Electron penetration heating in turbulent magnetic loops driven by nonrelativistic laser-plasma interaction

Using particle-in-cell simulations to study nonrelativistic laser pulse propagation in an under-critical plasma, we identify a novel mechanism that occurs during the growth of turbulent magnetic loops: electron penetration heating. The loops have an electromagnetic left-hand chirality distinct from that of well-known quasistatic magnetic islands. The fast electrons penetrate through the loops and thus are accelerated to unexpected relativistic energies due to the symmetry breaking induced by the coupling between the loop field and the nonrelativistic electromagnetic wave. The identified features of penetration heating and magnetic loops might provide an alternative perspective for understanding superponderomotive electron heating in under-critical plasmas irradiated by nonrelativistic laser pulses. This is a potential explanation for anomalous hot electron generation in scenarios of laser-driven inertial confinement fusion.