MAGNETOHYDRODYNAMIC INSTABILITIES IN DEVELOPED SMALL-SCALE TURBULENCE

Modification of the magnetic force by a developed small-scale magnetoh ydrodynamic (MHD) turbulence can result in the sip reversal of the eff ective magnetic pressure. It is due to negative contribution of the MH D turbulence, to the large-scale magnetic force. It can significantly lower the elasticity of the large-scale magnetic field [ Sov. Phys. JE TP 70, 878 (1990)]. This effect excites instabilities of the large-sca le magnetic field due to the energy transfer from the turbulent pulsat ions to the latter. The nonturbulent stability criteria are modified d ue to the effective negative magnetic pressure. These instabilities ma y provide a mechanism of the large-scale magnetic ropes formation in t he solar convective zone and spiral galaxies. In addition, the instabi lities can excite the short-period solar oscillations.