A MULTI-INSTRUMENT ANALYSIS OF a C4.1 FLARE OCCURRING IN a Δ SUNSPOT

Guglielmino, S. L.; Zuccarello, F.; Romano, P.; Cristaldi, Antonio; Ermolli, I.; Criscuoli, S.; Falco, M.

doi:10.3847/0004-637x/819/2/157

Cited by 10 publications

(10 citation statements)

References 72 publications

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“…The slipping/slip-running reconnection in a fan-spine magnetic topology seems to be also associated with the occurrence homologous jets, as observed by Wang & Liu (2012), and the multiple-ribbon formation (e.g., Guglielmino et al 2016).…”

Section: Introductionmentioning

confidence: 87%

Observation of a 3D Magnetic Null Point

Romano¹,

Falco²,

Guglielmino³

et al. 2017

ApJ

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We describe high resolution observations of a GOES B-class flare characterized by a circular ribbon at chromospheric level, corresponding to the network at photospheric level. We interpret the flare as a consequence of a magnetic reconnection event occurred at a three-dimensional (3D) coronal null point located above the supergranular cell. The potential field extrapolation of the photospheric magnetic field indicates that the circular chromospheric ribbon is cospatial with the fan footpoints, while the ribbons of the inner and outer spines look like compact kernels. We found new interesting observational aspects that need to be explained by models: 1) a loop corresponding to the outer spine became brighter a few minutes before the onset of the flare; 2) the circular ribbon was formed by several adjacent compact kernels characterized by a size of 1 ′′ -2 ′′ ; 3) the kernels with stronger intensity emission were located at the outer footpoint of the darker filaments departing radially from the center of the supergranular cell; 4) these kernels start to brighten sequentially in clockwise direction; 5) the site of the 3D null point and the shape of the outer spine were detected by RHESSI in the low energy channel between 6.0 and 12.0 keV. Taking into account all these features and the length scales of the magnetic systems involved by the event we argued that the low intensity of the flare may be ascribed to the low amount of magnetic flux and to its symmetric configuration.

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Section: Introductionmentioning

confidence: 87%

Observation of a 3D Magnetic Null Point

Romano¹,

Falco²,

Guglielmino³

et al. 2017

ApJ

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“…For slow evolving processes, whose characteristic time is much longer than the scanning time, this is a reasonable assumption. For highly dynamic phenomena, such as flares (Guglielmino et al 2016;Kleint 2017) or umbral flashes (UFs, de la Cruz Rodríguez et al 2013;Henriques et al 2017), it can potentially lead to a misinterpretation of the polarimetric profiles.…”

Section: Introductionmentioning

confidence: 99%

Inversions of synthetic umbral flashes: Effects of scanning time on the inferred atmospheres

Felipe

Socas‐Navarro

Przybylski

2018

A&A

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Context. The use of instruments that record narrow band images at selected wavelengths is a common approach in solar observations. They allow the scanning of a spectral line by sampling the Stokes profiles with two-dimensional images at each line position, but require a compromise between spectral resolution and temporal cadence. The interpretation and inversion of spectropolarimetric data generally neglect the changes in the solar atmosphere during the scanning of the line profiles. Aims. We evaluate the impact of the time-dependent acquisition of different wavelengths on the inversion of spectropolarimetric profiles from chromospheric lines during umbral flashes. Methods. Numerical simulations of non-linear wave propagation in a sunspot model were performed with the code MANCHA. Synthetic Stokes parameters in the Ca ii 8542 Å line in NLTE were computed for an umbral flash event using the code NICOLE. Artificial profiles with the same wavelength coverage and temporal cadence from reported observations were constructed and inverted. The inferred atmospheric stratifications were compared with the original simulated models. Results. The inferred atmospheres provide a reasonable characterization of the thermodynamic properties of the atmosphere during most of the phases of the umbral flash. Only at the early stages of the flash, when the shock wave reaches the formation height of the Ca ii 8542 Å line, the Stokes profiles present apparent wavelength shifts and other spurious deformations. These features are misinterpreted by the inversion code, which can return unrealistic atmospheric models from a good fit of the Stokes profiles. The misguided results include flashed atmospheres with strong downflows, even though the simulation exhibits upflows during the umbral flash, and large variations in the magnetic field strength. Conclusions. Our analyses validate the inversion of Stokes profiles acquired by sequentially scanning certain selected wavelengths of a line profile, even in the case of rapidly-changing chromospheric events such as umbral flashes. However, the inversion results are unreliable during a short period at the development phase of the flash.

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“…This AR did not follow the helicity hemispheric rule. Another analysis of the helicity for this AR can be found in Guglielmino et al (2016).…”

Section: Flare-quiet Arsmentioning

confidence: 99%

Comparative case study of two methods to assess the eruptive potential of selected active regions

Zuccarello,

Ermolli,

Korsos

et al. 2021

Preprint

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Solar eruptive events, like flares and coronal mass ejections, are characterized by the rapid release of energy that can give rise to emission of radiation across the entire electromagnetic spectrum and to an abrupt significant increase in the kinetic energy of particles.These energetic phenomena can have important effects on the Space Weather conditions and therefore it is necessary to understand their origin, in particular, what is the eruptive potential of an active region (AR). In these case studies, we compare two distinct methods that were used in previous works to investigate the variations of some characteristic physical parameters during the pre-flare states of flaring ARs. These methods consider: i) the magnetic flux evolution and the magnetic helicity accumulation, and ii) the fractal and multi-fractal properties of flux concentrations in ARs. Our comparative analysis is based on time series of photospheric data obtained by the Solar Dynamics Observatory between March 2011 and June 2013. We selected two distinct samples of ARs: one is distinguished by the occurrence of more energetic M-and X-class flare events, that may have a rapid effect on not just the near-Earth space, but also on the terrestrial environment; the second is characterized by no-flares or having just few C-and B-class flares. We found that the two tested methods complement each other in their ability to assess the eruptive potentials of ARs and could be employed to identify ARs

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A MULTI-INSTRUMENT ANALYSIS OF a C4.1 FLARE OCCURRING IN a Δ SUNSPOT

Cited by 10 publications

References 72 publications

Observation of a 3D Magnetic Null Point

Observation of a 3D Magnetic Null Point

Inversions of synthetic umbral flashes: Effects of scanning time on the inferred atmospheres

Comparative case study of two methods to assess the eruptive potential of selected active regions

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