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Jet front‐driven mirror modes and shocklets in the near‐Earth flow‐braking region
Author(s) -
Zieger Bertalan,
Retinò Alessandro,
Nakamura Rumi,
Baumjohann Wolfgang,
Vaivads Andris,
Khotyaintsev Yuri
Publication year - 2011
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 - 10.1029/2011gl049746
Subject(s) - front (military) , jet (fluid) , physics , flow (mathematics) , mechanics , spacecraft , geology , cluster (spacecraft) , aerospace engineering , scale (ratio) , geophysics , meteorology , computer science , astronomy , engineering , quantum mechanics , programming language
We investigate the small‐scale structure of jet fronts through a case study of multi‐spacecraft Cluster observations in the near‐Earth flow‐braking region at ∼−10 R E . We find that the interaction between the earthward moving fast plasma jet and the high‐ β ambient plasma in the plasma sheet results in magnetic pileup and compression ahead of the jet and rarefaction trailing the jet. It is shown that mirror‐mode structures of ion gyroradius scale develop within the pileup region due to the observed ion temperature anisotropy ( T i ⊥ > T i ∥ ). We suggest that the growth of these mirror modes is driven by the perpendicular total pressure perturbation (Δ p ⊥ ) generated by the braking jet. When Δ p ⊥ becomes too large, the mirror‐mode structure cannot maintain pressure balance any longer, and consequently a shocklet is formed in the pileup region ahead of the jet front. We present the first evidence for such a kinetic shocklet in the flow‐braking region.