Inferring the Interstellar Magnetic Field Direction from Energetic Neutral Atom Observations of the Heliotail

Determining the magnitude and direction of the interstellar magnetic field (BISM) is a longstanding problem. To date, some methods to infer the direction and magnitude have utilized best fit models to the positions of the termination shock and heliopause measured by Voyager 1 and 2. Other models use the circularity of the IBEX Ribbon assuming a secondary energetic neutral atom (ENA) mechanism. Previous studies have revealed that the BISM organizes the orientation of the heliotail with respect to the solar meridian. Here, we propose a new way to infer the direction of the BISM based on ENA observations of the heliotail. IBEX observations of the heliotail have revealed high-latitude lobes of enhanced ENA flux at energies >2 keV. Analyses showed that the high latitude lobes are nearly aligned with the solar meridian, while also exhibiting a rotation with solar cycle. We show using steady state solar wind conditions that the inclination of the lobes reproduced with commonly used values for the angle (αBV) between BISM and the interstellar flow in the hydrogen deflection plane (40 deg. < αBV < 60 deg.) is inconsistent with the IBEX ENA observations. We report that 0 deg. < αBV < 20 deg. is required to reproduce the heliotail lobe inclinations observed by IBEX. Additionally, we find that the variation of the solar magnetic field magnitude with solar cycle causes the longitudinal rotation of the lobes observed by IBEX by affecting the inclination of the lobes.