VARIABILITY OF THE NEUTRAL HYDROGEN DENSITY DISTRIBUTION DUE TO SOLAR-CYCLE RELATED EFFECTS

The influence of the realistic solar cycle variability of the solar Lyman-a radiation pressure and ionisation rate on the distribution of interstellar hydrogen within heliosphere is analysed. The temporal evolution of density is discussed and compared with the results of the static, classical ''hot'' model computed for various sets of ionisation rate and radiation pressure values. It is shown that the density variations are especially pronounced along the downwind direction and result in density waves smearing out only beyond about 60 AU, while in the upwind region non-negligible modulations extend to about 20 AU. Discussion of the influence of the hydrogen density variation on the interplanetary Lyman-a backscattered glow observed from 1 AU is provided along with some comments on the applicability of the static, classical ''hot'' model as an interpretation tool for these observations.