The Acceleration and Confinement of Energetic Electrons by a Termination Shock in a Magnetic Trap: An Explanation for Nonthermal Loop-top Sources during Solar Flares

Xiangliang Kong; Fan Guo; Chengcai Shen; Bin Chen; Yao Chen; Sophie Musset; Lindsay Glesener; Peera Pongkitiwanichakul; Joe Giacalone

doi:10.3847/2041-8213/ab5f67

The Acceleration and Confinement of Energetic Electrons by a Termination Shock in a Magnetic Trap: An Explanation for Nonthermal Loop-top Sources during Solar Flares

Xiangliang Kong, Fan Guo, Chengcai Shen, Bin Chen, Yao Chen, Sophie Musset, Lindsay Glesener, Peera Pongkitiwanichakul, Joe Giacalone

Physics and Astronomy (Twin Cities)

Research output: Contribution to journal › Article › peer-review

30 Scopus citations

Abstract

Nonthermal loop-top sources in solar flares are the most prominent observational signatures that suggest energy release and particle acceleration in the solar corona. Although several scenarios for particle acceleration have been proposed, the origin of the loop-top sources remains unclear. Here we present a model that combines a large-scale magnetohydrodynamic simulation of a two-ribbon flare with a particle acceleration and transport model for investigating electron acceleration by a fast-mode termination shock (TS) at the loop top. Our model provides spatially resolved electron distribution that evolves in response to the dynamic flare geometry. We find a concave-downward magnetic structure located below the flare TS, induced by the fast reconnection downflows. It acts as a magnetic trap to confine the electrons at the loop top for an extended period of time. The electrons are energized significantly as they cross the shock front, and eventually build up a power-law energy spectrum extending to hundreds of kiloelectron volts. We suggest that this particle acceleration and transport scenario driven by a flare TS is a viable interpretation for the observed nonthermal loop-top sources.

Original language	English (US)
Article number	L37
Journal	Astrophysical Journal Letters
Volume	887
Issue number	2
DOIs	https://doi.org/10.3847/2041-8213/ab5f67
State	Published - Dec 20 2019

Bibliographical note

Funding Information:
Xiangliang Kong Fan Guo Chengcai Shen Bin Chen Yao Chen Sophie Musset Lindsay Glesener Peera Pongkitiwanichakul Joe Giacalone Xiangliang Kong Fan Guo Chengcai Shen Bin Chen Yao Chen Sophie Musset Lindsay Glesener Peera Pongkitiwanichakul Joe Giacalone Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, and Institute of Space Sciences, Shandong University, Weihai, Shandong 264209, People’s Republic of China State Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China Los Alamos National Laboratory, Los Alamos, NM 87545, USA New Mexico Consortium, 4200 West Jemez Road, Los Alamos, NM 87544, USA Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Dr. Martin Luther King Boulevard, Newark, NJ 07102, USA School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721, USA Xiangliang Kong (孔祥良), Fan Guo (郭帆), Chengcai Shen (沈呈彩), Bin Chen (陈彬), Yao Chen (陈耀), Sophie Musset, Lindsay Glesener, Peera Pongkitiwanichakul and Joe Giacalone 2019-12-20 2019-12-20 14:47:10 cgi/release: Article released bin/incoming: New from .zip Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence . Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. yes Nonthermal loop-top sources in solar flares are the most prominent observational signatures that suggest energy release and particle acceleration in the solar corona. Although several scenarios for particle acceleration have been proposed, the origin of the loop-top sources remains unclear. Here we present a model that combines a large-scale magnetohydrodynamic simulation of a two-ribbon flare with a particle acceleration and transport model for investigating electron acceleration by a fast-mode termination shock (TS) at the loop top. Our model provides spatially resolved electron distribution that evolves in response to the dynamic flare geometry. We find a concave-downward magnetic structure located below the flare TS, induced by the fast reconnection downflows. It acts as a magnetic trap to confine the electrons at the loop top for an extended period of time. The electrons are energized significantly as they cross the shock front, and eventually build up a power-law energy spectrum extending to hundreds of kiloelectron volts. We suggest that this particle acceleration and transport scenario driven by a flare TS is a viable interpretation for the observed nonthermal loop-top sources. � 2019 The Author(s). Published by the American Astronomical Society. Aschwanden M. J., Caspi A., Cohen C. M. S. et al 2017 ApJ 836 17 10.3847/1538-4357/836/1/17 Aschwanden M. J., Caspi A., Cohen C. M. S. et al ApJ 0004-637X 836 1 17 2017 17 Benz A. O. 2017 LRSP 14 2 10.1007/s41116-016-0004-3 Benz A. O. LRSP 14 2017 2 Chen B., Bastian T. S., Shen C. et al 2015 Sci 350 1238 10.1126/science.aac8467 Chen B., Bastian T. S., Shen C. et al Sci 350 2015 1238 Chen B., Shen C., Reeves K. 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Kong, X., Guo, F., Shen, C., Chen, B., Chen, Y., Musset, S., Glesener, L., Pongkitiwanichakul, P., & Giacalone, J. (2019). The Acceleration and Confinement of Energetic Electrons by a Termination Shock in a Magnetic Trap: An Explanation for Nonthermal Loop-top Sources during Solar Flares. Astrophysical Journal Letters, 887(2), Article L37. https://doi.org/10.3847/2041-8213/ab5f67

