A possible mechanism of energy dissipation in the front of a shock wave driven ahead of a coronal mass ejection

Mark 4 and LASCO C2, C3 coronagraph data analysis shows that, up to the distance $R\sim$ 5 R$_\odot$ from the center of the Sun, the thickness of a CME-generated shock front may be of order of the proton mean free path. This means that the energy dissipation mechanism in a shock front at these distances is collisional.