08/21/1995 07:00:00

Caltech Observatory Sees Start of New Solar Sunspot Cycle

PASADENA—The first sunspot in the new sunspot cycle was identified on Saturday, August 12, by astronomers at the California Institute of Technology's Big Bear Solar Observatory in Big Bear City, California. The new sunspot marks the end of the sun's quiescent period and the beginning of a new surge of sunspot activity.

"This makes us happy," said Hal Zirin, professor of astrophysics at Caltech and director of the Big Bear Solar Observatory. "The sun is a lot more interesting to study when things are going on."

Sunspots are relatively dark spots that typically appear in groups on the surface of the sun. They are associated with strong magnetic fields and with solar flares, and follow an approximately 11-year cycle of increasing activity followed by a slow decline into a quiescent period. Early in the cycle, sunspots appear rarely and at relatively high solar latitudes around 30 to 35 degrees, then increase in frequency and appear at lower latitudes until they reach sunspot maximum. After this peak in activity, the number of sunspots slowly declines, and they appear ever closer to the sun's equator until they reach a relatively quiet phase called sunspot minimum.

There is typically some overlap between successive sunspot cycles. As the last sunspots of one cycle appear near the equator, at latitudes of about 7 degrees, the next cycle starts again with sunspots near 30 degrees, but with the magnetic polarity of the new spots reversed.

That's exactly the point the sun is at now; it has been in a quiescent period through much of 1994 and this year, with a few spots showing up near the equator. The new sunspot photographed on Saturday appeared at a solar latitude of 21 degrees, and its magnetic polarity is opposite to that seen over the last decade, a key to identifying it as the manifestation of the start of a new cycle.

This new sunspot appeared a bit earlier than astronomers expected. Typically, as a solar cycle winds down, late bursts of sunspot activity will appear near the equator before the new cycle starts. Scientists had seen these late pulses of sunspots in 1984, but saw little late activity this time and therefore expected an early beginning to the new cycle, but not this early.

Sunspots have effects far beyond the sun itself, so while solar astronomers are excited by this news, people in many other fields are keenly interested as well. Solar flares often occur above sunspots, and can disrupt radio communications on earth and sometimes even cause widespread power outages. Flares also cause the colorful celestial displays known as the northern (or southern) lights, and cause unusual behavior in satellites, such as increased drag and disabled orientation.

Sunspots in the new cycle should rapidly become more common and reach a high level of activity in 1998 or 1999.

Written by John Avery