Magnetic Structure Producing X- And M-Class Solar Flares in Solar Active Region 11158

Inoue, Satoshi; Hayashi, Keiji; Shiota, Daikou; Magara, Tetsuya; Choe, G. S.

doi:10.1088/0004-637x/770/1/79

Cited by 46 publications

(65 citation statements)

References 51 publications

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“…In this method, Equation (1) defines a pseudo-density (ρ), which is proportional to | B |, in order to ease the relaxation by maintaining the Alfvén speed in space (Inoue et al 2013). Equation (2) is the equation of motion for the zero plasma beta condition neglecting gravity.…”

Section: Nlfff Methodsmentioning

confidence: 99%

Magnetohydrodynamic Simulations for Studying Solar Flare Trigger Mechanism

Muhamad¹,

Kusano²,

Inoue³

et al. 2017

ApJ

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In order to understand the flare trigger mechanism, we conducted threedimensional magnetohydrodynamic simulations using a coronal magnetic field model derived from data observed by the Hinode satellite. Several types of magnetic bipoles were imposed into the photospheric boundary of the Non-linear Force-Free Field (NLFFF) model of Active Region NOAA 10930 on 2006 December 13 to investigate what kind of magnetic disturbance may trigger the flare. As a result, we confirm that certain small bipole fields, which emerge into the highly sheared global magnetic field of an active region, can effectively trigger a flare. These bipole fields can be classified into two groups based on their orientation relative to the polarity inversion line: the so called opposite polarity (OP) and reversed shear (RS) structures as it was suggested by Kusano et al. (2012). We also investigated the structure of the footpoints of reconnected field lines. By comparing the distribution of reconstructed field lines and the observed flare ribbons, the trigger structure of the flare can be inferred. Our simulation suggests that the data-constrained simulation taking into account both the large-scale magnetic structure and the small-scale magnetic disturbance such as emerging fluxes is a good way to find out a flare productive active region for space weather prediction.

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Section: Nlfff Methodsmentioning

confidence: 99%

Magnetohydrodynamic Simulations for Studying Solar Flare Trigger Mechanism

Muhamad¹,

Kusano²,

Inoue³

et al. 2017

ApJ

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“…It also produced several Mclass flares during February 13-16 (Inoue et al 2013), after being assigned its number on February 13. Also in this case, E f shows a clear increase with E f − E † f ∼ 200 m 2 s −2 about a day before B rms reaches a plateau of about 220 G. The energy increase of about ∼ 300 m 2 s −2 seen about three days prior to the AR emergence appears to be indicative of a subsurface concentration of the magnetic field resulting in a rapid growth of B rms in the photosphere.…”

Section: Isolated Arsmentioning

confidence: 99%

HIGH-WAVENUMBER SOLAR f-MODE STRENGTHENING PRIOR TO ACTIVE REGION FORMATION

Singh

Raichur

Brandenburg

2016

ApJ

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We report a systematic strengthening of the local solar surface or fundamental f -mode 1-2 days prior to the emergence of an active region (AR) in the same (corotating) location. Except for a possibly related increase in the kurtosis of the magnetic field, no indication can be seen in the magnetograms at that time. Our study is motivated by earlier numerical findings of Singh et al. (2014) which showed that, in the presence of a nonuniform magnetic field that is concentrated a few scale heights below the surface, the f -mode fans out in the diagnostic kω diagram at high wavenumbers. Here we explore this possibility using data from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory and show for six isolated ARs, 11130, 11158, 11242, 11105, 11072, and 11768, that at large latitudinal wavenumbers (corresponding to horizontal scales of around 3000 km), the f -mode displays strengthening about two days prior to AR formation and thus provides a new precursor for AR formation. Furthermore, we study two ARs, 12051 and 11678, apart from a magnetically quiet patch lying next to AR 12529, to demonstrate the challenges in extracting such a precursor signal when a newly forming AR emerges in a patch that lies in close proximity of one or several already existing ARs which are expected to pollute neighboring patches. We then discuss plausible procedures for extracting precursor signals from regions with crowded environments. The idea that the f -mode is perturbed days before any visible magnetic activity occurs at the surface can be important in constraining dynamo models aimed at understanding the global magnetic activity of the Sun.

