Authors: Peijin Zhang (Center for Solar-Terrestrial Research, New Jersey Institute of Technology, Newark, NJ 07102, USA), Bin Chen (Center for Solar-Terrestrial Research, New Jersey Institute of Technology, Newark, NJ 07102, USA), Gregory Fleishman (Center for Solar-Terrestrial Research, New Jersey Institute of Technology, Newark, NJ 07102, USA), Alexey Kuznetsov (Institute of Solar-Terrestrial Physics, Siberian Branch of the Russian Academy of Sciences, Irkutsk 664033, Russia), Cooper Downs (Predictive Science Inc., San Diego, CA 92121, USA), Surajit Mondal (National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune 411007, India), Sijie Yu (Center for Solar-Terrestrial Research, New Jersey Institute of Technology, Newark, NJ 07102, USA)

Incoherent radio emission at meter–decimeter wavelengths is a key diagnostic of thermal plasma in the quiet solar corona, but below about 1 GHz, refraction can strongly alter apparent source size and brightness. We develop a forward-modeling framework that combines refractive ray tracing through a global 3D coronal model with radiative transfer along each ray. The method tracks ray-tube expansion and incorporates geometric magnification to conserve flux under focusing and defocusing. Thermal emission and absorption are then computed along each traced line by solving the radiative transfer equation, producing synthetic radio maps from 40 to 800 MHz. Applied to a coronal model with prescribed electron density, temperature, and magnetic field, the framework reproduces the quiet-Sun background spectra broadly consistent with observations when propagation effects are included, while active-region brightness remains less accurately reproduced. These results establish a physics-based framework for generating low-frequency quiet-Sun synthetic images, enabling quantitative comparisons with interferometric observations and assessment of propagation effects on observed coronal morphology.