Kong, X, Guo, F, Shen, C, Chen, B, Chen, Y, Musset, S, Glesener, L, Pongkitiwanichakul, P & Giacalone, J 2019, 'The Acceleration and Confinement of Energetic Electrons by a Termination Shock in a Magnetic Trap: An Explanation for Nonthermal Loop-top Sources during Solar Flares', Astrophysical Journal Letters, vol. 887, no. 2, L37. https://doi.org/10.3847/2041-8213/ab5f67

@article{fa797a68ebf540d5ac276d5b2b88bbcc,

title = "The Acceleration and Confinement of Energetic Electrons by a Termination Shock in a Magnetic Trap: An Explanation for Nonthermal Loop-top Sources during Solar Flares",

abstract = "Nonthermal loop-top sources in solar flares are the most prominent observational signatures that suggest energy release and particle acceleration in the solar corona. Although several scenarios for particle acceleration have been proposed, the origin of the loop-top sources remains unclear. Here we present a model that combines a large-scale magnetohydrodynamic simulation of a two-ribbon flare with a particle acceleration and transport model for investigating electron acceleration by a fast-mode termination shock (TS) at the loop top. Our model provides spatially resolved electron distribution that evolves in response to the dynamic flare geometry. We find a concave-downward magnetic structure located below the flare TS, induced by the fast reconnection downflows. It acts as a magnetic trap to confine the electrons at the loop top for an extended period of time. The electrons are energized significantly as they cross the shock front, and eventually build up a power-law energy spectrum extending to hundreds of kiloelectron volts. We suggest that this particle acceleration and transport scenario driven by a flare TS is a viable interpretation for the observed nonthermal loop-top sources.",

author = "Xiangliang Kong and Fan Guo and Chengcai Shen and Bin Chen and Yao Chen and Sophie Musset and Lindsay Glesener and Peera Pongkitiwanichakul and Joe Giacalone",

