Solar Cinema
January 20, 2000 -- What's 1.4 million
kilometers across, covered with magnetic spots, and the
hottest box office attraction in the Solar System? (Hint:
It's bigger than Tom Hanks.)
With
solar maximum just around the corner, the Sun is putting on
a show that rivals the most sizzling Hollywood thrillers.
Powerful solar flares and coronal mass ejections happen
almost every day. You can't see them with the naked eye, but
the European Space Agency and NASA have a front row seat,
thanks to the Solar and Heliospheric Observatory (SOHO).
SOHO monitors solar activity from a permanent vantage point
1.5 million kilometers ahead of the Earth in a halo
orbit around the L1
Lagrangian point. Unlike an Earthbound observer, it can
see the Sun 24 hours a day.
Above: On January 18, 2000, the space-based Solar
and Heliospheric Observatory Extreme
Ultraviolet Imaging Telescope captured these images of a
huge eruptive prominence escaping the Sun. Click on the
animation for a close-up view of the figure "8"
shaped eruption visible in the lower left corner of the
animation.
On January 18, 2000, SOHO spotted a
spectacular prominence, pictured above in an animation
spanning a 24 hour period. At maximum, the prominence was
about 100 times wider than the Earth.
Prominences are loops of magnetic fields
with hot gas trapped inside. Sometimes, as the fields become
unstable, the they will erupt and rise off of the Sun in
just a few minutes or hours. Beautiful prominences like
these become more common as we approach solar maximum.
When will the solar maximum actually take
place? Recent work by David Hathaway, a solar physicist at
the Marshall Space Flight Center, and his collaborators
indicate that the solar activity will peak around the middle
of the year 2000.
"Our predictions have consistently
targeted 2000 as the beginning of solar maximum," said
Hathaway in a recent interview, "but the latest numbers
suggest that the peak sunspot count in 2000 will be a bit
lower than expected. The projected peak is comparable to,
but lower than the peaks of the last two maxima (in 1989 and
1978). That would put all three of the recent sunspot maxima
in the same class -- above average compared to all the
sunspot cycles since the mid 1700's."
Above: By combining data about geomagnetic
activity during the previous solar cycle with sunspot counts
for the current cycle, David Hathaway and collaborators are
able to predict when the next sunspot maximum will occur. [Click
here for details]. According to their results, the
sunspot number -- and other forms of solar activity -- will
peak beginning in mid-2000. The dotted lines above and below
the solid curve line indicate the prediction curve's range
of error.
"The sunspot maximum is usually a
broad peak. There is a two or three year period when
activity is quite high. I expect solar activity to be
highest in 2000 and 2001, and then in 2002 it may decline
back to where we [were] in 1999."
During this period of heightened solar activity, the Sun
puts on a nearly non-stop show. For instance, just one week
ago SOHO captured another sequence of prominences. This
time, the Extreme
Ultraviolet Imaging telescope was observing in a mode
with a higher-than-usual telemetry rate, due to the fact
that the Large Angle Spectrometric Coronagraph (LASCO)
instrument had its doors closed in anticipation of
spacecraft maneuvers. The resulting movies (click on the
image for a Quicktime animation) are awesome. If eruptions
like these are directed toward the Earth they can cause a
significant amount of aurora and other geomagnetic activity.
For more information about space weather
see http://SpaceWeather.com.
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 HQ office of Space Science.
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