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The dependence of magnetic reconnection on plasma β and magnetic shear: Evidence from magnetopause observations
Author(s) -
Phan T. D.,
Paschmann G.,
Gosling J. T.,
Oieroset M,
Fujimoto M.,
Drake J. F.,
Angelopoulos V.
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2012gl054528
Subject(s) - magnetic reconnection , magnetopause , physics , current sheet , geophysics , plasma , shear (geology) , astrophysics , space physics , plasma sheet , computational physics , magnetosphere , magnetohydrodynamics , geology , quantum mechanics , petrology
We have performed a statistical study of THEMIS spacecraft crossings of the asymmetric dayside magnetopause to test the prediction that the diamagnetic drift of the X‐line due to a plasma pressure gradient across the magnetopause can suppress magnetic reconnection. The study includes crossings both when reconnection exhausts were present and when they were absent in the current sheet. When we restrict the survey to the subsolar region (10 < MLT < 14), we find that for low Δ β (the difference of plasma β on the two sides of the current sheet) the majority of reconnection events occurred over a large range of magnetic shears, whereas when Δ β was high reconnection events occurred only for high shears. Furthermore, nonreconnection events occurred primarily in the Δ β ‐shear regime in which reconnection is predicted to be suppressed, in good agreement with theory. The Δ β ‐shear condition should have general consequences for the occurrence of reconnection in space and laboratory plasmas.