Open AccessObservations of an active thin current sheet
Author(s) -
Runov A.,
Baumjohann W.,
Nakamura R.,
Sergeev V. A.,
Amm O.,
Frey H.,
Alexeev I.,
Fazakerley A. N.,
Owen C. J.,
Lucek E.,
André M.,
Vaivads A.,
Dandouras I.,
Klecker B.
Publication year - 2008
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2007ja012685
Subject(s) - substorm , current sheet , plasma sheet , physics , current (fluid) , magnetometer , geophysics , magnetic reconnection , current density , magnetosphere , astrophysics , plasma , magnetic field , magnetohydrodynamics , quantum mechanics , thermodynamics
We analyze observations of magnetotail current sheet dynamics during a substorm between 2330 and 2400 UT on 28 August 2005 when Cluster was in the plasma sheet at [−17.2, −4.49, 0.03] R E (GSM) with the foot points near the IMAGE ground‐based network. Observations from the Cluster spacecraft, ground‐based magnetometers, and the IMAGE satellite showed that the substorm started in a localized region near midnight, expanding azimuthally. A thin current sheet with a thickness of less than 900 km and current density of about 30 nA/m 2 was observed during 5 min around the substorm onset. The thinning of the current sheet was accompanied by tailward plasma flow at a velocity of −700 km/s and subsequent reversal to earthward flow at V x ≈ 500 km/s coinciding with a B z turning from −5 to +10 nT. The analysis of magnetic and electric fields behavior and particle distributions reveals signatures of impulsive (with ∼1 min timescale) activations of the thin current sheet. These observations were interpreted in the framework of transient reconnection, although the data analysis reveals serious disagreements with the classical 2.5‐D X line model.