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 ObservatoryExtreme 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.
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.
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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.
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."
Right: A January 10, 2000 SOHO EIT image showing an eruptive prominence on the Sun. Click for an animation of this eruption.
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
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.
SpaceWeather.com -Science news and information about the Sun-Earth environment.
NOAA Space Environment Center -official site for space weather forecasts and information
Solar and Heliospheric Observatory -home page