Short-pulse laser absorption via J×B heating in ultrahigh intensity laser plasma interaction

An analytical fluid model for J×B heating during the normal incidence by a short ultraintense linearly polarized laser on a solid-density plasma is proposed. The steepening of an originally smooth electron density profile as the electrons are pushed inward by the laser is included self-consistently. It is shown that the J×B heating includes two distinct coupling processes depending on the initial laser and plasma conditions: for a moderate intensity (a⩽1), the ponderomotive force of the laser light can drive a large plasma wave at the point ne=4γ0nc resonantly. When this plasma wave is damped, the energy is transferred to the plasma. At higher intensity, the electron density is steepened to a high level by the time-independent ponderomotive force, ne>4γ0nc, so that no 2ω resonance will occur, but the longitudinal component of the oscillating ponderomotive field can lead to an absorption mechanism similar to “vacuum heating.”