Improvement in the prediction of solar wind conditions using near-real time solar magnetic field updates

The Wang-Sheeley model is an empirical model that can predict the backgroun d solar wind speed and interplanetary magnetic field (IMF) polarity. We mak e a number of modifications to the basic technique that greatly improve the performance and reliability of the model. First, we establish a continuous empirical function that relates magnetic expansion factor to solar wind ve locity at the source surface. Second, we propagate the wind from the source surface to the Earth using the assumption of radial streams and a simple s cheme to account for their interactions. Third, we develop and apply a meth od for identifying and removing problematic magnetograms from the Wilcox So lar Observatory (WSO). Fourth, we correct WSO line-of-sight magnetograms fo r polar field strength modulation effects that result from the annual varia tion in the solar b angle. Fifth, we explore a number of techniques to opti mize construction of daily updated synoptic maps from the WSO magnetograms. We report on a comprehensive statistical analysis comparing Wang-Sheeley m odel predictions with the WIND satellite data set during a 3-year period ce ntered about the May 1996 solar minimum. The predicted and observed solar w ind speeds have a statistically significant correlation (similar to 0.4) an d an average fractional deviation of 0.15. When a single (6-month) period w ith large data gaps is excluded from the comparison, the solar wind speed i s correctly predicted to within 10-15%. The IMF polarity is correctly predi cted similar to 75% of the time. The solar wind prediction technique presen ted here has direct applications to space weather research and forecasting.