Finite gyroradius effects in the electron outflow of asymmetric magnetic reconnection

C. Norgren , D. B. Graham , Yu. V. Khotyaintsev , M. André , A. Vaivads , L. -J. Chen , P. -A. Lindqvist , G. T. Marklund , R. E. Ergun , W. Magnes , R. J. Strangeway , C. T. Russell , R. B. Torbert , W. R. Paterson , D. J. Gershman , J. C. Dorelli , L. A. Avanov , B. Lavraud (1) , Y. Saito , B. L. Giles , C. J. Pollock , J. L. Burch

1 IRAP - Institut de recherche en astrophysique et planétologie

We present observations of asymmetric magnetic reconnection showing evidence of electron demagnetization in the electron outflow. The observations were made at the magnetopause by the four Magnetospheric Multiscale (MMS) spacecraft, separated by ∼15 km. The reconnecting current sheet has negligible guide field, and all four spacecraft likely pass close to the electron diffusion region just south of the X line. In the electron outflow near the X line, all four spacecraft observe highly structured electron distributions in a region comparable to a few electron gyroradii. The distributions consist of a core with T_∥>T_⊥ and a nongyrotropic crescent perpendicular to the magnetic field. The crescents are associated with finite gyroradius effects of partly demagnetized electrons. These observations clearly demonstrate the manifestation of finite gyroradius effects in an electron-scale reconnection current sheet.

Keywords: magnetic reconnection; electron demagnetization; finite gyroradius effects; electron diffusion region

Domains: Sciences of the Universe [physics]; Earth Sciences

C. Norgren, D. B. Graham, Yu. V. Khotyaintsev, M. André, A. Vaivads, et al.. Finite gyroradius effects in the electron outflow of asymmetric magnetic reconnection. Geophysical Research Letters, 2016, 43, pp.6724-6733. ⟨10.1002/2016GL069205⟩. ⟨insu-03669466⟩