note = "Funding Information: Xiangliang Kong Fan Guo Chengcai Shen Bin Chen Yao Chen Sophie Musset Lindsay Glesener Peera Pongkitiwanichakul Joe Giacalone Xiangliang Kong Fan Guo Chengcai Shen Bin Chen Yao Chen Sophie Musset Lindsay Glesener Peera Pongkitiwanichakul Joe Giacalone Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, and Institute of Space Sciences, Shandong University, Weihai, Shandong 264209, People{\textquoteright}s Republic of China State Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100190, People{\textquoteright}s Republic of China Los Alamos National Laboratory, Los Alamos, NM 87545, USA New Mexico Consortium, 4200 West Jemez Road, Los Alamos, NM 87544, USA Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Dr. Martin Luther King Boulevard, Newark, NJ 07102, USA School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721, USA Xiangliang Kong (孔祥良), Fan Guo (郭帆), Chengcai Shen (沈呈彩), Bin Chen (陈彬), Yao Chen (陈耀), Sophie Musset, Lindsay Glesener, Peera Pongkitiwanichakul and Joe Giacalone 2019-12-20 2019-12-20 14:47:10 cgi/release: Article released bin/incoming: New from .zip Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence . Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. yes Nonthermal loop-top sources in solar flares are the most prominent observational signatures that suggest energy release and particle acceleration in the solar corona. Although several scenarios for particle acceleration have been proposed, the origin of the loop-top sources remains unclear. Here we present a model that combines a large-scale magnetohydrodynamic simulation of a two-ribbon flare with a particle acceleration and transport model for investigating electron acceleration by a fast-mode termination shock (TS) at the loop top. Our model provides spatially resolved electron distribution that evolves in response to the dynamic flare geometry. We find a concave-downward magnetic structure located below the flare TS, induced by the fast reconnection downflows. It acts as a magnetic trap to confine the electrons at the loop top for an extended period of time. The electrons are energized significantly as they cross the shock front, and eventually build up a power-law energy spectrum extending to hundreds of kiloelectron volts. We suggest that this particle acceleration and transport scenario driven by a flare TS is a viable interpretation for the observed nonthermal loop-top sources. � 2019 The Author(s). Published by the American Astronomical Society. Aschwanden M. J., Caspi A., Cohen C. M. S. et al 2017 ApJ 836 17 10.3847/1538-4357/836/1/17 Aschwanden M. J., Caspi A., Cohen C. M. S. et al ApJ 0004-637X 836 1 17 2017 17 Benz A. O. 2017 LRSP 14 2 10.1007/s41116-016-0004-3 Benz A. O. LRSP 14 2017 2 Chen B., Bastian T. S., Shen C. et al 2015 Sci 350 1238 10.1126/science.aac8467 Chen B., Bastian T. S., Shen C. et al Sci 350 2015 1238 Chen B., Shen C., Reeves K. 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ApJ 0004-637X 869 2 116 2018 116 Shibata K. and Magara T. 2011 LRSP 8 6 10.12942/lrsp-2011-6 Shibata K. and Magara T. LRSP 8 2011 6 Sim{\~o}es P. J. A. and Kontar E. P. 2013 A&A 551 A135 10.1051/0004-6361/201220304 Sim{\~o}es P. J. A. and Kontar E. P. A&A 0004-6361 551 2013 A135 Stone J. M., Gardiner T. A., Teuben P., Hawley J. F. and Simon J. B. 2008 ApJS 178 137 10.1086/588755 Stone J. M., Gardiner T. A., Teuben P., Hawley J. F. and Simon J. B. ApJS 0067-0049 178 1 137 2008 137 Sun J., Gao X., Lu Q. and Wang S. 2019 Ap&SS 364 116 10.1007/s10509-019-3610-4 Sun J., Gao X., Lu Q. and Wang S. Ap&SS 0004-640X 364 2019 116 Takahashi T., Qiu J. and Shibata K. 2017 ApJ 848 102 10.3847/1538-4357/aa8f97 Takahashi T., Qiu J. and Shibata K. ApJ 0004-637X 848 2 102 2017 102 Takasao S., Matsumoto T., Nakamura N. and Shibata K. 2015 ApJ 805 135 10.1088/0004-637X/805/2/135 Takasao S., Matsumoto T., Nakamura N. and Shibata K. ApJ 0004-637X 805 2 135 2015 135 Takasao S. and Shibata K. 2016 ApJ 823 150 10.3847/0004-637X/823/2/150 Takasao S. and Shibata K. ApJ 0004-637X 823 2 150 2016 150 Tsuneta S. and Naito T. 1998 ApJL 495 L67 10.1086/311207 Tsuneta S. and Naito T. ApJL 0004-637X 495 1998 L67 Wu C. S. 1984 JGR 89 8857 10.1029/JA089iA10p08857 Wu C. S. JGR 0148-0227 89 1984 8857 Yokoyama T. and Shibata K. 1998 ApJL 494 L113 10.1086/311174 Yokoyama T. and Shibata K. ApJL 0004-637X 494 1998 L113 Yokoyama T. and Shibata K. 2001 ApJ 549 1160 10.1086/319440 Yokoyama T. and Shibata K. ApJ 0004-637X 549 2 1160 2001 1160 Publisher Copyright: {\textcopyright} 2019 The Author(s). Published by the American Astronomical Society..",

year = "2019",

month = dec,

day = "20",

doi = "10.3847/2041-8213/ab5f67",

language = "English (US)",

volume = "887",

journal = "Astrophysical Journal Letters",

issn = "2041-8205",

publisher = "IOP Publishing Ltd.",

number = "2",

}

TY - JOUR

T1 - The Acceleration and Confinement of Energetic Electrons by a Termination Shock in a Magnetic Trap

