Polarity-Resolved Far-Side Magnetograms Based on Helioseismic Measurements

Abstract

Understanding and monitoring solar active regions is essential for operational space-weather forecasting and improved solar dynamo modeling. This requires comprehensive 360-degree observations of the Sun. While space-weather forecasting has long relied successfully on high-quality observations of the Earth-facing hemisphere, a critical gap remains due to the lack of direct, continuous magnetic field measurements of far-side active regions, particularly magnetic field strength, polarity configurations, and related parameters. We present a methodology for inferring magnetic field distributions of active regions in helioseismic maps of the far hemisphere. The analysis focuses on identifying the magnetic polarities of opposing components of a helioseismic signature and applying stable, continuous polarity assignment to large-scale magnetic structures derived from such maps. These helioseismic signatures reliably resolve strong active regions, especially those that later appear as major rotation regions when they rotate into Earth view. Polarity boundaries are identified by analyzing the bimodal longitudinal variance profile of the seismic signal within each region, after which Hales law is applied to establish east-west ordering consistent with the solar cycle. The method produces polarity-resolved far-side magnetograms suitable for integration with near-side observations, enabling construction of full-Sun magnetic boundary conditions for coronal and solar wind modeling and providing a critical step toward improved heliospheric simulations and operational forecasting.