Open AccessThinning and stretching of the plasma sheet
Author(s) -
Petrukovich A. A.,
Baumjohann W.,
Nakamura R.,
Runov A.,
Balogh A.,
Rème H.
Publication year - 2007
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 - 10.1029/2007ja012349
Subject(s) - substorm , plasma sheet , current sheet , plasma , physics , current (fluid) , current density , cluster (spacecraft) , adiabatic process , magnetic field , atomic physics , magnetosphere , magnetohydrodynamics , thermodynamics , nuclear physics , quantum mechanics , computer science , programming language
With Cluster observations in the magnetotail we study dynamics of plasma sheet thinning and stretching during 39 intervals associated with substorm growth phases. The cross‐tail current density and normal magnetic field generally scale as B n ∼ T p N p 1/2 / J 0 , but with frequent transient variations. Typical pre‐onset values are B z ∼ 1–2 nT, J 0 ∼ 4–8 nA/m 2 , thickness (Harris estimate) >3000 km. A current density increase in each particular event is not accompanied with a corresponding number density increase. About 30% of the events are characterized by a large (>5 nT) field component parallel to the current (in most of cases equal to B y ), implying adiabatic particle dynamics even with small B z . Most local onsets, associated with the ends of thin sheet intervals, were accompanied with tailward plasma flows. In some cases embedded current sheet structure was detected and, therefore, estimation of thickness requires caution.