A Hall dynamo effect driven by two-fluid tearing instability

A quasi-linear prediction of the two-fluid dynamo effect is analyzed with the use of tearing eigen-functions obtained for force-free equilibrium. In the range of parameters of practical interest, the basic shear Alven mode is decoupled from fast compressional Alfven and slow magneto-acoustic modes. Kinetic Alven modification of the shear Alfven wave drives an instability with a growth rate proportional todelta(1/3)rho(s)(2/3), where delta theelectron skin depth and rho(s) is the ion-sound gyroradius. A net dynamo effect parallel to the magnetic field is calculated at rho(s) much greater than delta for large values of the stability factor Delta'rho(s)(1/3) delta(2/3) much greater than 1. The dynamo effect caused by the j X B Hall term dominates the contribution from the v X B term (the alpha effect) by a factor proportional to(rho(s)/delta)(2) in the narrow electron layer, while in the broader ion layer these contributions are comparable. The results are compared with the case of a strong guiding field where rho(s) much less than delta and the tearing instability is described by resistive MHD. (C) 2003 MAIK "Nauka/Interperiodica".