Electron heating and energy inventory during asymmetric reconnection in a laboratory plasma
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- Princeton Plasma Physics Laboratory Princeton New Jersey USA
- National Fusion Research Institute Daejeon South Korea
- Space Science Institute Boulder Colorado USA
- Space Science Center University of New Hampshire Durham New Hampshire USA
- Department of Astronomy University of Maryland College Park Maryland USA
Abstract Electron heating and the energy inventory during asymmetric reconnection are studied in the laboratory plasma with a density ratio of about 8 across the current sheet. Features of asymmetric reconnection such as the large density gradients near the low‐density side separatrices, asymmetric in‐plane electric field, and bipolar out‐of‐plane magnetic field are observed. Unlike the symmetric case, electrons are also heated near the low‐density side separatrices. The measured parallel electric field may explain the observed electron heating. Although large fluctuations driven by lower hybrid drift instabilities are also observed near the low‐density side separatrices, laboratory measurements and numerical simulations reported here suggest that they do not play a major role in electron energization. The average electron temperature increase in the exhaust region is proportional to the incoming magnetic energy per an electron/ion pair but exceeds scalings of the previous space observations. This discrepancy is explained by differences in the boundary condition and system size. The profile of electron energy gain from the electric field shows that there is additional electron energy gain associated with the electron diamagnetic current besides a large energy gain near the X line. This additional energy gain increases electron enthalpy, not the electron temperature. Finally, a quantitative analysis of the energy inventory during asymmetric reconnection is conducted. Unlike the symmetric case where the ion energy gain is about twice more than the electron energy gain, electrons and ions obtain a similar amount of energy during asymmetric reconnection.
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- AC0209CH11466
- OSTI ID:
- 1389146
- Journal Information:
- Journal of Geophysical Research. Space Physics, Journal Name: Journal of Geophysical Research. Space Physics Vol. 122 Journal Issue: 9; ISSN 2169-9380
- Publisher:
- American Geophysical Union (AGU)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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