Solar Wind Loses Power, Hits 50-year Low
Not by Fire but by Ice
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23 Sep 08 - Excerpts from NASA announcement.
"In a briefing yesterday at NASA headquarters, solar physicists announced that the solar wind is losing power.
"The average pressure of the solar wind has dropped
more than 20% since the mid-1990s," says Dave McComas of the Southwest
Research Institute in San Antonio, Texas. "This is the weakest it's been
since we began monitoring solar wind almost 50 years ago."
"Curiously, the speed of the million mph solar wind hasn't decreased much—only 3%. The change in pressure comes mainly from reductions in temperature and density. The solar wind is 13% cooler and 20% less dense.
Thirteen percent cooler. Do you
suppose that this might
"What we're seeing is a long term trend, a steady decrease in pressure that began sometime in the mid-1990s," explains Arik Posner, NASA's Ulysses Program Scientist in Washington DC.
"How unusual is this event?
"It's hard to say. We've only been monitoring solar wind since the early years of the Space Age—from the early 60s to the present," says Posner. "Over that period of time, it's unique. How the event stands out over centuries or millennia, however, is anybody's guess. We don't have data going back that far."
"Flagging solar wind has repercussions across the entire solar system—beginning with the heliosphere.
"The heliosphere is a bubble of magnetism springing from the sun and inflated to colossal proportions by the solar wind. Every planet from Mercury to Pluto and beyond is inside it. The heliosphere is our solar system's first line of defense against galactic cosmic rays. High-energy particles from black holes and supernovas try to enter the solar system, but most are deflected by the heliosphere's magnetic fields.
"The solar wind isn't inflating the heliosphere as much as it used to," says McComas. "That means less shielding against cosmic rays."
Losing our shielding against
cosmic rays! This is exactly
"In addition to weakened solar wind, "Ulysses also finds that the sun's underlying magnetic field has weakened by more than 30% since the mid-1990s," says Posner. "This reduces natural shielding even more."
"Unpublished Ulysses cosmic ray data show that, indeed, high energy (GeV) electrons, a minor but telltale component of cosmic rays around Earth, have jumped in number by about 20%.
"These extra particles pose no threat to people on Earth's surface. Our thick atmosphere and planetary magnetic field provide additional layers of protection that keep us safe.
They may not cause a threat …
yet, but as our planetary
"But any extra cosmic rays can have consequences. If the trend continues, astronauts on the Moon or en route to Mars would get a higher dose of space radiation. Robotic space probes and satellites in high Earth orbit face an increased risk of instrument malfunctions and reboots due to cosmic ray strikes. Also, there are controversial studies linking cosmic ray fluxes to cloudiness and climate change on Earth. That link may be tested in the years ahead.
A higher dose of space radiation
“poses no threat to people on
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