A Twisted Tale of Sunspots
- Source: Space Science News
February 29, 2000
A Twisted Tale of Sunspots
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Two large sunspots near the Sun's central meridian have developed
complex magnetic fields. If solar flares erupt from these regions
Earth could be in for stormy space weather.
The NOAA Space Environment Center is forecasting a 70% chance of
significant M-class solar flares from at least one of the two large
sunspots currently visible on the solar disk. Because of their
placement on the Sun, like a double-barreled ray gun, these two
sunspot groups are likely to produce solar flares and coronal mass
ejections (CMEs) aimed toward Earth. Stormy space weather could be on
the way sometime during the next 72 hours.
Solar flares are the biggest explosions in the solar system. A typical
eruption can release the same amount of energy as millions of
100-megaton hydrogen bombs all exploding at the same time. The energy
source for solar flares is the Sun's magnetic field. Whenever the
magnetic field around a sunspot group becomes twisted and sheared,
like a stretched and twisted rubber band, an explosive release of
energy could be just around the corner.
Space weather forecasters noticed on February 28, 2000, that both of
the large active regions 8882 and 8891 (pictured above) had developed
relatively complicated "beta-gamma" type magnetic fields. Most
sunspots come in pairs with a magnetic field that looks somewhat like
that of a bar magnet. Magnetic lines of force emerge from one spot
(the north pole), loop overhead, and come back down to the other
member of the pair (the south pole). This is called a bipolar or
"beta-type" field. "Beta-gammas" are bipolar sunspot groups that are
so complex that no single, continuous line can be drawn between spots
of opposite polarity. The energy stored in the twisted magnetic field
lines serves as fuel for solar flares and CMEs. Eruptions occur when
the fields rearrange to form a simpler, lower-energy configuration.
Intense M-class and X-class flares can overload electrical power grids
and cause blackouts if operators do not take precautions. Satellites
can be damaged or even destroyed when their electronics are saturated
by charged particles from large flares. A large and famous space storm
in 1989 induced electrical currents on the ground that caused a
failure in the Hydro-Quebec electric power system. This prevented 6
million people in Canada and the US from having electricity for over 9
hours. The same storm caused the atmosphere to inflate and dragged the
NASA's Long Duration Exposure Facility satellite to a lower orbit
earlier than expected.
Not every Earth-directed eruption causes big problems, however. On
February 17, 2000, a solar explosion sent a large coronal mass
ejection (CME) directly toward our planet. Satellite operators and
power technicians braced for the worst, but not much happened. The
Earth's magnetosphere did a good job protecting our planet from the
interplanetary shock wave.
It remains to be seen whether active regions 8882 and 8891 will
produce flares and geomagnetic disturbances. If the spots remain quiet
for a few more days, the Sun's rotation will carry them westward and
remove Earth from the proverbial cross hairs. The art of predicting
solar flares is still rudimentary, so it's hard to say what will
happen in the coming days. Tune in to SpaceWeather.com for daily
updates about the development of these active regions and for
information about other space weather activity.
SOHO (the Solar and Heliospheric Observatory) is a mission of
international cooperation between NASA and the European Space Agency.
It is managed by the Goddard Space Flight Center for the NASA
Headquarters Office of Space Science. For more news and information
about space weather, please see SpaceWeather.com. Technical
information about current space weather conditions may be found at the
NOAA Space Environment Center.
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