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Oka M, Birn J, Egedal J, Guo F, Ergun RE, Turner DL, Khotyaintsev Y, Hwang KJ, Cohen IJ, Drake JF. Particle Acceleration by Magnetic Reconnection in Geospace. SPACE SCIENCE REVIEWS 2023; 219:75. [PMID: 37969745 PMCID: PMC10630319 DOI: 10.1007/s11214-023-01011-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 10/05/2023] [Indexed: 11/17/2023]
Abstract
Particles are accelerated to very high, non-thermal energies during explosive energy-release phenomena in space, solar, and astrophysical plasma environments. While it has been established that magnetic reconnection plays an important role in the dynamics of Earth's magnetosphere, it remains unclear how magnetic reconnection can further explain particle acceleration to non-thermal energies. Here we review recent progress in our understanding of particle acceleration by magnetic reconnection in Earth's magnetosphere. With improved resolutions, recent spacecraft missions have enabled detailed studies of particle acceleration at various structures such as the diffusion region, separatrix, jets, magnetic islands (flux ropes), and dipolarization front. With the guiding-center approximation of particle motion, many studies have discussed the relative importance of the parallel electric field as well as the Fermi and betatron effects. However, in order to fully understand the particle acceleration mechanism and further compare with particle acceleration in solar and astrophysical plasma environments, there is a need for further investigation of, for example, energy partition and the precise role of turbulence.
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Affiliation(s)
- Mitsuo Oka
- Space Sciences Laboratory, University of California Berkeley, 7 Gauss Way, Berkeley, 94720 CA USA
| | - Joachim Birn
- Center for Space Plasma Physics, Space Science Institute, 4765 Walnut Street, Boulder, 80301 CO USA
- Los Alamos National Laboratory, Los Alamos, 87545 NM USA
| | - Jan Egedal
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, 53706 WI USA
| | - Fan Guo
- Los Alamos National Laboratory, Los Alamos, 87545 NM USA
| | - Robert E. Ergun
- Laboratory for Atmospheric and Space Physics, University of Colorado, 1234 Innovation Drive, Boulder, 80303 CO USA
- Department of Astrophysical and Planetary Sciences, University of Colorado, 2000 Colorado Avenue, Boulder, 80309 CO USA
| | - Drew L. Turner
- The Johns Hopkins Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, 20723 MD USA
| | | | - Kyoung-Joo Hwang
- Southwest Research Institute, 6220 Culebra Road, San Antonio, 78238 TX USA
| | - Ian J. Cohen
- The Johns Hopkins Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, 20723 MD USA
| | - James F. Drake
- Department of Physics, The Institute for Physical Science and Technology and The Joint Space Science Institute, University of Maryland, College Park, 20742 MD USA
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DuBois AM, Crabtree C, Ganguli G, Malaspina DM, Amatucci WE. MMS Observations of a Compressed Current Sheet: Importance of the Ambipolar Electric Field. PHYSICAL REVIEW LETTERS 2022; 129:105101. [PMID: 36112445 DOI: 10.1103/physrevlett.129.105101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 07/15/2022] [Accepted: 08/12/2022] [Indexed: 06/15/2023]
Abstract
Spacecraft data reveal a nonuniform ambipolar electric field transverse to the magnetic field in a thin current sheet in Earth's magnetotail that leads to intense E×B velocity shear and nongyrotropic particle distributions. The E×B drift far exceeds the diamagnetic drift and thus drives observed lower hybrid waves. The shear-driven waves are localized to the magnetic field reversal region and are therefore ideally suited for the anomalous dissipation necessary for reconnection. It also reveals substructures embedded in the current density, indicating a compressed current sheet.
