The solar wind is losing its bluster. It hasn't slowed down, but it's not as hot or as dense as it used to be. Scientists aren't sure what the reason is. But they do know that the change could make space travel a little more hazardous.
The solar wind is a constant flow of charged particles from the Sun. When they hit Earth, these particles create the shimmering curtains of light known as the aurorae -- the northern and southern lights.
Last year, the Ulysses spacecraft measured the solar wind all the way around the Sun. It found that the pressure of the solar wind had dropped by about 20 percent over the past decade. In fact, it was the lowest that scientists have seen -- a result of fewer particles in the wind.
Earth's atmosphere blocks the solar wind, so scientists only began studying it when the first interplanetary probes were launched almost 50 years ago. So a flagging and stiffening solar wind could be part of a regular cycle, just like the shift in winds brought about by the changing seasons on Earth.
A thinner solar wind will allow more cosmic rays to enter the solar system, where they can damage spacecraft and expose astronauts to more radiation.
Those of us who stay on Earth won't suffer any ill effects, though, because the atmosphere and magnetic field stop cosmic rays. In fact, about the only effect we might notice is that the aurorae might get a little fainter -- deprived of the blustery solar wind.
Script by Damond Benningfield, Copyright 2008
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