Collisional shear instability in the equatorial F region ionosphere

[1] A collisional shear instability in a magnetized plasma is described and evaluated. The instability is related to electrostatic Kelvin Helmholtz but operates in inhomogeneous plasmas in the collisional regime. Boundary value analysis predicts that the linear growth rate for the instability could be comparable to that of the collisional interchange instability in the equatorial F region ionosphere under ideal conditions. An initial value simulation of a nonlinear model of the instability run under realistic conditions produces growing waves with a relatively long growth time (50 min) and with an initial wavelength of about 30 km. The simulation results are consistent with recent radar observations showing large-scale plasma waves in the bottomside equatorial ionosphere at sunset prior to the onset of spread F conditions. The role of shear instability in preconditioning the F region for interchange instabilities to occur after sunset is discussed.

[1]  C. Seyler,et al.  Collisional and inertial dynamics of the ionospheric interchange instability , 1989 .

[2]  M. Kelley,et al.  On the combined effects of vertical shear and zonal electric field patterns on nonlinear equatorial spread F evolution , 1998 .

[3]  G. Haerendel,et al.  The role of the equatorial electrojet in the evening ionosphere , 1992 .

[4]  S. Chandrasekhar.  Hydrodynamic and Hydromagnetic Stability , 1961 .

[5]  D. T. Farley,et al.  Interferometer studies of equatorial F region irregularities and drifts , 1981 .

[6]  David L. Hysell,et al.  An overview and synthesis of plasma irregularities in equatorial spread F , 2000 .

[7]  Lou‐Chuang Lee,et al.  A quasi‐local theory of the E × B instability in the ionosphere , 1986 .

[8]  D. Hysell,et al.  JULIA radar studies of equatorial spread F , 1998 .

[9]  Ronald F. Woodman,et al.  Radar observations of F region equatorial irregularities , 1976 .

[10]  R. Sudan,et al.  A nonlocal linear theory of the gradient drift instability in the equatorial electrojet , 1989 .

[11]  D. Hysell,et al.  Electrostatic plasma turbulence in the topside equatorial F region ionosphere , 2002 .

[12]  N. D’angelo,et al.  Kelvin—Helmholtz Instability in a Fully Ionized Plasma in a Magnetic Field , 1965 .

[13]  S. Zalesak,et al.  Nonlinear evolution of the Kelvin-Helmholtz instability in the high-latitude ionosphere. Interim report , 1987 .

[14]  J. Huba,et al.  Influence of velocity shear on the Rayleigh-Taylor instability. Memorandum report , 1981 .

[15]  M. Larsen,et al.  Gravity wave initiation of equatorial spread F: A case study , 1981 .

[16]  H. U. Rahman,et al.  The Rayleigh–Taylor Mode with Sheared Plasma Flows , 1998 .

[17]  Y. C. Lee,et al.  Transverse Kelvin-Helmholtz instability with parallel electron dynamics and Coulomb collisions. Interim report , 1987 .

[18]  S. Basu,et al.  F region electron density irregularity spectra near auroral acceleration and shear regions , 1984 .

[19]  Adil Hassam,et al.  Nonlinear stabilization of the Rayleigh–Taylor instability by external velocity shear , 1992 .

[20]  C. Rino,et al.  Evidence of a velocity shear in bulk plasma motion associated with the post‐sunset rise of the equatorial F‐layer , 1981 .

[21]  Lou‐Chuang Lee,et al.  Short wavelength stabilization of the gradient drift instability due to velocity shear , 1983 .

[22]  Erhan Kudeki,et al.  Postsunset vortex in equatorial F‐region plasma drifts and implications for bottomside spread‐F , 1999 .

[23]  G. Lakhina,et al.  Collisional Rayleigh-Taylor instability and shear-flow in equatorial Spread-F plasma , 2003 .

[24]  J. Huba,et al.  Rayleigh‐Taylor instability in the presence of a stratified shear layer , 1984 .

[25]  G. Haerendel,et al.  Theory for modeling the equatorial evening ionosphere and the origin of the shear in the horizontal plasma flow , 1992 .

[26]  Y. C. Lee,et al.  The stability of a stratified shear layer , 1986 .

[27]  J. Willig,et al.  Experimental study of the collisional parallel velocity shear instability , 1997 .

[28]  J. Chau,et al.  Bottom-type scattering layers and equatorial spread F , 2004 .

[29]  Lloyd N. Trefethen,et al.  Large‐amplitude transient growth in the linear evolution of equatorial spread F with a sheared zonal flow , 1999 .

[30]  B. Coppi,et al.  Fluctuations associated with sheared velocity regions near auroral arcs , 1988 .

[31]  B. Coppi,et al.  Velocity shear and fluctuations in the auroral regions of the ionosphere , 1989 .