Astronomy

Blowing in the Solar Wind

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Science  26 Oct 2012:
Vol. 338, Issue 6106, pp. 444
DOI: 10.1126/science.338.6106.444-a
CREDIT: NASA

Launched in 1977, the two Voyager spacecraft have traveled deep into space, but they are still transmitting data back to Earth. Having crossed the termination shock, the point where the solar wind is abruptly slowed down by the interstellar medium surrounding the solar system, both spacecraft are currently in the outermost layer of the heliosphere—the heliosheath. Richardson and Wang report recent data from the plasma instrument on Voyager 2, which crossed the termination shock in 2007 as solar activity was approaching its minimum. Previous data had shown a decrease in the solar wind density at the position of Voyager 2 6 months after it crossed the termination shock; now data from 2011 and 2012 reveal an increase in the plasma density back to the levels observed just after termination shock crossing, before the decrease was observed. These results may signal the end of solar minimum conditions in the heliosheath.

Astrophys. J. 759, L19 (2012).

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