Investigating the Magnetic Imprints of Major Solar Eruptions with SDO/HMI High-cadence Vector Magnetograms

Sun, Xudong; Hoeksema, J. T.; Liu, Yang; Kazachenko, Maria D.; Chen, Ruizhu

doi:10.3847/1538-4357/aa69c1

Cited by 74 publications

(104 citation statements)

References 67 publications

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“…We show that newly emerging ARs gradually transition to flare-productive states prior to their first flares. The Lorentz force was hitherto known to increase significantly only minutes before flares (18). We find, most notably in the emerging ARs before the first flares, evidence of elevated Lorentz forces exerted on the photosphere by magnetic field in the overlying corona for days before flares.…”

Section: Discussionmentioning

confidence: 53%

Machine learning reveals systematic accumulation of electric current in lead-up to solar flares

Dhuri

Hanasoge

Cheung

2019

Proc. Natl. Acad. Sci. U.S.A.

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Solar flares -bursts of high-energy radiation responsible for severe space-weather effects -are a consequence of the occasional destabilization of magnetic fields rooted in active regions (ARs). The complexity of AR evolution is a barrier to a comprehensive understanding of flaring processes and accurate prediction. Though machine learning (ML) has been used to improve flare predictions, the potential for revealing precursors and associated physics has been underexploited. Here, we train ML algorithms to classify between vectormagnetic-field observations from flaring ARs, producing at least one M-/X-class flare, and non-flaring ARs. Analysis of magnetic-field observations accurately classified by the machine presents statistical evidence for (1) ARs persisting in flare-productive states -characterized by AR area -for days, before and after M-and X-class flare events, (2) systematic pre-flare build-up of free energy in the form of electric currents, suggesting that associated subsurface magnetic field is twisted, (3) intensification of Maxwell stresses in the corona above newly emerging ARs, days before first flares. These results provide new insights into flare physics and improving flare forecasting.Solar Flares | Space Weather | Solar Magnetic Fields | Machine Learning

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Section: Discussionmentioning

confidence: 53%

Machine learning reveals systematic accumulation of electric current in lead-up to solar flares

Dhuri

Hanasoge

Cheung

2019

Proc. Natl. Acad. Sci. U.S.A.

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“…The authors formulated the resulted changes of the integrated vertical (downward) and horizontal Lorentz force exerted on the photosphere from the corona, and suggested that the former may energize seismic waves and the latter may cause plasma bulk motions. Thus far, these predictions of the back reaction theory have been substantiated by many aspects of observational results of flare-related photospheric magnetic/flow field changes, including the rapid and permanent step-like increase of horizontal field at flaring PILs (e.g., Wang 1992;Liu et al 2005;Wang et al 2009;Wang & Liu 2010;Liu et al 2012;Sun et al 2012;Petrie 2012;Sun et al 2017), possible linkage to the excitation of seismic waves (e.g., Alvarado-Gómez et al 2012;Liu et al 2014), and sunspot displacement and rotations (e.g., Anwar et al 1993;Wang et al 2014;Liu et al 2016). The downward collapse of coronal current systems presumably due to coronal implosion following flares/CMEs is also corroborated by time sequence of nonlinear force-free field models (e.g., Sun et al 2012;Liu et al 2014) and is reflected in MHD simulations (e.g., Fan 2005Fan , 2010.…”

Section: Introductionmentioning

confidence: 93%

“…′′ 09, and the temporal cadence is 15 s. As for magnetic field, we used 135 second cadence vector magnetograms from HMI's full-disk vector field data product (Hoeksema et al 2014;Sun et al 2017), which is provided by the Joint Science Operations Center. The pixel scale of HMI data is 0.…”

Section: Observations and Data Processingmentioning

confidence: 99%

Evolution of Photospheric Flow and Magnetic Fields Associated with the 2015 June 22 M6.5 Flare

Wang

Liu

Deng

et al. 2018

ApJ

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The evolution of photospheric flow and magnetic fields before and after flares can provide important information regarding the flare triggering and back reaction processes. However, such studies on the flow field are rare due to the paucity of highresolution observations covering the entire flaring period. Here we study the structural evolution of penumbra and shear flows associated with the 2015 June 22 M6.5 flare in NOAA AR 12371, using high-resolution imaging observation in the TiO band taken by the 1.6 m Goode Solar Telescope at Big Bear Solar Observatory, with the aid of the differential affine velocity estimator method for flow tracking. The accompanied photospheric vector magnetic field changes are also analyzed using data from the Helioseismic and Magnetic Imager. As a result, we found, for a penumbral segment in the negative field adjacent to the magnetic polarity inversion line (PIL), an enhancement of penumbral flows (up to an unusually high value of ∼2 km s ) and extension of penumbral fibrils after the first peak of the flare hard X-ray (HXR) emission. We also found an area at the PIL, which is co-spatial with a precursor brightening kernel, exhibits a gradual increase of shear flow velocity (up to ∼0.9 km s −1 ) after the flare. The enhancing penumbral and shear flow regions are also accompanied by an increase of horizontal field and decrease of magnetic inclination angle(measured from the solar surface). These results are discussed in the context of the theory of back reaction of coronal restructuring on the photosphere as a result of flare energy release.

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“…The component of the horizontal magnetic field parallel to the PIL also increases during the flare, while the perpendicular component of B h undergoes only minor changes (Sun et al 2012;Petrie 2013). On the contrary, Petrie (2013) and Sun et al (2017) suggest that the vertical magnetic field around the PIL is almost constant with time. Moreover, the chromospheric line-of-sight magnetic field (B los ) obtained for the first time by Kleint (2017) shows that the chromospheric magnetic field decreases nearby the PIL.…”

Section: Introductionmentioning

confidence: 94%

Flare Reconnection-driven Magnetic Field and Lorentz Force Variations at the Sun’s Surface

Barczynski¹,

Aulanier²,

Masson³

et al. 2019

ApJ

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During eruptive flares, vector magnetograms show increasing horizontal magnetic field and downward Lorentz force in the Sun's photosphere around the polarity-inversion line. Such behavior has often been associated with the implosion conjecture and interpreted as the result of either momentum conservation while the eruption moves upward, or of the contraction of flare loops. We characterize the physical origin of these observed behaviors by analyzing a generic 3D MHD simulation of an eruptive flare. Even though the simulation was undesigned to recover the magnetic field and Lorentz force properties, it is fully consistent with them, and it provides key additional informations to understand them. The area where the magnetic field increases gradually develops between current ribbons, which spread away from each other and are connected to the coronal region. This area is merely the footprint of the coronal postflare loops, whose contraction increases their shear field component and the magnetic energy density in line with the ideal induction equation. For simulated data, we computed the Lorentz force density map by applying the method used in observations. We obtained increase of the downward component of the Lorentz force density around the PIL -consistent with observations. However, this significantly differs from the Lorentz force density maps obtained directly from the 3D magnetic field and current. These results altogether question previous interpretations based on the implosion conjecture and momentum conservation with the CME, and rather imply that the observed increases in photospheric horizontal magnetic fields result from the reconnection-driven contraction of sheared flare-loops.

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Investigating the Magnetic Imprints of Major Solar Eruptions with SDO/HMI High-cadence Vector Magnetograms

Cited by 74 publications

References 67 publications

Machine learning reveals systematic accumulation of electric current in lead-up to solar flares

Machine learning reveals systematic accumulation of electric current in lead-up to solar flares

Evolution of Photospheric Flow and Magnetic Fields Associated with the 2015 June 22 M6.5 Flare

Flare Reconnection-driven Magnetic Field and Lorentz Force Variations at the Sun’s Surface

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