  Magnetic field are transported and tangled by turbulence, even as they lose
identity due to nonideal or resistive effects. On balance field lines undergo
stretch-twist-fold processes. The curvature field, a scalar that measures the
tangling of the magnetic field lines, is studied in detail here, in the context
of magnetohydrodynamic turbulence. A central finding is that the magnitudes of
the curvature and the magnetic field are anti-correlated. High curvature
co-locates with low magnetic field, which gives rise to power-law tails of the
probability density function of the curvature field. The curvature drift term
that converts magnetic energy into flow and thermal energy, largely depends on
the curvature field behavior, a relationship that helps to explain particle
acceleration due to curvature drift. This adds as well to evidence that
turbulent effects most likely play an essential role in particle energization
since turbulence drives stronger tangled field configurations, and therefore
curvature.
