The Sun's Dynamic Influence on the Outer Heliosphere, the Heliosheath, and the Local Interstellar Medium

Abstract

The Sun has been observed for many years to be a dynamic influence in the heliosphere, and as the Voyager missions have continued long after achieving their original goals of observing the major planets they have provided the first in situ observations of the effects of solar activity in the heliosheath (HS), and the nearest portions of the local Interstellar Medium (LISM). Comparing these observations with models provides key insights. We employ two three-dimensional (3D) time-dependent models that simulate the propagation of shocks, other specific features, and the background solar wind throughout the heliosphere, starting with the solar background and solar event boundary conditions near the Sun at 2.5 Rs. The Hybrid Heliospheric Modeling System with Pickup Protons (HHMS-PI) is a 3D time- dependent Magnetohydrodynamic (MHD) simulation. HAFSS (HAF Solar Surface) is a 3D time-dependent kinematic simulation. Comparing our models with the observations indicates that solar effects are seen in the heliosphere, the HS, and the LISM in in-situ spacecraft measurements of plasma, magnetic field, energetic particles, cosmic rays, and plasma waves. There is quantitative agreement (at ACE, Ulysses, VI, V2) with data (e.g., solar wind, IMF, Ulysses SWICS pickup protons (PUPs)). Propagating shocks are slowed due to PUPs. The 3D locations of solar events and of various spacecraft are key to understanding the 3D propagation and timing of shocks, other specific features, and gradients throughout the heliosphere, HS, and LISM.