From Coronal Observations to MHD Simulations, the Building Blocks for 3D Models of Solar Flares (Invited Review)

Strong solar flares and coronal mass ejections, here defined not only as the bursts of electromagnetic radiation but as the entire process in which magnetic energy is released through magnetic reconnection and plasma instability, emanate from active regions (ARs) in which high magnetic non-potentiality resides in a wide variety of forms. This review focuses on the formation and evolution of flare-productive ARs from both observational and theoretical points of view. Starting from a general introduction of the genesis of ARs and solar flares, we give an overview of the key observational features during the long-term evolution in the pre-flare state, the rapid changes in the magnetic field associated with the flare occurrence, and the physical mechanisms behind these phenomena. Our picture of flare-productive ARs is summarized as follows: subject to the turbulent convection, the rising magnetic flux in the interior deforms into a complex structure and gains high non-potentiality; as the flux appears on the surface, an AR with large free magnetic energy and helicity is built, which is represented by -sunspots, sheared polarity inversion lines, magnetic flux ropes, etc; the flare occurs when sufficient magnetic energy has accumulated, and the drastic coronal evolution affects magnetic fields even in the photosphere. We show that the improvement of observational instruments and modeling capabilities has significantly advanced our understanding in the last decades. Finally, we discuss the outstanding issues and future perspective and further broaden our scope to the possible applications of our knowledge to space-weather forecasting, extreme events in history, and corresponding stellar activities. Electronic supplementary material The online version of this article (10.1007/s41116-019-0019-7) contains supplementary material, which is available to authorized users.

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“…( 2006 ), Chen ( 2011 ), Shibata and Magara ( 2011 ) and Janvier et al. ( 2015 ) for theoretical and modeling aspects.…”

Section: Active Regions and Solar Flaresmentioning

confidence: 99%

Flare-productive active regions

Toriumi

Wang

2019

Living Rev Sol Phys

247

151

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“…Sudden eruptions on the Sun and solar-type stars occur due to the rapid release of free magnetic energy stored in the sheared and/or twisted strong fields typically associated with sunspots and active regions (e.g. Fletcher et al ., 2011; Shibata and Magara, 2011; Kazachenko et al ., 2012; Janvier et al ., 2015). Large flares are often accompanied by CMEs (Gopalswamy et al ., 2005).…”

Section: Space Weather From Active Starsmentioning

confidence: 99%

Impact of space weather on climate and habitability of terrestrial-type exoplanets

Airapetian

Barnes

Cohen

et al. 2019

International Journal of Astrobiology

193

141

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The search for life in the Universe is a fundamental problem of astrobiology and modern science. The current progress in the detection of terrestrial-type exoplanets has opened a new avenue in the characterization of exoplanetary atmospheres and in the search for biosignatures of life with the upcoming ground-based and space missions. To specify the conditions favourable for the origin, development and sustainment of life as we know it in other worlds, we need to understand the nature of global (astrospheric), and local (atmospheric and surface) environments of exoplanets in the habitable zones (HZs) around G-K-M dwarf stars including our young Sun. Global environment is formed by propagated disturbances from the planet-hosting stars in the form of stellar flares, coronal mass ejections, energetic particles and winds collectively known as astrospheric space weather. Its characterization will help in understanding how an exoplanetary ecosystem interacts with its host star, as well as in the specification of the physical, chemical and biochemical conditions that can create favourable and/or detrimental conditions for planetary climate and habitability along with evolution of planetary internal dynamics over geological timescales. A key linkage of (astro)physical, chemical and geological processes can only be understood in the framework of interdisciplinary studies with the incorporation of progress in heliophysics, astrophysics, planetary and Earth sciences. The assessment of the impacts of host stars on the climate and habitability of terrestrial (exo)planets will significantly expand the current definition of the HZ to the biogenic zone and provide new observational strategies for searching for signatures of life. The major goal of this paper is to describe and discuss the current status and recent progress in this interdisciplinary field in light of presentations and discussions during the NASA Nexus for Exoplanetary System Science funded workshop ‘Exoplanetary Space Weather, Climate and Habitability’ and to provide a new roadmap for the future development of the emerging field of exoplanetary science and astrobiology.

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“…There are several competing models for the initiation of coronal mass ejections and several competing mechanisms for the gradual accumulation of the free magnetic energy necessary for release during the eruption (e.g., see reviews by Klimchuk [], Forbes et al [], Aulanier [], Janvier et al [], and references therein). In general, regardless of the specific ideal or resistive magnetohydrodynamic (MHD) instabilities associated with the rapid transition to a catastrophic, runaway eruption of coronal fields and plasma, essentially every CME model leads to magnetic reconnection at a vertical/radial current sheet that drives the eruption in the manner of the CSHKP eruptive flare scenario [ Carmichael , ; Sturrock , ; Hirayama , ; Kopp and Pneuman , ].…”

Section: Introductionmentioning

confidence: 99%

A model for stealth coronal mass ejections

Lynch

Masson

et al. 2016

JGR Space Physics

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Stealth coronal mass ejections (CMEs) are events in which there are almost no observable signatures of the CME eruption in the low corona but often a well‐resolved slow flux rope CME observed in the coronagraph data. We present results from a three‐dimensional numerical magnetohydrodynamics (MHD) simulation of the 1–2 June 2008 slow streamer blowout CME that Robbrecht et al. (2009) called “the CME from nowhere.” We model the global coronal structure using a 1.4 MK isothermal solar wind and a low‐order potential field source surface representation of the Carrington Rotation 2070 magnetogram synoptic map. The bipolar streamer belt arcade is energized by simple shearing flows applied in the vicinity of the helmet streamer's polarity inversion line. The flows are large scale and impart a shear typical of that expected from the differential rotation. The slow expansion of the energized helmet streamer arcade results in the formation of a radial current sheet. The subsequent onset of expansion‐induced flare reconnection initiates the stealth CME while gradually releasing the stored magnetic energy. We present favorable comparisons between our simulation results and the multiviewpoint SOHO‐LASCO (Large Angle and Spectrometric Coronagraph) and STEREO‐SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) coronagraph observations of the preeruption streamer structure and the initiation and evolution of the stealth streamer blowout CME.

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From Coronal Observations to MHD Simulations, the Building Blocks for 3D Models of Solar Flares (Invited Review)

Cited by 8 publications

References 196 publications

Flare-productive active regions

Flare-productive active regions

Impact of space weather on climate and habitability of terrestrial-type exoplanets

A model for stealth coronal mass ejections

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