Saturation Mechanisms for the Generated Magnetic Field in Nonuniform Laser-Matter Irradiation

Abstract

Spontaneously generated magnetic fields {bold {ital B}} can be generated by nonuniform laser irradiation causing sources such as {triangledown}T{sub e}{times}{triangledown}n{sub e}/n{sub e}e. By considering convective losses and dissipation including the triggering of lower hybrid drift turbulence a universal diagram of saturated {bold {ital B}} versus L{sub {perpendicular}}, the characteristic transverse scale length for the nonuniformity, is found. For L{sub {perpendicular}} less than the ion collisionless skin depth c/{omega}{sub pi} the saturated {bold {ital B}} scales as L{sup {alpha}}{sub {perpendicular}} {alpha}{le}1. At higher L{sub {perpendicular}} values {bold {ital B}} scales as L{sup -1}{sub {perpendicular}} because convective losses dominate. For resistive plasmas (e.g., high {bold {ital Z}}, low temperature) {bold {ital B}} will be limited to ({mu}{sub 0}kT{sub e}/e{eta})(L{sub {perpendicular}}/L{sub {parallel}}) where L{sub {parallel}} is n{sub e}/{triangledown}n{sub e}. {copyright} {ital 1997} {ital The American Physical Society}