T2 - An Explanation for Nonthermal Loop-top Sources during Solar Flares

AU - Kong, Xiangliang

AU - Guo, Fan

AU - Shen, Chengcai

AU - Chen, Bin

AU - Chen, Yao

AU - Musset, Sophie

AU - Glesener, Lindsay

AU - Pongkitiwanichakul, Peera

AU - Giacalone, Joe

N1 - Funding Information: Xiangliang Kong Fan Guo Chengcai Shen Bin Chen Yao Chen Sophie Musset Lindsay Glesener Peera Pongkitiwanichakul Joe Giacalone Xiangliang Kong Fan Guo Chengcai Shen Bin Chen Yao Chen Sophie Musset Lindsay Glesener Peera Pongkitiwanichakul Joe Giacalone Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, and Institute of Space Sciences, Shandong University, Weihai, Shandong 264209, People’s Republic of China State Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China Los Alamos National Laboratory, Los Alamos, NM 87545, USA New Mexico Consortium, 4200 West Jemez Road, Los Alamos, NM 87544, USA Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Dr. Martin Luther King Boulevard, Newark, NJ 07102, USA School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721, USA Xiangliang Kong (孔祥良), Fan Guo (郭帆), Chengcai Shen (沈呈彩), Bin Chen (陈彬), Yao Chen (陈耀), Sophie Musset, Lindsay Glesener, Peera Pongkitiwanichakul and Joe Giacalone 2019-12-20 2019-12-20 14:47:10 cgi/release: Article released bin/incoming: New from .zip Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence . Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. yes Nonthermal loop-top sources in solar flares are the most prominent observational signatures that suggest energy release and particle acceleration in the solar corona. Although several scenarios for particle acceleration have been proposed, the origin of the loop-top sources remains unclear. Here we present a model that combines a large-scale magnetohydrodynamic simulation of a two-ribbon flare with a particle acceleration and transport model for investigating electron acceleration by a fast-mode termination shock (TS) at the loop top. Our model provides spatially resolved electron distribution that evolves in response to the dynamic flare geometry. We find a concave-downward magnetic structure located below the flare TS, induced by the fast reconnection downflows. It acts as a magnetic trap to confine the electrons at the loop top for an extended period of time. The electrons are energized significantly as they cross the shock front, and eventually build up a power-law energy spectrum extending to hundreds of kiloelectron volts. We suggest that this particle acceleration and transport scenario driven by a flare TS is a viable interpretation for the observed nonthermal loop-top sources. � 2019 The Author(s). Published by the American Astronomical Society. Aschwanden M. J., Caspi A., Cohen C. M. S. et al 2017 ApJ 836 17 10.3847/1538-4357/836/1/17 Aschwanden M. J., Caspi A., Cohen C. M. S. et al ApJ 0004-637X 836 1 17 2017 17 Benz A. O. 2017 LRSP 14 2 10.1007/s41116-016-0004-3 Benz A. O. LRSP 14 2017 2 Chen B., Bastian T. S., Shen C. et al 2015 Sci 350 1238 10.1126/science.aac8467 Chen B., Bastian T. S., Shen C. et al Sci 350 2015 1238 Chen B., Shen C., Reeves K. 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ApJ 0004-637X 767 2 168 2013 168 Liu W., Petrosian V., Dennis B. R. and Jiang Y. W. 2008 ApJ 676 704 10.1086/527538 Liu W., Petrosian V., Dennis B. R. and Jiang Y. W. ApJ 0004-637X 676 1 704 2008 704 Magara T., Mineshige S., Yokoyama T. and Shibata K. 1996 ApJ 466 1054 10.1086/177575 Magara T., Mineshige S., Yokoyama T. and Shibata K. ApJ 466 1996 1054 Mann G., Warmuth A. and Aurass H. 2009 A&A 494 669 10.1051/0004-6361:200810099 Mann G., Warmuth A. and Aurass H. A&A 0004-6361 494 2009 669 Masuda S., Kosugi T., Hara H., Tsuneta S. and Ogawara Y. 1994 Natur 371 495 10.1038/371495a0 Masuda S., Kosugi T., Hara H., Tsuneta S. and Ogawara Y. Natur 371 1994 495 