Magnetic Dissipation Effects on the Flows within the Heliosheath

Abstract:

We investigate the effect that magnetic dissipation has on the flows within the heliosheath (HS), the subsonic plasma in between the termination shock (TS) and the heliopause (HP). We use a global 3D multi-fluid magnetohydrodynamic (MHD) model of the heliosphere, which has a grid resolution of 0.5 AU within the heliosphere along both Voyager 1 and Voyager 2 trajectories. We describe the solar wind magnetic field as a monopole, to remove the heliospheric current sheet, with the magnetic field aligned with that of the interstellar medium (ISM) to diminish any numerical reconnection at the ISM – solar wind interface. This configuration of the solar wind magnetic field also reduces any numerical magnetic dissipation effects in the HS. We compare our model to the same model describing the solar wind magnetic field as a dipole. In the dipole case, there is an intrinsic loss of magnetic energy near the heliospheric current sheet (HCS) due to reconnection. This reconnection is numerical since we do not include real resistivity in the model. The comparison of the two models will allow for an estimation of the effects of reconnection in the HS since there is no numerical dissipation of the magnetic field in the monopole model. We compare steady state solutions and the role magnetic dissipation has on the global characteristics of the heliosphere. We find that the monopole model of the solar wind magnetic field removes the asymmetry observed in the TS and predicted for the HP. Furthermore, the TS is considerably closer to the Sun in the monopole model due to the build up of magnetic filed at the HP. We also investigate magnetic dissipation effects in the 11-year solar cycle variations of the solar wind in a 3D time-dependent model. This model includes 3D latitudinal and temporal variations of the solar wind density and velocity taken from SOHO/SWAN and IPS data from 1990 to 2012 as described in Provornikova et al. 2014. We additionally include a time varying magnetic field obtained from the OMNI database. We compare both models to observations along Voyager 1 and Voyager 2 and discuss whether magnetic dissipation is a significant process affecting the flows within the HS.