Abstract
Abstract. A correlation between solar wind speed at Earth and the amount of magnetic field line expansion in the corona was verified in 1989 using 22 years of solar and interplanetary observations. We trace the evolution of this relationship from its birth 15 years earlier in the Skylab era to its current use as a space weather forecasting technique. This paper is the transcript of an invited talk at the joint session of the Historical Astronomy Division and the Solar Physics Division of the American Astronomical Society during its 224th meeting in Boston, MA, on 3 June 2014.
Highlights
This is the 25th anniversary of the origin of the Wang– Sheeley–Arge (WSA) model
What is the WSA model? It is a procedure for deriving solar wind speed from maps of the photospheric magnetic field
In 2011, Vic Pizzo and his colleagues succeeded in making the WSA-ENLIL model operational at the National Oceanic and Atmospheric Administration (NOAA)/SEL, by that time called the NOAA Space Weather Prediction Center (NOAA/SWPC)
Summary
This is the 25th anniversary of the origin of the Wang– Sheeley–Arge (WSA) model. It occurred in 1989 when there was no internet as we know it, no cell phones, and no Google, and Apple stock was selling for $45 per share. It is a procedure for deriving solar wind speed from maps of the photospheric magnetic field. If the flux tube that guided the flow flares out, the distant speed is slow. If the flux tube remains focused, the distant speed is fast. The amount of expansion is obtained from a current-free extension of the photospheric field
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