The helioglow is the fluorescence of interstellar atoms inside the heliosphere, where they are excited by the solar EUV emission. So far, the helioglow of interstellar H and He has been detected. The helioglow features a characteristic distribution in the sky, which can be used to derive the properties of both interstellar neutral (ISN) gas and the solar wind. This requires a simulation model capable of catching with sufficient realism the essential coupling relations between the solar and interstellar factors. The solar factors include the solar wind flux and its variation with time and heliolatitude, as well as the heliolatitude and time variation of the solar EUV output. The ISN gas inside the heliosphere features a complex distribution function, which varies with time and location. The paper presents the first version of a WawHelioGlow simulation model for the helioglow flux using an optically thin, single-scattering approximation. The helioglow computations are based on a sophisticated kinetic treatment of the distribution functions of interstellar H and He provided by the (n)WTPM model. The model takes into account the heliolatitudinal and spectral variations of the solar EUV output from observations. We present a formulation of the model and the treatment of the solar spectral flux. The accompanying Paper II illustrates details of the line-of-sight evolution of the elements of the model and a brief comparison of results of the WawHelioGlow code with selected sky maps of the hydrogen helioglow, obtained by the SWAN instrument on board the Solar and Heliospheric Observatory mission.

日光是日光层内星际原子的荧光，在那里它们被太阳 EUV 发射激发。到目前为止，已经探测到星际H和He的日光。日光在天空中具有特征分布，可用于推导出星际中性 (ISN) 气体和太阳风的特性。这需要一个能够以足够真实的方式捕捉太阳和星际因素之间基本耦合关系的模拟模型。太阳因素包括太阳风通量及其随时间和日纬度的变化，以及太阳极紫外输出的日纬度和时间变化。日光层内的ISN气体具有复杂的分布函数，随时间和位置而变化。本文介绍了第一个版本的 WawHelioGlow 模拟模型，该模型使用光学薄的单散射近似值来计算日光通量。日光计算基于对 (n)WTPM 模型提供的星际 H 和 He 分布函数的复杂动力学处理。该模型考虑了来自观测的太阳 EUV 输出的日向纬度和光谱变化。我们提出了模型的公式和太阳光谱通量的处理。随附的论文 II 详细说明了模型元素的视线演变，并简要比较了 WawHelioGlow 代码的结果与选定的氢日光天空图（由太阳和日光层上的 SWAN 仪器获得）天文台任务。