy transport and heating in the lower atmosphere. We present a nearly circular white-light flare on 10 March 2015 that was well observed by the Optical and Near-infrared Solar Eruption Tracer and Solar Dynamics Observatory In this flare, there appear simultaneously both impulsive and gradual white-light kernels. Solar flares can show an enhanced emission at the visible continuum, besides the enhanced spectral lines that are formed in the chromosphere and above These flares are called white-light flares[3]. When reconnection takes place at the null point or the separatrix layer, flare emissions at the footpoints of the fan field lines would constitute a closed or open circle-like flare ribbon. We report a very rare circular white-light flare that consists of several bright kernels in the white-light continuum, as well as in the Hα line and ultraviolet (UV) channels. The circular flare ribbon, distinct white-light kernels, and peculiar magnetic structure make this flare a unique event among the white-light flares observed so far
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