KELVIN-HELMHOLTZ INSTABILITY IN SUPERCONVECTION CELLS AS A POSSIBLE MECHANISM FOR SOLAR SPICULE FORMATION

It is proposed that the formation of solar spicules is caused by colle ctive plasma processes-MHD Kelvin-Helmholtz instabilities at the bound ary between the chromosphere and a surface layer of photospheric mater ial quasi-radially spreading outward from the center of a supergranula tion cell. The dispersive properties of perturbations at a tangential discontinuity of the velocity and magnetic field in a gravitational fi eld perpendicular to the discontinuity surface are described using an equation derived for the case of an ideal compressible gas. Numerical solution of this dispersion equation indicates that the parameters of structures created during the initial stage of the development of inst abilities are in agreement with observations. Based on a qualitative a nalysis with account for magnetic field reconnection effects, it is co ncluded that the nonlinear stage of the instabilities leads to the for mation of objects similar to real spicules and to the observed inhomog eneity and nonstationarity of the lower chromosphere.