Heliospheric Response to Different Possible Interstellar Environments

At present, the heliosphere is embedded in a warm low density interstellarcloud that belongs to a cloud system flowing through the local standard of restwith a velocity near ~18 km/s. The velocity structure of the nearestinterstellar material (ISM), combined with theoretical models of the localinterstellar cloud (LIC), suggest that the Sun passes through cloudlets ontimescales of < 10^3 - 10^4 yr, so the heliosphere has been, and will be,exposed to different interstellar environments over time. By means of amulti-fluid model that treats plasma and neutral hydrogen self-consistently,the interaction of the solar wind with a variety of partially ionized ISM isinvestigated, with the focus on low density cloudlets such as are currentlynear the Sun. Under the assumption that the basic solar wind parametersremain/were as they are today, a range of ISM parameters (from cold neutral tohot ionized, with various densities and velocities) is considered. In responseto different interstellar boundary conditions, the heliospheric size andstructure change, as does the abundance of interstellar and secondary neutralsin the inner heliosphere, and the cosmic ray level in the vicinity of Earth.Some empirical relations between interstellar parameters and heliosphericboundary locations, as well as neutral densities, are extracted from themodels.Comment: 24 pages, 9 figures, 2 table