Magnetized Plasma Near the Heliopause: Voyager 1 Measurements and Theoretical Modeling

Voyager 1 (V1) "early" penetration into the local interstellar medium (LISM) raises challenging questions about the structure of the heliopause (HP) and the magnetic field behavior on its both sides. In this paper, we analyze the results of our previous simulations in an attempt to understand the spacecraft observations paying particular attention to the heliocentric distance at which V1 crossed the HP and the corresponding changes in the heliospheric magnetic field (HMF) direction. The issues related to a dissipative/resistive structure of the HP are discussed together with the globally unstable behavior of this tangential discontinuity separating the solar wind from the LISM. It is shown that the solar cycle model by Pogorelov et al. (2009a) gives the interstellar magnetic field elevation and azimuthal angles consistent with the current V1 observations. We further demonstrate that the presence of solar cycle effects results in a Rayleigh Taylor-type instability of the HP nose, which in turn makes it possible for the LISM plasma to penetrate deep into the inner heliosheath, making it considerably narrower. We argue that the solar cycle is a substantial ingredient necessary to launch the above-mentioned instability. The reasons for that are periodic decreases in the HMF strength on the inner side of the HP.