Probing the impact of stochastic plasma in solar flare MHD turbulence on thermal x-ray background: A theoretical study

Magnetohydrodynamic (MHD) turbulence during the impulsive phase of solar flares drives stochastic and non-stochastic plasma motions, influencing background x-ray emissions. This study investigates the impact of stochastic plasma, modeled with a Gaussian temperature distribution from 10 to 40 MK, representative of X-class solar flares using RHESSI observations, on theoretically assumed background x rays in the 1–10 keV range. Using statistical models grounded in the hydrodynamic approximation of turbulence, particularly second-order structure functions, we estimate optical turbulence intensity and coherence properties of the x rays. Monte Carlo simulations over multiple spatial scales yield a refractive index structure constant in the range (1–47)×10−32 m−2/3. The wave structure function indicates fluctuating x-ray wave-fronts with separations between ∼7 and 300 m. The mutual coherence function shows a mean value ∼0.13 under turbulent conditions. A consistent ∼2% reduction in turbulence intensity is observed with increasing turbulence and coherence length scales. These findings demonstrate the x-ray intensity fluctuations due to thermal fluctuations in turbulent solar flare plasmas and offer new insight into the role of MHD turbulence in shaping background x-ray emission.