Electron-Scale Current Sheets Observed by MMS in the Plasma Sheet of the Magnetotail during Bursty Bulk Flows

MMS four-spacecraft observations with high temporal and spatial resolution made it possible to study the characteristics of intense superthin current sheets (SCSs) with a current density J > 30 nA/m2, formed in bursty bulk flows (BBFs), propagating in the Plasma Sheet (PS) of the magnetotail from the remote X line. Statistical analysis of >1000 SCSs observations showed that, in the majority of cases, the current in the SCSs is parallel to the ambient magnetic field and is carried by field-aligned accelerated electron beams. The half-thickness of the SCSs is several electron gyroradii, and in such thin layers the electric current is carried by demagnetized electrons. Bursts of strong nonideal electric fields E' > 10 mV/m are often observed at the edges and/or inside the SCSs. The generation of such fields brings about energy conversion in the SCSs of hundreds of pW/m3, and in some cases up to several nW/m3, which is comparable to the energy conversion in the electron diffusion region of magnetic reconnection. The strongest energy release is observed in the SCSs formed in the fastest BBFs and under strong variations of the magnetic field in the tail lobes.