SOLAR-CYCLE MODULATION OF THE INTERSTELLAR HYDROGEN DENSITY DISTRIBUTION IN THE HELIOSPHERE

A new approach taking explicitly into account time dependent variation s of the solar radiation pressure and ionisation rate is developed for more realistic description of the distribution of the hot (similar to 8000 K) interstellar hydrogen gas within the heliosphere. It is shown that the solar cycle-related variabilities cause temporal modulation of the hydrogen density patterns, manifested by propagation of density waves smearing out only beyond about 20 AU and 60 AU in the upwind an d downwind directions, respectively. Density variations induce modulat ion of the size of hydrogen cavity by similar to 15% around the mean v alue, affect (mainly in the antiapex direction) the location of the ma ximum emissivity region (MER) contributing to the Lyman-alpha backscat tered glow, and lead to a significant temporal modulation of the upwin d-to-downwind Lyman-alpha intensity ratio as seen from the inner Solar System.