Evolution of the Solar Lyα Line Profile during the Solar Cycle. II. How Accurate Is the Present Radiation Pressure Paradigm for Interstellar Neutral H in the Heliosphere?

Abstract

Abstract Following the derivation of a more accurate model of the evolution of the solar Lyα line with the changing solar activity by Kowalska-Leszczynska et al. (IKL18) than the formerly used model by Tarnopolski & Bzowski (ST09), we investigate the potential consequences that adoption of the resulting refined model of radiation pressure has for the model distribution of interstellar neutral (ISN) H in the inner heliosphere and on the interpretation of selected observations. We simulated the ISN H densities using the two alternative radiation pressure models and identical models of all other factors affecting the ISN H distribution. We found that during most of the solar cycle, the IKL18 model predicts larger densities of ISN H and pickup ions than ST09 in the inner heliosphere, especially in the downwind hemisphere. However, the density of ISN H at the termination shock estimated by Bzowski et al. obtained using ST09 does not need revision, and the detection of ISN D by IBEX is supported. However, we point out the existence of a considerable absorption of a portion of the solar Lyα spectral flux inside the heliosphere. Therefore, the model of radiation pressure for ISN H is still likely to need revision, and hence the available models of ISN H are not self-consistent.