Modeling the Global Coronal Field with Simulated Synoptic Magnetograms from Earth and the Lagrange points L3, L4 and L5

The solar photospheric magnetic flux distribution determines the global structure of the solar corona and heliosphere. Regular full-disk photospheric magnetogram data are therefore essential to our ability to model and forecast heliospheric phenomena such as space weather. However, our spatio-temporal coverage of the photospheric field is currently limited by our single vantage point at/near Earth. In particular, the polar fields define the large-scale structure of the corona and heliosphere but each pole is unobservable for > 6 months per year. Here we model the possible effect of full-disk magnetogram data from the Lagrange points L4 and L5, each extending longitude coverage by 60 degrees. Adding data also from the more distant point L3 extends longitudinal coverage much further. The additional vantage points also improve the visibility of the globally influential polar fields. Using a flux-transport model for the solar photospheric field we model full-disk observations from Earth/L1, L3, L4 and L5 over a solar cycle, construct synoptic maps using a novel weighting scheme adapted for merging magnetogram data from multiple viewpoints, and compute potential-field models for the global coronal field. Each additional viewpoint significantly improves the performance of the maps and models with particular improvement at polar latitudes, the main source of the fast solar wind.