Anomalous heating of plasma by laser irradiation

When an intense electric field oscillating near the electron plasma frequency is applied to a plasma, it excites parametric instabilities which drive up the ion density fluctuations. The presence of moderate ion density fluctuations leads to a strong enhancement of the high-frequency resistivity around the plasma frequency and hence to anomalous plasma heating. The enhancement of the resistivity, which can be physically attributed to a collective process involving the conversion of the electromagnetic wave energy into longitudinal plasma waves by a resonant mode coupling process involving the ion waves, can typically be many orders of magnitude. An account is given of evidence based on computer simulations, laboratory experiments with microwaves done elsewhere and in Princeton, and on experiments involving the radio wave propagation in ionosphere, which establishes the existence of such an effect beyond doubt. A semiquantitative theory to explain the laboratory and computer experiments is also presented.