  High-amplitude, chaotic/turbulent electromagnetic fluctuations are ubiquitous
in high-energy-density laboratory and astrophysical plasmas, where they can be
excited by various kinetic-streaming and/or anisotropy-driven instabilities,
such as the Weibel instability. These fields typically exist on "sub-Larmor
scales" -- scales smaller than the electron Larmor radius. Electrons moving
through such magnetic fields undergo small-angle stochastic deflections of
their pitch-angles, thus establishing diffusive transport on long time-scales.
We show that this behavior, under certain conditions, is equivalent to Coulomb
collisions in collisional plasmas. The magnetic pitch-angle diffusion
coefficient, which acts as an effective "collision" frequency, may be
substantial in these, otherwise, collisionless environments. We show that this
effect, colloquially referred to as the plasma "quasicollisionality", may
radically alter the expected radiative transport properties of candidate
plasmas. We argue that the modified magneto-optic effects in these plasmas
provide an attractive, novel radiative diagnostic tool for the exploration and
characterization of small-scale magnetic turbulence, as well as affect inertial
confinement fusion and other laser-plasma experiments.