McLaughlin J. A., Nakariakov V. M., Dominique M., Jelínek P. and Takasao S. 2018 SSRv 214 45 10.1007/s11214-018-0478-5 McLaughlin J. A., Nakariakov V. M., Dominique M., Jelínek P. and Takasao S. SSRv 214 2018 45 Melnikov V. F., Shibasaki K. and Reznikova V. E. 2002 ApJL 580 L185 10.1086/345587 Melnikov V. F., Shibasaki K. and Reznikova V. E. ApJL 0004-637X 580 2002 L185 Miller J. A., Cargill P. J., Emslie A. G. et al 1997 JGR 102 14631 10.1029/97JA00976 Miller J. A., Cargill P. J., Emslie A. G. et al JGR 0148-0227 102 1997 14631 Miller J. A., Larosa T. N. and Moore R. L. 1996 ApJ 461 445 10.1086/177072 Miller J. A., Larosa T. N. and Moore R. L. ApJ 461 1996 445 Musset S., Kontar E. P. and Vilmer N. 2018 A&A 610 A6 10.1051/0004-6361/201731514 Musset S., Kontar E. P. and Vilmer N. A&A 0004-6361 610 2018 A6 Nakariakov V. M. and Melnikov V. F. 2009 SSRv 149 119 10.1007/s11214-009-9536-3 Nakariakov V. M. and Melnikov V. F. SSRv 149 2009 119 Oka M., Birn J., Battaglia M. et al 2018 SSRv 214 82 10.1007/s11214-018-0515-4 Oka M., Birn J., Battaglia M. et al SSRv 214 2018 82 Oka M., Krucker S., Hudson H. S. and Saint-Hilaire P. 2015 ApJ 799 129 10.1088/0004-637X/799/2/129 Oka M., Krucker S., Hudson H. S. and Saint-Hilaire P. ApJ 0004-637X 799 2 129 2015 129 Oka M., Phan T. D., Krucker S. et al 2010 ApJ 714 915 10.1088/0004-637X/714/1/915 Oka M., Phan T. D., Krucker S. et al ApJ 0004-637X 714 1 915 2010 915 Parker E. N. 1965 P&SS 13 9 10.1016/0032-0633(65)90131-5 Parker E. N. P&SS 0032-0633 13 1965 9 Pesce-Rollins M., Omodei N., Petrosian V. et al 2015 ApJL 805 L15 10.1088/2041-8205/805/2/L15 Pesce-Rollins M., Omodei N., Petrosian V. et al ApJL 0004-637X 805 2015 L15 Petrosian V. and Liu S. 2004 ApJ 610 550 10.1086/421486 Petrosian V. and Liu S. ApJ 0004-637X 610 1 550 2004 550 Pongkitiwanichakul P. and Chandran B. D. G. 2014 ApJ 796 45 10.1088/0004-637X/796/1/45 Pongkitiwanichakul P. and Chandran B. D. G. ApJ 0004-637X 796 1 45 2014 45 Seaton D. B. and Forbes T. G. 2009 ApJ 701 348 10.1088/0004-637X/701/1/348 Seaton D. B. and Forbes T. G. ApJ 0004-637X 701 1 348 2009 348 Shen C., Kong X., Guo F., Raymond J. C. and Chen B. 2018 ApJ 869 116 10.3847/1538-4357/aaeed3 Shen C., Kong X., Guo F., Raymond J. C. and Chen B. ApJ 0004-637X 869 2 116 2018 116 Shibata K. and Magara T. 2011 LRSP 8 6 10.12942/lrsp-2011-6 Shibata K. and Magara T. LRSP 8 2011 6 Simões P. J. A. and Kontar E. P. 2013 A&A 551 A135 10.1051/0004-6361/201220304 Simões P. J. A. and Kontar E. P. A&A 0004-6361 551 2013 A135 Stone J. M., Gardiner T. A., Teuben P., Hawley J. F. and Simon J. B. 2008 ApJS 178 137 10.1086/588755 Stone J. M., Gardiner T. A., Teuben P., Hawley J. F. and Simon J. B. ApJS 0067-0049 178 1 137 2008 137 Sun J., Gao X., Lu Q. and Wang S. 2019 Ap&SS 364 116 10.1007/s10509-019-3610-4 Sun J., Gao X., Lu Q. and Wang S. Ap&SS 0004-640X 364 2019 116 Takahashi T., Qiu J. and Shibata K. 2017 ApJ 848 102 10.3847/1538-4357/aa8f97 Takahashi T., Qiu J. and Shibata K. ApJ 0004-637X 848 2 102 2017 102 Takasao S., Matsumoto T., Nakamura N. and Shibata K. 2015 ApJ 805 135 10.1088/0004-637X/805/2/135 Takasao S., Matsumoto T., Nakamura N. and Shibata K. ApJ 0004-637X 805 2 135 2015 135 Takasao S. and Shibata K. 2016 ApJ 823 150 10.3847/0004-637X/823/2/150 Takasao S. and Shibata K. ApJ 0004-637X 823 2 150 2016 150 Tsuneta S. and Naito T. 1998 ApJL 495 L67 10.1086/311207 Tsuneta S. and Naito T. ApJL 0004-637X 495 1998 L67 Wu C. S. 1984 JGR 89 8857 10.1029/JA089iA10p08857 Wu C. S. JGR 0148-0227 89 1984 8857 Yokoyama T. and Shibata K. 1998 ApJL 494 L113 10.1086/311174 Yokoyama T. and Shibata K. ApJL 0004-637X 494 1998 L113 Yokoyama T. and Shibata K. 2001 ApJ 549 1160 10.1086/319440 Yokoyama T. and Shibata K. ApJ 0004-637X 549 2 1160 2001 1160 Publisher Copyright: © 2019 The Author(s). Published by the American Astronomical Society..

