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

Spontaneously generated magnetic fields B can be generated by nonuniform laser irradiation causing sources such as ▽Tₑ×▽nₑ/nₑe. By considering convective losses and dissipation including the triggering of lower hybrid drift turbulence a universal diagram of saturated B versus L_⊥, the characteristic transverse scale length for the nonuniformity, is found. For L_⊥ less than the ion collisionless skin depth c/ωₚᵢ the saturated B scales as L_⊥^α α≤1. At higher L_⊥ values B scales as L_⊥^-1 because convective losses dominate. For resistive plasmas (e.g., high Z, low temperature) B will be limited to (μ₀kTₑ/eη)(L_⊥/L_) where L_ is nₑ/▽nₑ.