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Affiliation(s)
- Ami M DuBois
- U.S. Naval Research Laboratory, Plasma Physics Division, Washington, D.C. 20375-5346, USA
| | - Chris Crabtree
- U.S. Naval Research Laboratory, Plasma Physics Division, Washington, D.C. 20375-5346, USA
| | - Gurudas Ganguli
- U.S. Naval Research Laboratory, Plasma Physics Division, Washington, D.C. 20375-5346, USA
| | - David M Malaspina
- Astrophysical and Planetary Sciences Department, University of Colorado, Boulder, Colorado 80303-7814, USA
- Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado 80303-7814, USA
| | - William E Amatucci
- U.S. Naval Research Laboratory, Plasma Physics Division, Washington, D.C. 20375-5346, USA
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Li X, Wang R, Lu Q, Russell CT, Lu S, Cohen IJ, Ergun RE, Wang S. Three-dimensional network of filamentary currents and super-thermal electrons during magnetotail magnetic reconnection. Nat Commun 2022; 13:3241. [PMID: 35688827 PMCID: PMC9187682 DOI: 10.1038/s41467-022-31025-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Accepted: 05/24/2022] [Indexed: 11/24/2022] Open
Abstract
Magnetic reconnection is a fundamental plasma process by which magnetic field lines on two sides of the current sheet flow inward to yield an X-line topology. It is responsible for producing energetic electrons in explosive phenomena in space, astrophysical, and laboratorial plasmas. The X-line region is supposed to be the important place for generating energetic electrons. However, how these energetic electrons are generated in such a limited region is still poorly understood. Here, using Magnetospheric multiscale mission data acquired in Earth’s magnetotail, we present direct evidence of super-thermal electrons up to 300 keV inside an X-line region, and the electrons display a power-law spectrum with an index of about 8.0. Concurrently, three-dimensional network of dynamic filamentary currents in electron scale is observed and leads to electromagnetic turbulence therein. The observations indicate that the electrons are effectively accelerated while the X-line region evolves into turbulence with a complex filamentary current network. Magnetotail reconnection plays an important role in explosive energy conversion. Here, the authors show direct evidence of super-thermal electrons up to 300 keV within X-line region in Earth’s magnetotail, indicating effective electron acceleration due to turbulence.
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Affiliation(s)
- Xinmin Li
- CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Science, University of Science and Technology of China, Hefei, 230026, China.,CAS Center for Excellence in Comparative Planetology, Hefei, China.,Anhui Mengcheng Geophysics National Observation and Research Station, University of Science and Technology of China, Mengcheng, 233500, Anhui, China
| | - Rongsheng Wang
- CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Science, University of Science and Technology of China, Hefei, 230026, China. .,CAS Center for Excellence in Comparative Planetology, Hefei, China. .,Anhui Mengcheng Geophysics National Observation and Research Station, University of Science and Technology of China, Mengcheng, 233500, Anhui, China.
| | - Quanming Lu
- CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Science, University of Science and Technology of China, Hefei, 230026, China. .,CAS Center for Excellence in Comparative Planetology, Hefei, China. .,Anhui Mengcheng Geophysics National Observation and Research Station, University of Science and Technology of China, Mengcheng, 233500, Anhui, China.
| | - Christopher T Russell
- Earth Planetary and Space Sciences, University of California, Los Angeles, CA, 90095, USA
| | - San Lu
- CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Science, University of Science and Technology of China, Hefei, 230026, China.,CAS Center for Excellence in Comparative Planetology, Hefei, China.,Anhui Mengcheng Geophysics National Observation and Research Station, University of Science and Technology of China, Mengcheng, 233500, Anhui, China
| | - Ian J Cohen
- The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | - R E Ergun
- Department for Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO, USA
| | - Shui Wang
- CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Science, University of Science and Technology of China, Hefei, 230026, China.,CAS Center for Excellence in Comparative Planetology, Hefei, China.,Anhui Mengcheng Geophysics National Observation and Research Station, University of Science and Technology of China, Mengcheng, 233500, Anhui, China
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Egedal J, Ng J, Le A, Daughton W, Wetherton B, Dorelli J, Gershman D, Rager A. Pressure Tensor Elements Breaking the Frozen-In Law During Reconnection in Earth's Magnetotail. PHYSICAL REVIEW LETTERS 2019; 123:225101. [PMID: 31868399 DOI: 10.1103/physrevlett.123.225101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 08/22/2019] [Indexed: 06/10/2023]
Abstract
Aided by fully kinetic simulations, spacecraft observations of magnetic reconnection in Earth's magnetotail are analyzed. The structure of the electron diffusion region is in quantitative agreement with the numerical model. Of special interest, the spacecraft data reveal how reconnection is mediated by off-diagonal stress in the electron pressure tensor breaking the frozen-in law of the electron fluid.
