KELVIN-HELMHOLTZ INSTABILITY IN PARTIALLY IONIZED COMPRESSIBLE PLASMAS

• Published in: The Astrophysical journal Vol. 749; no. 2; pp. 1 - 12
• Main Authors: SOLER, R, DIAZ, A. J, BALLESTER, J. L, GOOSSENS, M
• Format: Journal Article
• Language: English
• Published: Bristol IOP 20-04-2012
• Subjects: Astronomy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Collisions; COMPRESSIBILITY; Density; DISPERSION RELATIONS; Earth, ocean, space; Exact sciences and technology; HELMHOLTZ INSTABILITY; Kelvin-Helmholtz instability; MAGNETOHYDRODYNAMICS; PARAMETRIC ANALYSIS; PLASMA; Plasmas; Shear; Shear flow; SOLAR ATMOSPHERE; SOLAR PROMINENCES; SOLAR SYSTEM EVOLUTION; STAR EVOLUTION; SUN; Magnetohydrodynamics; Ion neutral collision; Kelvin Helmholtz instability; Growth rate; High density; Dispersion relations; Sun: corona; Shear flow; Solar prominences; Sun; instabilities; Partially ionized plasma; Sun: atmosphere; Sun: filaments, prominences; Filaments; Solar plasma; Collision frequency; Solar atmosphere; Flow velocity; magnetohydrodynamics (MHD); Velocity shear
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/749/2/163

The Kelvin-Helmholtz instability (KHI) has been observed in the solar atmosphere. Ion-neutral collisions may play a relevant role for the growth rate and evolution of the KHI in solar partially ionized plasmas such as in, e.g., solar prominences. Here, we investigate the linear phase of the KHI at an interface between two partially ionized magnetized plasmas in the presence of a shear flow. The effects of ion-neutral collisions and compressibility are included in the analysis. We obtain the dispersion relation of the linear modes and perform parametric studies of the unstable solutions. We find that, in the incompressible case, the KHI is present for any velocity shear regardless of the value of the collision frequency. In the compressible case, the domain of instability depends strongly on the plasma parameters, especially the collision frequency and the density contrast. For high collision frequencies and low density contrasts the KHI is present for super-Alfvenic velocity shear only. For high density contrasts the threshold velocity shear can be reduced to sub-Alfvenic values. For the particular case of turbulent plumes in prominences, we conclude that sub-Alfvenic flow velocities can trigger the KHI thanks to the ion-neutral coupling.