Abstract

When a light beam enters a scattering-dominated medium, the radiation is isotropized. Part of the radiation goes backwards, leading to non-monotonicity in the radiation energy density profile inside this medium. There arises a local maximum at which the energy density at a scattering albedo \({\sim}1\) is severalfold greater than that without scattering at the same extinction. This effect is studied numerically in one-dimensional and two-dimensional simulations. It is demonstrated that a local maximum of the radiation energy density arises in the medium, whose value depends on the optical depth of the region. This effect can manifest itself, for example, when the radiation from a gamma-ray burst (GRB) enters heated regions in the interstellar medium. The presence of scattering in the GRB radiation generation region, near the front of strong shocks, affects the radiation pattern. The structure of such shocks is remarkable for the presence of a preshock preheating tail. Strong scattering in this region leads to the escape of a significant fraction of the radiation sideways and backwards in the shock reference frame, forming additional tails in the angular distribution of GRB radiation after the relativistic transformation to the laboratory frame. This effect is also studied numerically in three-dimensional simulations.

中文翻译：

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软伽马射线暴发射中的强散射效应

摘要

当光束进入以散射为主的介质时，辐射是各向同性的。部分辐射向后传播，导致该介质内辐射能量密度分布的非单调性。出现一个局部最大值，在该最大值处，散射反照率\({\sim}1\)处的能量密度比相同消光处没有散射的能量密度大几倍。通过一维和二维模拟对这种效应进行数值研究。结果表明，介质中出现辐射能量密度的局部最大值，其值取决于该区域的光学深度。例如，当伽马射线暴（GRB）的辐射进入星际介质中的加热区域时，这种效应就会显现出来。靠近强冲击波前端的伽玛射线暴辐射产生区域中存在的散射会影响辐射方向图。这种激波的结构因其预激预热尾部的存在而引人注目。该区域的强散射导致激波参考系中很大一部分辐射向侧面和向后逃逸，在相对论变换到实验室参考系后，在GRB辐射的角分布中形成额外的尾部。这种效应也在三维模拟中进行了数值研究。