Transition Region Near the Heliopause: Modeling Results from the Voyager Mission Perspective

Abstract:

Voyager 1 (V1) observations show that the transition region separating the solar wind (SW) from the local interstellar medium (LISM) is the venue of a complicated interplay between micro- and macroscopic phenomena. We show that the heliopuse is subject to Rayleigh-Taylor and Kelvin-Helmholtz instabilities, which add fine structure to the transition region. We demonstrate the heliopause structure allows magnetic connection of different regions inside it to either the SW or LISM, which may be an explanation of variations in the galactic and anomalous cosmic ray fluxes observed by Voyager. We investigate the magnetic field behavior near the heliopause in the directions of V1 and Voyager 2 (V2), and identify magnetic flux tubes which may be due to magnetic reconnection at some distance from the heliopause crossing points. Differences in the plasma and magnetic field distributions in the V1 and V2 directions are discussed and compared with Voyager observations. Numerical simulations are performed with the Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS) using a new approach where pickup ions (PUIs) are treated as a separate fluid and special boundary conditions are implemented for PUIs at discontinuities. We show numerical results of PIC simulations of turbulence generated by PUIs in the outer heliosheath and discuss them in the context of V1 observations of the LISM turbulence spectrum.