A plasma flow induces mixing of magnetic flux, and the length scale cascades toward a small scale, resulting in amplification of the magnetic field. If the enhanced Lorentz force comes to dominate the dynamics, its backreaction should be taken into account. The magnetic force-free condition, which is amenable to slow motion of a strongly magnetized plasma, imposes a lower bound for the length scale. This bound avoids scale reduction down to the resistive regime, and extends the lifetime of the amplified magnetic field.

• Received 15 April 1996

DOI:https://doi.org/10.1103/PhysRevLett.77.2722