Scheme of electron heating by the shock potential in the shock foot. Red ellipses indicate dense Weibel filaments. The motions of electrons are designated by red arrows. The blue arrow is the shock potential, E_x, in the shock foot. ﹩{\lambda }_{\mathrm{si}}﹩ represents the Weibel instability wavelength and L is a measure of a magnetic field line widening because of B_x amplification.