Heat Transport Effects in Magnetised Laser-Plasmas with Large Temperature Gradients

Key to accurately predicting heat-flow in many laser-plasma systems is understanding the effect of non-local transport, where the heat-flow at a given point in the plasma is no longer determined solely by local conditions. For laser-plasma systems non-local transport is often most significant at the heat-front, where the mean-free-path of electrons can be long compared to the temperature length scale. Incorporating non-local effects on heat-flow in predictive models is challenging though, often requiring extended fluid or kinetic modelling. Moreover, magnetic fields in plasmas modify and restrict heat transport. Here we describe how a magnetic field can limit the emergence of non-local transport effects. Transitioning from the weakly magnetised regime where the gyrofrequency is smaller than the collision frequency and the Hall parameter is small, to a strongly magnetised case with a Hall parameter exceeding unity, the magnetic field acts to reduce the distance travelled by heat carriers. Here, the decreasing collisionality counter-intuitively leads to more local transport. This demonstrates that fluid models of magnetised plasmas can be valid even in a regime where the thermal mean-free-path of the electrons exceeds the temperature length scale.