Investigation of ponderomotive vs. thermal noise source on the onset of filamentation

Filamentation describes the formation of narrow, self-focused channels when an intense laser propagates through plasma. In this work, we investigate how ponderomotive effects, arising from both intrinsic plasma fluctuations and externally imposed speckle fields from overlapped laser beams, drive filamentation. Plasma fluctuations are modelled as a stochastic source with a known spectral density, while speckle fields are generated using a Random Phase Plate (RPP), producing a field with complex Gaussian distribution. Each mechanism is simulated independently using a paraxial nonlinear beam propagation model. We then combine them to examine their relative contributions and determine the dominant driver of filamentation. A spectral analysis in Fourier space is used to compare growth rates and intensity distributions.