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Models and observations indicate that the impact of matter accreting onto thesurface of young stars produces regions at the base of accretion columns, inwhich optically thin and thick plasma components coexist. Thus an accuratedescription of these impacts requires to account for the effects of absorptionand emission of radiation. We study the effects of radiation emerging fromshock-heated plasma in impact regions on the structure of the pre-shockdownfalling material. We investigate if a significant absorption of radiationoccurs and if it leads to a pre-shock heating of the accreting gas. Wedeveloped a radiation hydrodynamics model describing an accretion columnimpacting onto the surface of a Classical T Tauri Star. The model takes intoaccount the stellar gravity, the thermal conduction, and the effects of bothradiative losses and absorption of radiation by matter in the non localthermodynamic equilibrium regime. After the impact, a hot slab of post-shockplasma develops at the base of the accretion column. Part of radiation emergingfrom the slab is absorbed by the pre-shock accreting material. As a result, thepre-shock accretion column gradually heats up to temperatures of $10^5$ K,forming a radiative precursor of the shock. The precursor has a thermalstructure with the hottest part at $T \approx 10^5$ K, with size comparable tothat of the hot slab, above the post-shock region. At larger distances thetemperature gradually decreases to $T \approx 10^4$ K.

Effects of Radiation in Accretion Regions of Classical T Tauri Stars: Pre-heating of accretion column in non-LTE regime