Solar Wind Weakest in 40 Years

The Ulysses spacecraft, a collaborative venture by NASA and the ESA that was launched in 1990, has confirmed that the solar wind, the stream of particles that pours out of the Sun, is the weakest it has ever been in forty years. The weakening of the solar wind has pushed the heliosphere, the area in where the outgoing solar wind and the incoming plasma from interstellar space meet, closer in than usual. In other words, the solar system is shrinking.

Dave McComas, an executive director of the Southwest Research Institute in the US says that the solar wind protects the solar system from cosmic ray particles. There has already been a 20 per cent increase in the number of cosmic ray electrons arriving at the Earth from outside the solar system. While most of these electrons are stopped by the Earth's magnetic field and so do not affect people on Earth, they could affect astronauts in other parts of the solar system, such as Mars.

Richard Marsden, ESA's mission manager for Ulysses, the solar wind has been declining for years. It is now 20 per cent weaker than it was in 1995, the previous low point.

Professor Jay Pasachoff at Williams College in the US says that the solar cycle completely shut down in the 18th century. Pasachoff says that this may happen again. However, the magnetic orientation of one Sunspot that has recently been sighted indicates that it may be the first of a new sunspot cycle.

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