Transient, small-scale field-aligned currents in the plasma sheet boundary layer during storm time substorms

R Nakamura; V A Sergeev; W Baumjohann; F Plaschke; W Magnes; D Fischer; A Varsani; D Schmid; T K M Nakamura; C T Russell; R J Strangeway; H K Leinweber; G Le; K R Bromund; C J Pollock; B L Giles; J C Dorelli; D J Gershman; W Paterson; L A Avanov; S A Fuselier; K Genestreti; J L Burch; R B Torbert; M Chutter; M R Argall; B J Anderson; P-A Lindqvist; G T Marklund; Y V Khotyaintsev; B H Mauk; I J Cohen; D N Baker; A N Jaynes; R E Ergun; H J Singer; J A Slavin; E L Kepko; T E Moore; B Lavraud; V Coffey; Y Saito

doi:10.1002/2016GL068768

Transient, small-scale field-aligned currents in the plasma sheet boundary layer during storm time substorms

Geophys Res Lett. 2016 May 28;43(10):4841-4849. doi: 10.1002/2016GL068768. Epub 2016 May 30.

Authors

R Nakamura¹, V A Sergeev², W Baumjohann¹, F Plaschke¹, W Magnes¹, D Fischer¹, A Varsani¹, D Schmid¹, T K M Nakamura¹, C T Russell³, R J Strangeway³, H K Leinweber³, G Le⁴, K R Bromund⁴, C J Pollock⁵, B L Giles⁴, J C Dorelli⁴, D J Gershman⁴, W Paterson⁴, L A Avanov⁴, S A Fuselier⁶, K Genestreti⁷, J L Burch⁷, R B Torbert⁸, M Chutter⁹, M R Argall⁹, B J Anderson¹⁰, P-A Lindqvist¹¹, G T Marklund¹¹, Y V Khotyaintsev¹², B H Mauk¹⁰, I J Cohen¹⁰, D N Baker¹³, A N Jaynes¹³, R E Ergun¹³, H J Singer¹⁴, J A Slavin¹⁵, E L Kepko⁴, T E Moore⁴, B Lavraud¹⁶, V Coffey¹⁷, Y Saito¹⁸

Affiliations

¹ Space Research Institute Austrian Academy of Sciences Graz Austria.
² Earth Physics Department St. Petersburg State University St. Petersburg Russia.
³ Institute of Geophysics and Planetary Physics and Earth and Space Sciences Department University of California Los Angeles California USA.
⁴ Goddard Space Flight Center NASA College Park Maryland USA.
⁵ Goddard Space Flight Center NASA College Park Maryland USA; Denali Scientific Healy Alaska USA.
⁶ Southwest Research InstituteSan AntonioTexasUSA; University of Texas at San AntonioSan AntonioTXUSA.
⁷ Southwest Research Institute San Antonio Texas USA.
⁸ Southwest Research Institute San Antonio Texas USA; Physics Department University of New Hampshire Durham New Hampshire USA.
⁹ Physics Department University of New Hampshire Durham New Hampshire USA.
¹⁰ Applied Physics Laboratory The Johns Hopkins University Laurel Maryland USA.
¹¹ Space and Plasma Physics Royal Institute of Technology Stockholm Sweden.
¹² Swedish Institute of Space Physics Uppsala Sweden.
¹³ University of Colorado Boulder Colorado USA.
¹⁴ NOAA Space Weather Prediction Center Boulder Colorado USA.
¹⁵ Department of Climate and Space Sciences and Engineering University of Michigan Ann Arbor Michigan USA.
¹⁶ Centre National de la Recherche Scientifique Toulouse France.
¹⁷ NASA Marshall Space Flight Center Huntsville Alabama USA.
¹⁸ JAXA Institute for Space and Astronautical Science Sagamihara Japan.

Abstract

We report on field-aligned current observations by the four Magnetospheric Multiscale (MMS) spacecraft near the plasma sheet boundary layer (PSBL) during two major substorms on 23 June 2015. Small-scale field-aligned currents were found embedded in fluctuating PSBL flux tubes near the separatrix region. We resolve, for the first time, short-lived earthward (downward) intense field-aligned current sheets with thicknesses of a few tens of kilometers, which are well below the ion scale, on flux tubes moving equatorward/earthward during outward plasma sheet expansion. They coincide with upward field-aligned electron beams with energies of a few hundred eV. These electrons are most likely due to acceleration associated with a reconnection jet or high-energy ion beam-produced disturbances. The observations highlight coupling of multiscale processes in PSBL as a consequence of magnetotail reconnection.

Keywords: MMS; PSBL; electron beam; field‐aligned currents.