Physical picture for the laser hosing instability in a plasma

The hosing of a light beam centroid is caused by upward or downward tilting of the local wave fronts due to the transverse phase velocity difference across the wave fronts. The phase velocity gradient is caused by the plasma density perturbation, which in turn is driven by the ponderomotive force of the hosing light beam. The hosing equations in both long- and short-wavelength regimes can be heuristically derived from this physical picture.