Electron-only reconnection and associated electron heating and acceleration in PHASMA
Electron-only reconnection and associated electron heating and acceleration in PHASMA
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DOI：
10.1063/5.0082633
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发表时间：
2022-03
影响因子：
2.2
通讯作者：
P. Shi;P. Srivastav;M. H. Barbhuiya;P. Cassak;E. Scime;M. Swisdak;C. Beatty;T. Gilbert;R. John;M. Lazo;R. Nirwan;Mitchell Paul;E. Scime;K. Stevenson;T. Steinberger
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文献类型：
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作者：
P. Shi;P. Srivastav;M. H. Barbhuiya;P. Cassak;E. Scime;M. Swisdak;C. Beatty;T. Gilbert;R. John;M. Lazo;R. Nirwan;Mitchell Paul;E. Scime;K. Stevenson;T. Steinberger
利用非相干汤姆逊散射，研究了相空间映射（PHASMA）装置中电子重联过程中电子在电子速度分布函数（EVDF）水平上的加热和加速。在两根无扭结焊剂绳合并时产生重连。推式和拉式重连都发生在一次放电中。电子加热局限于分离矩阵周围，电子温度随着离x线的距离沿分离矩阵不断升高。局部测量的焓通量增益可达入射波印亭通量的70%。值得注意的是，在纯电子重联过程中，直接测量了由热体种群和冷束组成的非麦克斯韦evdf。电子束速度与电子alfvsamn速度相当，并与之成比例，揭示了仅由电子重连引起的电子加速特征。在x点两侧的反向电子束的观察提供了“确凿的”证据，证明在PHASMA中只发生电子重连。二维细胞内粒子模拟与实验室测量结果吻合良好。测量到的坡因廷通量到电子焓的转换与最近观测到的磁鞘中仅电子重联一致[Phan等人，Nature 557, 202(2018)]，在与实验相似的无量纲参数下。通过直接解析电子温度增益，实验室测量超出了磁鞘观测。
Using incoherent Thomson scattering, electron heating and acceleration at the electron velocity distribution function (EVDF) level are investigated during electron-only reconnection in the PHAse Space MApping (PHASMA) facility. Reconnection arises during the merger of two kink-free flux ropes. Both push and pull type reconnection occur in a single discharge. Electron heating is localized around the separatrix, and the electron temperature increases continuously along the separatrix with distance from the X-line. The local measured gain in enthalpy flux is up to 70% of the incoming Poynting flux. Notably, non-Maxwellian EVDFs comprised of a warm bulk population and a cold beam are directly measured during the electron-only reconnection. The electron beam velocity is comparable to, and scales with, electron Alfvén speed, revealing the signature of electron acceleration caused by electron-only reconnection. The observation of oppositely directed electron beams on either side of the X-point provides “smoking-gun” evidence of the occurrence of electron-only reconnection in PHASMA. 2D particle-in-cell simulations agree well with the laboratory measurements. The measured conversion of Poynting flux into electron enthalpy is consistent with recent observations of electron-only reconnection in the magnetosheath [Phan et al., Nature 557, 202 (2018)] at similar dimensionless parameters as in the experiments. The laboratory measurements go beyond the magnetosheath observations by directly resolving the electron temperature gain.