TY - JOUR
T1 - Flare-productive active regions
AU - Toriumi, Shin
AU - Wang, Haimin
N1 - Funding Information:
S.T. benefited from fruitful discussions held in the series of Flux Emergence Workshops, the Project for Solar-Terrestrial Environment Prediction (PSTEP), the solar–stellar team sponsored by the International Space Science Institute (ISSI), and Nagoya University ISEE/CICR International Workshop on Data-driven Models. S.T. would like to thank Mark C.M. Cheung, Yuhong Fan, George H. Fisher, Manuel Güdel, Hiroki Kurokawa, Mark G. Linton, Rachel A. Osten, and Takashi Sekii, for providing valuable comments, discussions, and continuous supports. H.W. thanks Chang Liu for his contribution in writing the 2015 RAA review paper that prepared some knowledge for this review. We thank the anonymous referees and the editor Carolus J. Schrijver for very helpful comments. Data are courtesy of the science teams of Hinode, SOHO, and SDO. Hinode is a Japanese mission developed and launched by ISAS/JAXA, with NAOJ as domestic partner and NASA and STFC (UK) as international partners. It is operated by these agencies in cooperation with ESA and NSC (Norway). SOHO is a project of international cooperation between ESA and NASA. HMI and AIA are instruments on board SDO, a mission for NASA’s Living With a Star program. We thank Sian Prosser, the Royal Astronomical Society, for providing the sunspot drawing by Carrington. The work was supported by JSPS KAKENHI Grant Nos. JP16K17671 (PI: S. Toriumi) and JP15H05814 (PI: K. Ichimoto) and by the NINS program for cross-disciplinary study (Grant Nos. 01321802 and 01311904) on Turbulence, Transport, and Heating Dynamics in Laboratory and Solar/Astrophysical Plasmas: “SoLaBo-X”. H.W. acknowledges the support of US NSF under Grant AGS-1821294 and US NASA under Grants 80NSSC17K0016, 80NSSC18K1133, 80NSSC18K1705, and 80NSSC19K0257.
Publisher Copyright:
© 2019, The Author(s).
PY - 2019/12/1
Y1 - 2019/12/1
N2 - 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 δ-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.
AB - 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 δ-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.
KW - Active regions
KW - Dynamics flares
KW - Initiation and propagation flares
KW - Magnetic fields active regions
KW - Models magnetohydrodynamics
KW - Structure coronal mass ejections
UR - http://www.scopus.com/inward/record.url?scp=85066117351&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85066117351&partnerID=8YFLogxK
U2 - 10.1007/s41116-019-0019-7
DO - 10.1007/s41116-019-0019-7
M3 - Review article
AN - SCOPUS:85066117351
SN - 2367-3648
VL - 16
JO - Living Reviews in Solar Physics
JF - Living Reviews in Solar Physics
IS - 1
M1 - 3
ER -