Magnetic reconnection in current sheets is a magnetic-to-particle energy conversion process that is fundamental to many space and laboratory plasma systems. In the standard model of reconnection, this process occurs in a minuscule electron-scale diffusion region1,2. On larger scales, ions couple to the newly reconnected magnetic-field lines and are ejected away from the diffusion region in the form of bi-directional ion jets at the ion Alfvén speed3,4,5. Much of the energy conversion occurs in spatially extended ion exhausts downstream of the diffusion region6. In turbulent plasmas, which contain a large number of small-scale current sheets, reconnection has long been suggested to have a major role in the dissipation of turbulent energy at kinetic scales7,8,9,10,11. However, evidence for reconnection plasma jetting in small-scale turbulent plasmas has so far been lacking. Here we report observations made in Earth’s turbulent magnetosheath region (downstream of the bow shock) of an electron-scale current sheet in which diverging bi-directional super-ion-Alfvénic electron jets, parallel electric fields and enhanced magnetic-to-particle energy conversion were detected. Contrary to the standard model of reconnection, the thin reconnecting current sheet was not embedded in a wider ion-scale current layer and no ion jets were detected. Observations of this and other similar, but unidirectional, electron jet events without signatures of ion reconnection reveal a form of reconnection that can drive turbulent energy transfer and dissipation in electron-scale current sheets without ion coupling.
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We are grateful for the dedicated efforts of the MMS team. We thank J. Gosling, who inspired us to search for unconventional reconnection in space. This work was supported by NASA contract number NNG04EB99C at SwRI, which funded work at most of the co-authors’ institutions in the United States. The work at U. C. Berkeley was supported by NASA grants 80NSSC18K0157 and NNX08AO83G. UK involvement at Imperial College was supported by STFC (UK) grant ST/N000692/1. The French involvement (SCM instruments) on MMS is supported by CNES, CNRS-INSIS and CNRS-INSU.
Nature thanks G. Paschmann and the other anonymous reviewer(s) for their contribution to the peer review of this work.