Electron dynamics in a subproton-gyroscale magnetic hole

Daniel J. Gershman , John C. Dorelli , Adolfo F. Viñas , Levon A. Avanov , Ulrik Gliese , Alexander C. Barrie , Victoria Coffey , Michael Chandler , Charles Dickson , Elizabeth A. Macdonald , Chad Salo , Matthew Holland , Yoshifumi Saito , Jean-Andre Sauvaud (1) , Benoit Lavraud (1) , William R. Paterson , Roy Torbert , Li-Jen Chen , Katherine Goodrich , Christopher T. Russell , Robert J. Strangeway , Barbara L. Giles , Craig J. Pollock , Thomas E. Moore , James L. Burch

1 IRAP - Institut de recherche en astrophysique et planétologie

Magnetic holes are ubiquitous in space plasmas, occurring in the solar wind, downstream of planetary bow shocks, and inside the magnetosphere. Recently, kinetic-scale magnetic holes have been observed near Earth's central plasma sheet. The Fast Plasma Investigation on NASA's Magnetospheric Multiscale (MMS) mission enables measurement of both ions and electrons with 2 orders of magnitude increased temporal resolution over previous magnetospheric instruments. Here we present data from MMS taken in Earth's nightside plasma sheet and use high-resolution particle and magnetometer data to characterize the structure of a subproton-scale magnetic hole. Electrons with gyroradii above the thermal gyroradius but below the current layer thickness carry a current sufficient to account for a ~10-20% depression in magnetic field magnitude. These observations suggest that the size and magnetic depth of kinetic-scale magnetic holes is strongly dependent on the background plasma conditions.

Mots clés: magnetic hole; electron dynamics; kinetic plasma; MMS; FPI

Domaines: Planète et Univers [physics]

Daniel J. Gershman, John C. Dorelli, Adolfo F. Viñas, Levon A. Avanov, Ulrik Gliese, et al.. Electron dynamics in a subproton-gyroscale magnetic hole. Geophysical Research Letters, 2016, 43, pp.4112-4118. ⟨10.1002/2016GL068545⟩. ⟨insu-03670244⟩