Open AccessShear flow instabilities in the Earth's magnetotail
Author(s) -
R. V. Reddy,
G. S. Lakhina
Publication year - 1996
Publication title -
annales geophysicae
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.522
H-Index - 93
eISSN - 1432-0576
pISSN - 0992-7689
DOI - 10.1007/s00585-996-0786-z
Subject(s) - plasma sheet , physics , plasma , boundary layer , instability , magnetohydrodynamics , mach number , oscillation (cell signaling) , excited state , dispersion relation , wavelength , atomic physics , substorm , mechanics , geophysics , magnetosphere , optics , chemistry , biochemistry , quantum mechanics
Shear flow instability is studied in the\udEarth's magnetotail by treating plasma as compressible. A dispersion relation is\udderived from the linearized MHD equations using the oscillating boundary\udconditions at the inner central plasma sheet/outer central plasma sheet (OCPS)\udinterface and OCPS/plasma-sheet boundary layer (PSBL) interface, whereas the\udsurface-mode boundary condition is used at the PSBL/lobe interface. The growth\udrates and the real frequencies are obtained numerically for near-Earth (∣X∣~10–15\udRE) and far-Earth (∣X∣~100 RE)\udmagnetotail parameters. The periods and wavelengths of excited modes depend\udsensitively on the value of plasma-sheet half thickness, L, which is\udtaken as L=5 RE for quiet time and L=1 RE\udfor disturbed time. The plasma-sheet region is found to be stable for constant\udplasma flows unless MA3>1.25, where MA3\udis the Alfvén Mach number in PSBL. For near-Earth magnetotail, the excited\udoscillations have periods of 2–20 min (quiet time) and 0.5–4 min (disturbed\udtime) with typical transverse wavelengths of 2–30 RE and\ud0.5–6.5 RE, respectively; whereas for distant magnetotail, the\udanalysis predicts the oscillation periods of ~8–80 min for quiet periods and\ud2–16 min for disturbed periods