Speaker
Description
Accurate prediction of the ambient solar wind at Earth is a key requirement for space-weather forecasting but is limited by uncertainties in coronal boundary conditions and, to a lesser extent, heliospheric transport. We present a solar wind forecasting approach that uses near-Earth in situ solar wind observations to estimate the inner boundary condition for the Heliospheric Upwind eXtrapolation with Time dependence (HUXt) model. In terms of the forecast at Earth, this method is similar to 27-day recurrence forecasting. However, unlike recurrence, it produces a solution throughout the heliosphere which can potentially be used to improve CME propagation estimates and forecasting at a range of in-ecliptic heliospheric locations. To test this forecast method, daily hindcasts are generated over a 15-year interval spanning 2008–2022. Performance is evaluated and directly compared with forecasts generated by the standard operational forecast approach; namely magnetogram-based estimates using the Wang–Sheeley–Arge (WSA) coronal model. The InSitu-HUXt hindcasts achieve median solar wind speed errors around 65 km s$^{-1}$ for lead times up to 27 days. WSA-HUXt hindcasts are most accurate around 4-days lead time, with an MAE of around 85 km s$^{-1}$. More diagnostic metrics show that this is partly because InSitu-HUXt naturally produces a bias-free prediction, whereas WSA-HUXt currently over-predicts the occurrence of high-speed streams in the solar wind by around 30%. Thus InSitu-HUXt provides a valuable independent method to forecast near-Earth solar wind conditions and can be used even when magnetogram data is unavailable, providing forecast resilience.
| Numerical model | HUXt |
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