Modeling magnetic polarity distributions of solar activity from its helioseismic signature

We propose to develop, as an inverse problem, the facility to assign appropriate polarities to magnetic flux distributions whose absolute magnetic field strengths, |B|, are well mapped but whose local polarities (north/south) are unknown. Standard diagnostics in helioseismology, such as computational helioseismic holography, give us good maps of |B|, of active regions in the Sun’s far hemisphere, but are cluless as to where the local magnetic polarity is north or south. As a basis for assigning appropriate polarities to the elements of helioseismic signatures, we turn to the Hale Polarity Law, following leads introduced by N. Arge and C. Henney. The magnetic flux densities of newly emerging magnetic flux ropes are strongly bipolar. The Hale Law observes that when these fluxes are large, the leading (westward) component of the magnetic signature is consistently of south-magnetic polarity in the Sun’s northern hemisphere and of north-magnetic polarity in the Sun’s southern hemisphere—currently. This pattern reverses in both hemispheres every eleven years after a brief period—a year or two—of virtual magnetic hibernation. The next reversal is due in the early 2020s. The Hale Law renders the solution straight-forward when the emerging flux is a single, well-defined flux rope, as it often is in fact. The challenge looms when the emerging flux is more complex, resulting in multiple photospheric bipoles, sometimes with the trailing pole of one component compacted against the leading pole of some other, for example. This is important for practical applications in space-weather forecasting, because opposing magnetic poles of this vintage often interact violently, giving rise to flares and coronal mass ejections, impacting space weather at Earth—when these regions rotate into the Sun’s near hemisphere.