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Using polar coronal hole observations to improve solar wind forecasting

Presentation #301.06 in the session Predicting solar wind properties across the heliosphere with integrated modeling efforts (empirical or first-principles).

Published onOct 20, 2022
Using polar coronal hole observations to improve solar wind forecasting

Models of the heliospheric magnetic field and solar wind are driven by global solar photospheric magnetic field maps. However, the critical polar regions are typically not well observed. We explore the use of observed polar coronal holes to constrain the flux distribution within the polar regions of global solar magnetic field maps. Global magnetic maps, generated by the Air force Data Assimilative Photospheric flux Transport (ADAPT) model, are modified to enforce field unipolarity thresholds both within and outside observed coronal hole boundaries. The polar modified and unmodified maps are used to drive Wang-Sheeley-Arge (WSA) models of the corona and solar wind. The WSA predicted coronal holes are compared with the observations, and solar wind predictions at the WIND and Ulysses spacecraft are also used to provide context for the new polar modified maps. We find that modifications of the polar flux typically improve both the coronal hole and solar wind predictions. In addition, we investigate the importance of active region magnetic fields in setting the boundary of polar coronal holes, determining that they have at least as much impact as the polar fields themselves. Based on these results, we comment on the importance and need for consistent polar and far side field observations that will be pioneered by Solar Orbiter, as drivers for solar wind predictions. This work utilizes data produced collaboratively between the Air Force Research Laboratory (AFRL) and the National Solar Observatory. The ADAPT model development is supported by AFRL.

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