Constraining the Properties of the Multicomponent Local Interstellar Medium: MHD-kinetic Modeling Validated by Voyager and New Horizons Data

Abstract

We introduce the first solar-cycle simulations from our 3D, global MHD-plasma/kinetic-neutrals model, where both hydrogen and helium atoms are treated kinetically, while electrons and helium ions are described as individual fluids. Using Voyager/PWS observations of electron density up to 160 au from the Sun for validation of several different global models, we conclude that the current estimates for the proton density in the local interstellar medium (LISM) need a revision. Our findings indicate that the commonly accepted value of 0.054 cm−3 may need to be increased to values exceeding 0.07 cm−3. We also show how different assumptions regarding the proton velocity distribution function in the outer heliosheath may affect the global solution. A new feature revealed by our simulations is that the helium ion flow may be significantly compressed and heated in the heliotail at heliocentric distances exceeding ∼400 au. Additionally, we identify a Kelvin–Helmholtz instability at the boundary of the slow and fast solar wind in the inner heliosheath, which acts as a driver of turbulence in the heliotail. These results are crucial for inferring the properties of the LISM and of the global heliosphere structure.