Mapping the sun: SwRI-led team develops probabilistic model to map the sun’s far side

A research team led by the Southwest Research Institute (SwRI) has developed a probabilistic modelling framework that significantly improves how solar activity is mapped across both the visible and far-side hemispheres of the Sun

Published in The Astrophysical Journal Supplement Series, the study introduces an enhanced Surface Flux Transport (SFT) model that systematically evaluates far-side helioseismic data to eliminate false positives, known as “ghost active regions”, providing a cleaner dataset to forecast solar cycles and space weather.

Mapping the sun: Overcoming the far-side blind spot and “Ghost” sunspots

Because the Sun rotates on its axis approximately once every 27 days, half of its surface remains obscured from direct Earth-based observation at any given moment. Unpredicted sunspots rotating into Earth’s line of sight frequently disrupt solar activity, according to models.

To monitor this hidden hemisphere, helioseismologists analyse acoustic waves travelling through the solar interior to detect far-side magnetic structures.

However, raw acoustic data often generate false positive detections. Acoustic signals sometimes indicate a major magnetic active region on the far side that fails to materialise when the area rotates into direct view.

To resolve these “ghost active regions,” the SwRI framework assigns a statistical probability to each potential far-side active region based on its unique physical properties before incorporating it into the SFT model. The team calibrated this framework using whole-Sun surface maps compiled from 2010 to 2014, combining Earth-based observations with spaceborne assets deployed on the opposite side of the Sun.

Applications for space weather forecasting and sun mapping

By filtering out artefact signals while preserving genuine far-side active regions, the updated SFT model constructs a far more accurate global map of the Sun’s magnetic field dynamics.

Lead author Dr Bibhuti Jha and co-author Dr Lisa Upton (both of SwRI’s Solar System Science and Exploration Division) emphasise that reliable global magnetic mapping is essential for predicting solar cycles and anticipating space weather events, such as coronal mass ejections, that can disrupt satellite communications, power grids, and orbital operations on Earth.