http://arxiv.org/abs/2212.07487
A driven evolution of a magnetic field has three aspects: field line topology, magnetic energy, and magnetic helicity. An ideal evolution with minimal energy input can produce magnetic field line chaos, which makes the preservation of field-line topology exponentially sensitive to non-ideal effects on an evolution timescale, but has no direct effect on energy or helicity dissipation. Resistive dissipation of the power input requires highly localized current densities $j\approx vB/\eta$, where $v$ is the velocity given by the evolution drive and $\eta$ is the plasma resistivity. Dissipation of the magnetic helicity input cannot be balanced when the magnetic Reynolds number is large compared to unity. Current densities $j\approx vB/\eta$ are consistent with those required to produce the solar corona with the observed height of the transition region by the Dreicer electron runaway effect.
A. Boozer
Fri, 16 Dec 22
34/72
Comments: N/A