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“…The main observing target was AR 11158, which became the first major flaring region of solar cycle 24. The magnetic structure and evolution of this active region as well as the properties of the M-and X-class flares it produced have been studied in a number of papers (e.g., Young et al 2011Young et al , 2013Kosovichev 2011;Schrijver et al 2011;Sun et al 2012;Inoue et al 2013;Sorriso-Valvo et al 2015;Inoue et al 2015;Kuroda et al 2015).…”

Section: Data and Data Reductionmentioning

confidence: 99%

Chromospheric evaporation flows and density changes deduced from Hinode/EIS during an M1.6 flare

Gömöry

Veronig

et al. 2016

A&A

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Aims. We study the response of the solar atmosphere during a GOES M1.6 flare using spectroscopic and imaging observations. In particular, we examine the evolution of the mass flows and electron density together with the energy input derived from hard X-ray (HXR) in the context of chromospheric evaporation.Methods. We analyzed high-cadence sit-and-stare observations acquired with the Hinode/EIS spectrometer in the Fe xiii 202.044 Å (log T = 6.2) and Fe xvi 262.980 Å (log T = 6.4) spectral lines to derive temporal variations of the line intensity, Doppler shifts, and electron density during the flare. We combined these data with HXR measurements acquired with RHESSI to derive the energy input to the lower atmosphere by flare-accelerated electrons.Results. During the flare impulsive phase, we observe no significant flows in the cooler Fe xiii line but strong upflows, up to 80-150 km s −1 , in the hotter Fe xvi line. The largest Doppler shifts observed in the Fe xvi line were co-temporal with the sharp intensity peak. The electron density obtained from a Fe xiii line pair ratio exhibited fast increase (within two minutes) from the pre-flare level of 5.01 × 10 9 cm −3 to 3.16 × 10 10 cm −3 during the flare peak. The nonthermal energy flux density deposited from the coronal acceleration site to the lower atmospheric layers during the flare peak was found to be 1.34 × 10 10 erg s −1 cm −2 for a low-energy cut-off that was estimated to be 16 keV. During the decline flare phase, we found a secondary intensity and density peak of lower amplitude that was preceded by upflows of ∼15 km s −1 that were detected in both lines. The flare was also accompanied by a filament eruption that was partly captured by the EIS observations. We derived Doppler velocities of 250-300 km s −1 for the upflowing filament material. Conclusions. The spectroscopic results for the flare peak are consistent with the scenario of explosive chromospheric evaporation, although a comparatively low value of the nonthermal energy flux density was determined for this phase of the flare. This outcome is discussed in the context of recent hydrodynamic simulations. It provides observational evidence that the response of the atmospheric plasma strongly depends on the properties of the electron beams responsible for the heating, in particular the steepness of the energy distribution. The secondary peak of line intensity and electron density detected during the decline phase is interpreted as a signature of flare loops being filled by expanding hot material that is due to chromospheric evaporation.

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Magnetic Structure Producing X- And M-Class Solar Flares in Solar Active Region 11158

Abstract: We study the three-dimensional magnetic structure of solar active region 11158, which produced one X-class and several M-class flares on 2011 February

Cited by 46 publications

References 51 publications

Magnetohydrodynamic Simulations for Studying Solar Flare Trigger Mechanism

Magnetohydrodynamic Simulations for Studying Solar Flare Trigger Mechanism

HIGH-WAVENUMBER SOLAR f-MODE STRENGTHENING PRIOR TO ACTIVE REGION FORMATION

Chromospheric evaporation flows and density changes deduced from Hinode/EIS during an M1.6 flare

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