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Mystery: Gas from sun heads in wrong direction

SOHO tracks a cloud of gas heading back to the sun.
SOHO tracks a cloud of gas heading back to the sun.  

By Richard Stenger
CNN Sci-Tech

(CNN) -- In defiance of expectations, clouds of solar gas have been observed falling back into the sun. The puzzling behavior could shed light on the mysterious magnetism of the sun, which helps protect planet Earth from lethal cosmic rays.

European astronomers have spotted the enigmatic eruptions on numerous occasions using a powerful sun-watching satellite observatory.

Mostly they take place during times of intense solar activity, characterized by the presence of many sunspots. The inflows have started about 1.7 million miles (2.7 million kilometers) from the sun's surface, a distance equivalent to twice the diameter of the star

For unknown reasons, they are able to fight against the powerful solar wind, which pushes gas and ions away from the sun at speeds of about 75 miles per second (120 km/second).

"I was stunned when I saw the first movies showing these inflows," said Bernard Fleck, a scientist with the European Space Agency. Using the Solar and Heliospheric Observatory (SOHO), a joint ESA-NASA sun-watching satellite, he and others first witnessed the strange phenomenon several years ago.

"Before the discovery with SOHO, no one had any idea that gas could travel the wrong way and be pushed back toward the sun."

Solar scientists have combed over data from thousands of observations to look for patterns. In some circumstances, they found 20 inflows each day on the left side of the sun, following a lull of two weeks, then a similar number of inflows on the right side of the sun.

Traveling along magnetic lines, protruding loops of erupting solar material can short-circuit, merge into new loops and collapse toward the sun, which suggests that the sun's magnetic field is responsible.

But an explanation remains elusive.

"We are seeing something opposite to what we expected," said Neil Sheeley, a U.S. Naval Research Laboratory solar scientist who helped put together solar gas movies from SOHO images.

Sheeley and colleagues theorize that the inflows take place as the sun recycles its magnetic field into its atmosphere.

The process influences the interplanetary magnetic field that stretches beyond our planet and shields terrestrial life from destructive cosmic rays from other stars.


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