Using the 11-year Solar Cycle to Predict the Heliosheath Environment at Voyager 1 and 2

Abstract:

As Voyager 2 moves further into the heliosheath, the region of subsonic solar wind plasma in between the termination shock and the heliopause, it has observed an increase of the magnetic field strength to large values, all while maintaining magnetic flux conservation. Dr. Burlaga will present these observations in the 2015 AGU Fall meeting (abstract ID: 59200). The increase in magnetic field strength could be a signature of Voyager 2 approaching the heliopause or, possibly, due to solar cycle effects. In this work we investigate the role the 11-year solar cycle variations as well as magnetic dissipation effects have on the heliosheath environments observed at Voyager 1 and 2 using a global 3D magnetohydrodynamic model of the heliosphere. We use time and latitude-dependent solar wind velocity and density inferred from SOHO/SWAN and IPS data and solar cycle variations of the magnetic field derived from 27-day averages of the field magnitude average of the magnetic field at 1 AU from the OMNI database as presented in Michael et al. (2015). Since the model has already accurately matched the flows and magnetic field strength at Voyager 2 until 93 AU, we extend the boundary conditions to model the heliosheath up until Voyager 2 reaches the heliopause. This work will help clarify if the magnetic field observed at Voyager 2 should increase or decrease due to the solar cycle. We describe the solar magnetic field both as a dipole, with the magnetic and rotational axes aligned, and as a monopole, with magnetic field aligned with the interstellar medium to reduce numerical reconnection within the heliosheath, due to the removal of the heliospheric surrent sheet, and at the solar wind – interstellar medium interface. A comparison of the models allows for a crude estimation of the role that magnetic dissipation plays in the system and whether it allows for a better understanding of the Voyager 2 location in the heliosheath.