PY - 2019/12/20

Y1 - 2019/12/20

N2 - Nonthermal loop-top sources in solar flares are the most prominent observational signatures that suggest energy release and particle acceleration in the solar corona. Although several scenarios for particle acceleration have been proposed, the origin of the loop-top sources remains unclear. Here we present a model that combines a large-scale magnetohydrodynamic simulation of a two-ribbon flare with a particle acceleration and transport model for investigating electron acceleration by a fast-mode termination shock (TS) at the loop top. Our model provides spatially resolved electron distribution that evolves in response to the dynamic flare geometry. We find a concave-downward magnetic structure located below the flare TS, induced by the fast reconnection downflows. It acts as a magnetic trap to confine the electrons at the loop top for an extended period of time. The electrons are energized significantly as they cross the shock front, and eventually build up a power-law energy spectrum extending to hundreds of kiloelectron volts. We suggest that this particle acceleration and transport scenario driven by a flare TS is a viable interpretation for the observed nonthermal loop-top sources.

AB - Nonthermal loop-top sources in solar flares are the most prominent observational signatures that suggest energy release and particle acceleration in the solar corona. Although several scenarios for particle acceleration have been proposed, the origin of the loop-top sources remains unclear. Here we present a model that combines a large-scale magnetohydrodynamic simulation of a two-ribbon flare with a particle acceleration and transport model for investigating electron acceleration by a fast-mode termination shock (TS) at the loop top. Our model provides spatially resolved electron distribution that evolves in response to the dynamic flare geometry. We find a concave-downward magnetic structure located below the flare TS, induced by the fast reconnection downflows. It acts as a magnetic trap to confine the electrons at the loop top for an extended period of time. The electrons are energized significantly as they cross the shock front, and eventually build up a power-law energy spectrum extending to hundreds of kiloelectron volts. We suggest that this particle acceleration and transport scenario driven by a flare TS is a viable interpretation for the observed nonthermal loop-top sources.

UR - http://www.scopus.com/inward/record.url?scp=85077723432&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85077723432&partnerID=8YFLogxK

U2 - 10.3847/2041-8213/ab5f67

DO - 10.3847/2041-8213/ab5f67

M3 - Article

AN - SCOPUS:85077723432

SN - 2041-8205

VL - 887

JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

IS - 2

M1 - L37

ER -

The Acceleration and Confinement of Energetic Electrons by a Termination Shock in a Magnetic Trap: An Explanation for Nonthermal Loop-top Sources during Solar Flares

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