Do All Flares Have White-Light Emission?

Jess, D. B.; Mathioudakis, M.; Crockett, P. J.; Keenan, F. P.

doi:10.1086/595588

Cited by 92 publications

(110 citation statements)

References 31 publications

(36 reference statements)

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“…Gamma rays typically accompany HXR when detectable (e.g., Cliver et al 1994;Shih et al 2009) Matthews et al 2003;Hudson et al 2006;Wang 2009) make it possible to detect much weaker and therefore more numerous events. Hudson et al (2006) report a GOES C1.3 event observed by TRACE, and Jess et al (2008) found a GOES C2.0 event even with ground-based observations.…”

Section: Flare Morphologymentioning

confidence: 89%

Global Properties of Solar Flares

2011

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This article broadly reviews our knowledge of solar flares. There is a particular focus on their global properties, as opposed to the microphysics such as that needed for magnetic reconnection or particle acceleration as such. Indeed solar flares will always remain in the domain of remote sensing, so we cannot observe the microscales directly and must understand the basic physics entirely via the global properties plus theoretical inference. The global observables include the general energetics-radiation in flares and mass loss in coronal mass ejections (CMEs)-and the formation of different kinds of ejection and global wave disturbance: the type II radio-burst exciter, the Moreton wave, the EIT "wave", and the "sunquake" acoustic waves in the solar interior. Flare radiation and CME kinetic energy can have comparable magnitudes, of order 10 32 erg each for an X-class event, with the bulk of the radiant energy in the visible-UV continuum. We argue that the impulsive phase of the flare dominates the energetics of all of these manifestations, and also point out that energy and momentum in this phase largely reside in the electromagnetic field, not in the observable plasma.

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Section: Flare Morphologymentioning

confidence: 89%

Global Properties of Solar Flares

2011

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“…As our study does not include microflares (i.e., GOES C class and smaller), we cannot state anything regarding this group of events. Nevertheless, WL emission has been reported from C-class flares (Jess et al 2008) and there are GOES A-and B-class flares with relatively intense HXR emissions (of the order of 0.1 photon s Ishikawa et al 2011) for which WL emission could potentially be detectable.…”

Section: Discussionmentioning

confidence: 99%

Correlation of Hard X-Ray and White Light Emission in Solar Flares

Kuhar

Krucker

Oliveros

et al. 2015

ApJ

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A statistical study of the correlation between hard X-ray and white light emission in solar flares is performed in order to search for a link between flare-accelerated electrons and white light formation. We analyze 43 flares spanning GOES classes M and X using observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager and Helioseismic and Magnetic Imager. We calculate X-ray fluxes at 30 keV and white light fluxes at 6173 Å summed over the hard X-ray flare ribbons with an integration time of 45 s around the peak hard-X ray time. We find a good correlation between hard X-ray fluxes and excess white light fluxes, with a highest correlation coefficient of 0.68 for photons with energy of 30 keV. Assuming the thick target model, a similar correlation is found between the deposited power by flare-accelerated electrons and the white light fluxes. The correlation coefficient is found to be largest for energy deposition by electrons above ∼50 keV. At higher electron energies the correlation decreases gradually while a rapid decrease is seen if the energy provided by low-energy electrons is added. This suggests that flare-accelerated electrons of energy ∼50 keV are the main source for white light production.

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“…However, because the TRACE WL/ultraviolet (UV) emission always has a higher contrast than that of the traditional WLFs and the observations are sometimes saturated, it is unclear whether the TRACE continuum is affected by UV emission. Jess et al (2008) used high resolution observations of the one-meter Swedish Solar Telescope to detect WL emission in the blue continuum around 3954 Å with a peak intensity 300% above the quiescent flux in a C2.0 flare. This high emission contrast, although restricted to a small area, is surprising and it remains to be verified whether it is a common feature in WLF observations.…”

Section: Introductionmentioning

confidence: 99%

Understanding the white-light flare on 2012 March 9: evidence of a two-step magnetic reconnection

Hao¹,

Guo²,

Dai³

et al. 2012

A&A

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Aims. We attempt to understand the white-light flare (WLF) that was observed on 2012 March 9 with a newly constructed multiwavelength solar telescope called the Optical and Near-infrared Solar Eruption Tracer (ONSET). Methods. We analyzed WLF observations in radio, Hα, white-light, ultraviolet, and X-ray bands. We also studied the magnetic configuration of the flare via the nonlinear force-free field (NLFFF) extrapolation and the vector magnetic field observed by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). Results. Continuum emission enhancement clearly appeared at the 3600 Å and 4250 Å bands, with peak contrasts of 25% and 12%, respectively. The continuum emission enhancement closely coincided with the impulsive increase in the hard X-ray emission and a microwave type III burst at 03:40 UT. We find that the WLF appeared at one end of either the sheared or twisted field lines or both. There was also a long-lasting phase in the Hα and soft X-ray bands after the white-light emission peak. In particular, a second, yet stronger, peak appeared at 03:56 UT in the microwave band. Conclusions. This event shows clear evidence that the white-light emission was caused by energetic particles bombarding the lower solar atmosphere. A two-step magnetic reconnection scenario is proposed to explain the entire process of flare evolution, i.e., the firststep magnetic reconnection between the field lines that are highly sheared or twisted or both, and the second-step one in the current sheet, which is stretched by the erupting flux rope. The WLF is supposed to be triggered in the first-step magnetic reconnection at a relatively low altitude.

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Do All Flares Have White-Light Emission?

Cited by 92 publications

References 31 publications

Global Properties of Solar Flares

Global Properties of Solar Flares

Correlation of Hard X-Ray and White Light Emission in Solar Flares

Understanding the white-light flare on 2012 March 9: evidence of a two-step magnetic reconnection

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