How does the solar wind change with time?


Yes it does, but there are several different components to it that change differently in time. The 'high speed streams' are produced by solar storms that come and go on the surface more or less in step with the sunspot cycle. But over longer times, even the sunspot cycle seems to come and go over the centuries. In fact, in the 1600s there were no sunspot cycles recorded at all, and very few sunspots, so this suggests that during at least this hundred year period, there may have been no high-speed streams and major episodes of solar mass loss. Stars themselves evolve and change, and our Sun like other stars of its type that have been studied, may have gone through many episodes when its solar wind was far stronger or far weaker than anything we have observed in the last 50 years since the wind was discovered. The strength of the solar wind seems to be determined by the degree of magnetic activity on the Sun, the speed of the sun's rotation, and whether the surface of the Sun convects like a hot porage as it does now. These factors change very slowly over millions and even billions of years, so the solar wind we see today is probably not that different than what it was long ago. Still, short term changes can occur measured in centuries or in thousands of years and we seem to be in such an episode of 'active solar winds' today. But it could all change with the next solar cycle..or its failure to materialize!


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All answers are provided by Dr. Sten Odenwald (Raytheon STX) for the
NASA IMAGE/POETRY Education and Public Outreach program.