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Scientists find way to look behind the sun |
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April 19, 2000
WASHINGTON, APR 18 (AP) - Scientists have found a way to peek behind the sun to see whether dangerous solar storms are brewing that could affect Earth.
The process may make it possible to predict the appearance of sunspots before they rotate around from the far side of the sun, giving time to protect Earth satellites and other systems that may be damaged by the radiation.
Sunspots produce increased radiation, disturbing the so-called space weather in ways that can damage electric and communications systems on Earth and even cause satellites to change their orbits.
Now a team of European researchers has developed a system they believe offers the chance of detecting sunspots while they are still on the back side of the sun.
Their findings are in a paper scheduled to be published in the May 1 issue of the journal Geophysical Research Letters.
The number of sunspots rises and falls in an 11-year cycle and the peak of that cycle is occurring this year, raising concerns among many utilities and satellite operators.
A solar surge in March 1989 has been blamed for a massive power blackout in Canada, leaving 6 million people without electricity.
And increased solar radiation can affect radio communications and may warm the Earth's upper atmosphere, causing it to expand into the region occupied by some satellites, slowing them down and potentially changing their orbits.
Seeking ways to get advance warning, the team led by Jean-Loup Bertaux of France's National Center for Scientific Research studied a type of solar radiation called Lyman alpha.
A sunspot acts like a spotlight shining radiation into space and L-alpha radiation can be detected because it brightens hydrogen atoms there.
Bertaux's team found that instruments on the SOHO satellite, positioned between Earth and the sun, could detect the "illumination" of hydrogen atoms beyond the sun by L-alpha radiation.
An unusually bright area would indicate the presence of the increased radiation from a sunspot, they concluded, allowing researchers to determine its position on the back side of the sun and predict when it would rotate around to face the Earth.
The sun rotates every 27 days, meaning warnings could come weeks in advance.
Their report comes just a month after another team reported a separate system for forecasting solar disturbances.
That group, led by Douglas Braun of Northwest Research Associates in Boulder, Colorado, reported in the journal Science that they had spotted telltale ripples on the face of the sun that indicate when a disturbance is under way on the back side.
Braun and his co-author, solar physicist Charles Lindsey, were also using data from SOHO, the Solar and Heliospheric Observatory.
They found that waves moving through the great gas ball of the sun have a characteristic that is caused by disturbances on the far side.
Bertaux's team also included researchers at Finnish Meteorological Institute.
SOHO is a joint mission of European Space Agency and the National Aeronautics and Space Administration. It is stationed 930,000 miles (1.5 million kilometers) from the Earth, near a point where the gravity of Earth and sun balance each other.
Geophysical Research Letters is published by the American Geophysical Union. --- On the Net: American Geophysical Union: http://www.agu.org France's National Center for Scientific Research: http://www.cnrs.fr/index.html
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