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Affiliation(s)
- J Egedal
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J Ng
- Center for Heliophysics, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - A Le
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - W Daughton
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - B Wetherton
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - J Dorelli
- Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
| | - D Gershman
- Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
| | - A Rager
- Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
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Hwang K, Choi E, Dokgo K, Burch JL, Sibeck DG, Giles BL, Goldstein ML, Paterson WR, Pollock CJ, Shi QQ, Fu H, Hasegawa H, Gershman DJ, Khotyaintsev Y, Torbert RB, Ergun RE, Dorelli JC, Avanov L, Russell CT, Strangeway RJ. Electron Vorticity Indicative of the Electron Diffusion Region of Magnetic Reconnection. GEOPHYSICAL RESEARCH LETTERS 2019; 46:6287-6296. [PMID: 31598018 PMCID: PMC6774273 DOI: 10.1029/2019gl082710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 05/08/2019] [Accepted: 05/28/2019] [Indexed: 06/10/2023]
Abstract
While vorticity defined as the curl of the velocity has been broadly used in fluid and plasma physics, this quantity has been underutilized in space physics due to low time resolution observations. We report Magnetospheric Multiscale (MMS) observations of enhanced electron vorticity in the vicinity of the electron diffusion region of magnetic reconnection. On 11 July 2017 MMS traversed the magnetotail current sheet, observing tailward-to-earthward outflow reversal, current-carrying electron jets in the direction along the electron meandering motion or out-of-plane direction, agyrotropic electron distribution functions, and dissipative signatures. At the edge of the electron jets, the electron vorticity increased with magnitudes greater than the electron gyrofrequency. The out-of-plane velocity shear along distance from the current sheet leads to the enhanced vorticity. This, in turn, contributes to the magnetic field perturbations observed by MMS. These observations indicate that electron vorticity can act as a proxy for delineating the electron diffusion region of magnetic reconnection.
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Affiliation(s)
- K.‐J. Hwang
- Southwest Research InstituteSan AntonioTXUSA
| | - E. Choi
- Southwest Research InstituteSan AntonioTXUSA
| | - K. Dokgo
- Southwest Research InstituteSan AntonioTXUSA
| | - J. L. Burch
- Southwest Research InstituteSan AntonioTXUSA
| | | | - B. L. Giles
- NASA Goddard Space Flight CenterGreenbeltMDUSA
| | - M. L. Goldstein
- The Goddard Planetary Heliophysics InstituteUniversity of MarylandBaltimoreMDUSA
| | | | | | - Q. Q. Shi
- School of Earth and Space SciencesPeking UniversityPekingChina
| | - H. Fu
- School of Science and EnvironmentBeihang UniversityBeijingChina
| | - H. Hasegawa
- Institute of Space and Astronautical ScienceJapan Aerospace Exploration AgencySagamiharaJapan
| | | | | | - R. B. Torbert
- Space Science CenterUniversity of New HampshireDurhamNHUSA
| | - R. E. Ergun
- Laboratory for Atmospheric and Space PhysicsUniversity of Colorado BoulderBoulderCOUSA
| | | | - L. Avanov
- NASA Goddard Space Flight CenterGreenbeltMDUSA
- The Goddard Planetary Heliophysics InstituteUniversity of MarylandBaltimoreMDUSA
| | - C. T. Russell
- Institute of Geophysics and Planetary PhysicsUniversity of CaliforniaLos AngelesCAUSA
| | - R. J. Strangeway
- Institute of Geophysics and Planetary PhysicsUniversity of CaliforniaLos AngelesCAUSA
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