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Title: Evolution of Kelvin-Helmholtz instability at Venus in the presence of the parallel magnetic field

Two-dimensional MHD simulations were performed to study the evolution of the Kelvin-Helmholtz (KH) instability at the Venusian ionopause in response to the strong flow shear in presence of the in-plane magnetic field parallel to the flow direction. The physical behavior of the KH instability as well as the triggering and occurrence conditions for highly rolled-up vortices are characterized through several physical parameters, including Alfvén Mach number on the upper side of the layer, the density ratio, and the ratio of parallel magnetic fields between two sides of the layer. Using these parameters, the simulations show that both the high density ratio and the parallel magnetic field component across the boundary layer play a role of stabilizing the instability. In the high density ratio case, the amount of total magnetic energy in the final quasi-steady status is much more than that in the initial status, which is clearly different from the case with low density ratio. We particularly investigate the nonlinear development of the case that has a high density ratio and uniform magnetic field. Before the instability saturation, a single magnetic island is formed and evolves into two quasi-steady islands in the non-linear phase. A quasi-steady pattern eventually forms andmore » is embedded within a uniform magnetic field and a broadened boundary layer. The estimation of loss rates of ions from Venus indicates that the stabilizing effect of the parallel magnetic field component on the KH instability becomes strong in the case of high density ratio.« less
Authors:
 [1] ;  [2] ; ;  [1] ;  [3] ;  [4]
  1. Space Science Institute, School of Astronautics, Beihang University, Beijing 100191 (China)
  2. (China)
  3. Space Research Institute, Austrian Academy of Sciences, Graz A-8042 (Austria)
  4. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029 (China)
Publication Date:
OSTI Identifier:
22490939
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 6; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALFVEN WAVES; BOUNDARY LAYERS; DENSITY; HELMHOLTZ INSTABILITY; IONS; MACH NUMBER; MAGNETIC FIELDS; MAGNETIC ISLANDS; MAGNETOHYDRODYNAMICS; NONLINEAR PROBLEMS; SHEAR; SIMULATION; TWO-DIMENSIONAL CALCULATIONS; VENUS PLANET; VORTICES