"These massive blasts are likely to become more frequent in 2000 as the
Sun moves into the most active year of its 11-year cycle."
(Solar cycle #23 peaks (ideally) in May 2000, but it could hit as early
as December 1999. Its level of activity is expected to be TEN TIMES that of
the last few decades.)
Sun's fiery S-shapes foretell massive solar blasts
By Deborah Zabarenko
WASHINGTON, March 9 (Reuters) - Fiery S-shapes on the Sun's surface can help
predict when potentially dangerous and disruptive blasts of electrically
charged gas will come hurtling toward Earth, scientists said on Tuesday.
Such massive solar explosions pack the force of billions of nuclear blasts and
can knock out power grids, damage satellites and scramble communications
networks, so forecasting them is becoming increasingly important.
Until now, scientists have only been able to tell that one of these big solar
blasts had already occurred, which still gave Earth two to three days to
prepare while the blast traveled toward the planet.
But the discovery of the telltale S shape means forecasters can detect the
blast even before it happens, giving Earth up to five or six days to get
ready.
The S-shapes, called sigmoids, were glimpsed by the Japanese Yohkoh spacecraft
and explained at a briefing at NASA headquarters on Tuesday.
"The sigmoid is like a loaded gun that we now know has a high probability of
going off," said Aphonse Sterling, of the Institute of Space and Astronautical
Science (ISAS) of Japan.
"We have found a strong correlation between an S-shaped pattern on the Sun ...
and the likelihood that an ejection will occur from that region within days,"
Sterling said.
These massive blasts, which scientists call coronal mass ejections (CMEs), are
likely to be more frequent in 2000 as the Sun moves into the most active year
of its 11-year cycle of activity.
CMEs are the largest explosions in the solar system, hurling up to 10 billion
tons of gas into space at speeds of 1 billion to 2 billion miles an hour (1.6
billion to 3.2 billion km an hour), several times a day. Not every CME is
aimed at Earth.
Sigmoids are "a very twisted, slinky-like structure" related to the Sun's
underlying magnetic field, according to Sarah Gibson of the University of
Cambridge, England, who also participated in the briefing.
Not every CME is presaged by a sigmoid, the scientists said, but most sigmoids
signal very large CMEs.
The Yohkoh images show an S-shape as the precursor to a CME and an arch-shape
as the sign that the blast has already occurred, the scientists said.
The National Aeronautics and Space Administration is planning a mission called
STEREO, with two spacecraft that will make three-dimensional images of CMEs
and other solar structures.
