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تسجيل مستخدم جديدWawHelioGlow: a model of the heliospheric backscatter glow. I. Model definition
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The helioglow is a 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 have been detected. The helioglow features a characteristic distribution in the sky, which can be used to derive both the properties of interstellar neutral gas and those of the solar wind. This requires a simulation model capable of catching with a sufficient realism the essential coupling relations between the solar factors and interstellar. 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 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 onboard the SOHO mission.
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The helioglow is a fluorescence of interstellar atoms inside the heliosphere, where they are excited by the solar EUV. Because the mean free path between collisions for the interstellar gas is comparable to the size of the heliosphere, the distributi
on function of this gas inside the heliosphere strongly varies in space and with time and is non-Maxwellian. Coupling between realistically modeled solar factors and the distribution function of interstellar neutral gas is accounted for in a helioglow model that we have developed. WawHelioGlow is presented in the accompanying Paper I. Here, we present the evolution of the gas density, solar illumination, helioglow source function, and other relevant parameters building up the helioglow signal for selected lines of sight observed at 1 au. We compare these elements for various phases of the solar cycle and we present the sensitivity of the results to heliolatitudinal anisotropy of the solar EUV output. We assume a realistic latitudinal anisotropy of the solar wind flux using results from analysis of interplanetary scintillations. We compare the simulated helioglow with with selected maps observed by the SOHO/SWAN instrument. We demonstrate that WawHelioGlow is able to reproduce fundamental features of the sky distribution of the helioglow. For some phases of the solar cycle, the model with an anisotropy of the solar EUV output better reproduces the observations, while for other phases no EUV anisotropy is needed. In all simulated cases, the solar wind anisotropy following insight from interplanetary scintillation measurements is present.
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