Michael Schirber at Space.com:
Constantly buffeting the Earth and its satellites, the solar wind can gust from 750,000 to 1.5 million mph. Astronomers would like to predict the dramatic changes in this constant barrage of charged particles so as to better protect the craft that orbit Earth.
Recent research shows that the solar speeds can be accurately measured by observing a relatively deep layer of the Sun’s atmosphere – far beneath where the winds are thought to originate.
In what could be a boon to space weather forecasts, scientists discovered a relation between solar wind speed and fluctuations in the chromosphere – a region a few thousand miles thick on the outer surface of the Sun.
More here.