Improving Multiday Solar Wind Speed Forecasts. Issue 9 (9th September 2022)

• Record Type: Journal Article
• Authors: Elliott, H. A.; Arge, C. N.; Henney, C. J.; Dayeh, M. A.; Livadiotis, G.; Jahn, J.‐M.; DeForest, C. E.
• Is Part Of: Space weather. Volume 20:Issue 9(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-09-09
• Subjects: solar wind -- forecast -- space weather -- geoeffective -- speed; Space environment -- Periodicals; 551.509992
• DOI: 10.1029/2021SW002868
• Languages: English
• ISSNs: 1542-7390

Abstract

Abstract: We analyze the residual errors for the Wang‐Sheeley‐Arge (WSA) solar wind speed forecasts as a function of the photospheric magnetic field expansion factor ( f p ) and the minimum separation angle ( d ) in the photosphere between the footpoints of open field lines and the nearest coronal hole boundary. We find the map of residual speed errors are systematic when examined as a function of f p and d . We use these residual error maps to apply corrections to the model speeds. We test this correction approach using 3‐day lead time speed forecasts for an entire year of observations and model results. Our methods can readily be applied to develop corrections for the remaining WSA forecast lead times which range from 1 to 7 days in 1‐day increments. Since the solar wind density, temperature, and the interplanetary magnetic field strength all correlate well with the solar wind speed, the improved accuracy of solar wind speed forecasts enables the production of multiday forecasts of the solar wind density, temperature, pressure, and interplanetary field strength, and geophysical indices. These additional parameters would expand the usefulness of Air Force Data Assimilative Photospheric Flux Transport‐WSA forecasts for space weather clients. Plain Language Summary: We significantly improve the accuracy of the Wang‐Sheeley‐Arge solar wind speed forecasts by correcting the speeds using the residual speed errors as a function of two quantities. Those two quantities are how close the magnetic field line footpoints are to the coronal hole boundary, and how much the magnetic field lines in the corona bend. Our improved solar wind speed forecasts have the potential to enable multiday forecasts of the solar wind density, temperature, and interplanetary magnetic field strength since these quantities correlate well with the solar wind speed. Forecasts of these additional quantities are needed to improve multiday space weather forecasts. Key Points: Residual Wang‐Sheeley‐Arge solar wind speed errors are systematic versus both expansion factor and angle to the coronal hole boundary We improve solar wind speed forecast by correcting the model speeds using these systematic residual speed errors Improved solar wind speed forecast accuracy can enable multiday solar wind density, temperature, and field strength forecasts