TEARING MODES GROWTH RATE AMPLIFICATION DUE TO FINITE CURRENT RELAXATION

Abstract

In this work, we explore the influence of perturbative wavelengths, shorter than those usually considered, on the growth rate γ of the tearing modes. Thus, we adopt an extended form of Ohm’s law, which includes a finite relaxation time for the current density, due to inertial effects of charged species. In the long wavelength limit, we observe the standard γ of the tearing modes. However, in the short wavelength limit, we show that γ does not depend on the fluid resistivity any longer. Actually, we find out that γ now scales with the electron number density n_e as γ ~ n_e^−3/2. Therefore, through a suitable combination of both limiting results, we show that the standard γ can be substantially amplificated, even by moderate shortenings of perturbative wavelengths. Further developments of our theory may contribute to the explanation of the fast magnetic reconnection of field lines, as observed in astrophysical plasmas.