Seminar: Ion/Electron Diffusion Regions at a Flapping/Twisted Tail Current Sheet

Wednesday, April 14, 2021 - 3:00pm to 4:00pm

Speaker: Charles Farrugia, UNH

Abstract: In this talk, we analyze data returned by the Magnetospheric Multiscale mission (MMS) constellation during a rapid (~1.5 s) traversal of a flapping and reconnecting current sheet (CS) in the near-Earth magnetotail (X ~ -20 RE) on June 17, 2017. The CS was highly tilted, with its normal pointing strongly duskward. Its extreme thinness was confirmed by a curvature analysis of the magnetic field lines. The event was associated with a guide field of ~8% of the reconnecting components. From the pitch angle distribution of low-energy electrons we infer a crossing earthward of the X-line.   While traveling practically normal to the CS, MMS encountered an ion diffusion region (IDR) in which was embedded an electron diffusion region (EDR). IDR signatures included breaking of the ion frozen-in condition in the presence of Hall magnetic and electric fields. EDR signatures included a strong out-of-plane current associated with a super-Alfvenic electron jet, positive energy transfer, and a temperature anisotropy (with Te[par] > Te[perp]) which disappeared at the field reversal.  Derived scale sizes normal to the CS are: ~6.9 de (EDR) and ~0.4 di  (IDR) (40 and 100 km, respectively).  We estimate the average dimensionless reconnection rate as 0.077 +/- 0.050. The observations and inferences are  supported by  PIC numerical simulations. We find very good agreement in the reconnection rates. We also discuss the effects of asymmetries in the density, temperature and magnetic field strength on the Hall fields and length of the outflow jets. The event is associated with a substorm onset which began 7 min after the MMS observations. 

The presentation is based on a paper by Farrugia, Rogers, Torbert, Genestreti, Nakamura et al.,  recently published in J. Geophys. Res.

 This online seminar will take place on Zoom and will require a password to join. If you wish to watch the seminar and have not received a password via email, please contact Robbin McPherson at


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