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A New Look at the Electron Diffusion Region in Asymmetric Magnetic Reconnection.

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Title: A New Look at the Electron Diffusion Region in Asymmetric Magnetic Reconnection.
Authors: Hesse, Michael1,2,3, Norgren, Cecilia1, Tenfjord, Paul1, Burch, James L.2, Yi-Hsin Liu4, Bessho, Naoki5, Li-Jen Chen6, Shan Wang5, Kolstø, Håkon1, Spinnangr, Susanne F.1, Ergun, Robert E.7, Moretto, Therese1, Kwagala, Norah K.1
Source: Journal of Geophysical Research. Space Physics. Feb2021, Vol. 126 Issue 2, p1-16. 16p.
Subject Terms: *Convection (Meteorology), Electron diffusion, Magnetic reconnection, Magnetic fields, Electron distribution
Abstract: A new look at the structure of the electron diffusion region in collision less magnetic reconnection is presented. The research is based on a particle-in-cell simulation of asymmetric magnetic reconnection, which includes a temperature gradient across the current layer in addition to density and magnetic field gradient. We find that none of X-point, flow stagnation point, and local current density peak coincide. Current and energy balance analyses around the flow stagnation point and current density peak show consistently that current dissipation is associated with the divergence of nongyrotropic electron pressure. Furthermore, the same pressure terms, when combined with shear-type gradients of the electron flow velocity, also serve to maintain local thermal energy against convective losses. These effects are similar to those found also in symmetric magnetic reconnection. In addition, we find here significant effects related to the convection of current, which we can relate to a generalized diamagnetic drift by the nongyrotropic pressure divergence. Therefore, only part of the pressure force serves to dissipate the current density. However, the prior conclusion that the role of the reconnection electric field is to maintain the current density, which was obtained for a symmetric system, applies here as well. Finally, we discuss related features of electron distribution function in the electron diffusion region (EDR). Specifically, we analyze both new crescent substructures as well as outer, higher energy crescents generated by accelerated magnetospheric particles. [ABSTRACT FROM AUTHOR]
Copyright of Journal of Geophysical Research. Space Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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An: 149767928
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PubType: Academic Journal
PubTypeId: academicJournal
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  Data: A New Look at the Electron Diffusion Region in Asymmetric Magnetic Reconnection.
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  Data: <searchLink fieldCode="JN" term="%22Journal+of+Geophysical+Research%2E+Space+Physics%22">Journal of Geophysical Research. Space Physics</searchLink>. Feb2021, Vol. 126 Issue 2, p1-16. 16p.
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  Data: *<searchLink fieldCode="DE" term="%22Convection+%28Meteorology%29%22">Convection (Meteorology)</searchLink><br /><searchLink fieldCode="DE" term="%22Electron+diffusion%22">Electron diffusion</searchLink><br /><searchLink fieldCode="DE" term="%22Magnetic+reconnection%22">Magnetic reconnection</searchLink><br /><searchLink fieldCode="DE" term="%22Magnetic+fields%22">Magnetic fields</searchLink><br /><searchLink fieldCode="DE" term="%22Electron+distribution%22">Electron distribution</searchLink>
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  Data: A new look at the structure of the electron diffusion region in collision less magnetic reconnection is presented. The research is based on a particle-in-cell simulation of asymmetric magnetic reconnection, which includes a temperature gradient across the current layer in addition to density and magnetic field gradient. We find that none of X-point, flow stagnation point, and local current density peak coincide. Current and energy balance analyses around the flow stagnation point and current density peak show consistently that current dissipation is associated with the divergence of nongyrotropic electron pressure. Furthermore, the same pressure terms, when combined with shear-type gradients of the electron flow velocity, also serve to maintain local thermal energy against convective losses. These effects are similar to those found also in symmetric magnetic reconnection. In addition, we find here significant effects related to the convection of current, which we can relate to a generalized diamagnetic drift by the nongyrotropic pressure divergence. Therefore, only part of the pressure force serves to dissipate the current density. However, the prior conclusion that the role of the reconnection electric field is to maintain the current density, which was obtained for a symmetric system, applies here as well. Finally, we discuss related features of electron distribution function in the electron diffusion region (EDR). Specifically, we analyze both new crescent substructures as well as outer, higher energy crescents generated by accelerated magnetospheric particles. [ABSTRACT FROM AUTHOR]
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  Data: <i>Copyright of Journal of Geophysical Research. Space Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
PLink https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=8gh&AN=149767928
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      – Type: doi
        Value: 10.1029/2020JA028456
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      – Code: eng
        Text: English
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      Pagination:
        PageCount: 16
        StartPage: 1
    Subjects:
      – SubjectFull: Convection (Meteorology)
        Type: general
      – SubjectFull: Electron diffusion
        Type: general
      – SubjectFull: Magnetic reconnection
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      – SubjectFull: Magnetic fields
        Type: general
      – SubjectFull: Electron distribution
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      – TitleFull: A New Look at the Electron Diffusion Region in Asymmetric Magnetic Reconnection.
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              Text: Feb2021
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