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Solar Cycle Update

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see captionMarch 22, 2000 -- On New Years Day, 2000, technophiles breathed a sign of relief when the feared Y2K computer bug proved to be a dud. Cell phones still worked, bank accounts were balanced, airplanes took off and landed safely. But was the reprieve only temporary? The solar maximum -- dubbed the "real Y2K problem" by some pundits -- is due to arrive in mid-2000. By triggering power blackouts and communications disruptions, solar activity could cause some of the same problems that raised fears at the beginning of the year.

Solar activity is indeed on the rise, says Dr. David Hathaway, a solar physicist at NASA’s Marshall Space Flight Center in Huntsville, Alabama, but there may be nothing to worry about. Judging from recent sunspot counts, the 2000 solar maximum will be slightly less spectacular than sunspot peaks in 1978 and 1989. Those maxima caused occasional problems with satellites and power blackouts, but nothing that threatened civil order or world finance. Been there. Done that.

Above: This animation shows a coronal mass ejection (CME) erupting from the Sun on March 19-20, 2000. Around the time of the solar maximum, CMEs like these are observed nearly every day. When they are directed at Earth they can cause geomagnetic disturbances including beautiful auroras. These data were captured by the C3 coronagraph on the NASA/ESA Solar and Heliospheric Observatory (SOHO)

A 1996 panel of solar physicists reached the consensus that the peak sunspot number in 2000 would register 160, plus or minus 30. Currently at 130, the maximum is "clinging to the bottom side" of their predictions. The "day-to-day the numbers fluctuate wildly" and there is a slim possibility of an intensification in the next few months, says Hathaway.

"Perhaps it's really going to take off," he said, but so far there's no evidence of a cataclysmic burst of activity.

Still, Hathaway rejects the argument of those who, by scrutinizing recent activity levels, allege that the cycle has already peaked. "I don't believe it for a moment."

In the course of a solar maximum, Hathaway says

the "frequency of solar eruptions is dramatically increased." During a solar minimum, a week or more will pass without any solar eruptions. Now, nearing the apex of the cycle, there are multiple eruptions every day. This week is a good example. Since March 17 there have been more than four "M-class" solar flares. According to the NOAA Space Environment Center, M-class eruptions cause high-frequency radio blackouts on the sunlit side of the Earth and degrade low-frequency navigation signals for tens of minutes affecting maritime and general aviation positioning. On February 6 the brightest solar flare of the current cycle erupted. The "X-class" event (10 times bigger than an M-class flare) caused radio blackouts for hours.

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Above: NOAA's GOES satellites have detected X-ray bursts from 5 "M-class" solar flares since March 18, 2000. The red curve is the X-ray flux registered by the GOES-8 satellite in the 1-8 Angstrom band.

The expectation that scientists can isolate the precise date and time of a solar maximum is a common misconception, says Hathaway. In reality there is no single episode. Instead, the solar maximum will last over an extended period of time.

Throughout this period of heightened activity, sky-watchers can expect to see "more displays of aurora -- Northern Lights." Not everyone should anticipate brilliant auroral demonstrations, though. Hathaway anticipates activity, "confined to northern latitudes unless a really big storm comes along." The effects of previous solar maximums have been
visible as far south as the Panhandle of Florida. Hathaway remembers seeing aurora in 1980 while in Boulder, Colorado - a relatively southern latitude.

What incites this mushrooming activity?

Sunspots are cooler areas on the sun's surface surrounded by twisted magnetic fields. Solar flares, the biggest eruptions in the solar system, derive energy from these magnetic fields. A sudden change in the fields can release ample energy to fuel powerful solar flares and coronal mass ejections. The latter can travel as fast as 2000 km/s, and both can transport particles and radiation to Earth in minutes. When aimed at Earth they can trigger geomagnetic storms that disrupt communication systems, imperil satellites, affect weather patterns, and cause auroras. Although minuscule relative to the total energy of the Sun, flares can unleash more than 10 million times the amount of energy released from an erupting volcano..

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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.

Trying to survive on the sun's boiling surface is not an easy mission. Hathaway says sunspots "last weeks at the longest," the record length stretching a mere 6 months. Despite their fleeting existence, certain active regions are sites of repeated eruptions. In recent days sunspot groups 8910 and 8906 (NOAA designations) have produced recurrent flares.

Scientists are not yet able to accurately predict solar flares and coronal mass ejections. Hathaway says that current technology allows space weather forecasters to "get a good idea" by looking at the magnetic fields around the sunspots. If they locate a leader spot and a spot of opposite polarity, called a delta spot, materializes, Hathaway says there's a good chance that "something's going to happen."

Stay tuned to Science.nasa.gov for more updates about solar and geomagnetic activity as the solar cycle nears it peak.

Note: SOHO is a cooperative project between the European Space Agency (ESA) and NASA. The spacecraft was built in Europe for ESA and equipped with instruments by teams of scientists in Europe and the USA.

Web Links

Solar Smoke Rings - a series of coronal mass ejections dazzle scientists.

Solar Cinema - Cool movies of a recent solar prominence.

SpaceWeather.com -follow the latest events on the Sun

Coronal Mass Ejections -from the Marshall Space Flight Center

SOHO home page -real-time images, screen savers, and more