The solar wind (SW) and interplanetary magnetic field (IMF) have a significant influence on the near‐Earth space environment. In this study we evaluate and compare forecasts from two models that predict SW and IMF conditions: the Hakamada‐Akasofu‐Fry (HAF) version 2, operational at the Air Force Weather Agency, and Wang‐Sheeley‐Arge (WSA) version 1.6, executed routinely at the Space Weather Prediction Center. SW speed (Vsw) and IMF polarity (Bpol) forecasts at L1 were compared with Wind and Advanced Composition Explorer satellite observations. Verification statistics were computed by study year and forecast day. Results revealed that both models’ mean Vsw are slower than observed. The HAF slow bias increases with forecast duration. WSA had lower Vsw forecastobservation difference (F‐O) absolute means and standard deviations than HAF. HAF and WSA Vsw forecast standard deviations were less than observed. Vsw F‐O mean square skill rarely exceeds that of recurrence forecasts. Bpol is correctly predicted 65%–85% of the time in both models. Recurrence beats the models in Bpol skill in nearly every year forecast day category. Verification by “event” (flare events ≤5 days before forecast start) and “nonevent” (no flares) forecasts showed that most HAF Vsw bias growth, F‐O standard deviation decrease, and forecast standard deviation decrease were due to the event forecasts. Analysis of single time step Vsw increases of ≥20% in the nonevent forecasts indicated that both models predicted too many occurrences and missed many observed incidences. Neither model had skill above a random guess in predicting Vsw increase arrival time at L1.


Mechanical and Aerospace Engineering

Publication Status

Free Access

Keywords and Phrases

forecast verification, interplanetary magnetic field, solar wind

Document Type

Article - Journal

Document Version

Final Version

File Type





© 2023 American Geophysical Union, all rights reserved

Publication Date

16 December, 2010