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October
14, 1999: Beginning in late September, a continuing series
of minor to moderate geomagnetic storms have triggered aurorae
along the northern tier of U.S states and may have affected some
public power systems operating at high northern latitudes. These
events were caused by high-speed material streaming out from
areas on the sun known as coronal holes. This
week we can expect more of the same as another coronal hole
rotates into position to send high-speed solar wind particles
toward our planet. Space weather forecasters expect moderate
levels of aurorae, shortwave radio disruptions, and power grid
fluctuations at high latitudes for at least the next three days.
It's not all bad news, though. The increased levels of solar activity will likely trigger dazzling auroral displays at mid-latitudes. Sky watchers in the continental U.S. will be treated to sights normally reserved for residents of higher latitudes. Another piece of good news is that increased atmospheric drag at solar maximum acts as a scavenger and helps clean out space debris from low-Earth orbit.
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," says Hathaway, "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. |
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Related Stories Surfing Magnetic Waves in the Solar Atmosphere July 8, 1999. How the Solar Wind Gets Up to Speed Solar Flares Show Their True Colors June 2, 1999. New research points to a common mechanism for spectral behavior in Solar Flares "Cool" microflares could be solar hot spots May 31, 1999. Secret of coronal heating may be multitude of tiny blasts. Finding the smoking gun before it fires March 9, 1999. Physicists discover a new tool for predicting solar eruptions. Recent stories on the August '99 Eclipse Decrypting the Eclipse - August 6, 1999, scientists around the world explore the possible and mysterious effect of eclipses on the motion of Foucault's pendulum. There goes the Sun - August 5, 1999, features general information about the August 11, 1999 solar eclipse, including the effect of eclipses on the birds and the bees, and eclipses on other planets. Audio eclipse may fill the sky - August 4, 1999 story on investigations of ionization and radio propagation in Earth's atmosphere during the eclipse Peering through a Hole in the Sky - June 17, 1999 story on exotic gravity measurements to be carried out during the eclipse |
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