Stand by for Outages, Radio Disruptions and Auroras—the Sun Has Its 11-Year Itch
03/03/1980 at 01:00 AM EST
The sun is 330,000 times larger than the earth, and even its slightest variations, if they last long, can have a profound impact on human life. There is no immediate danger of the sun's blinking out—scientists generally agree it will last for at least five billion more years—but the activity on its vast surface does rise and fall spectacularly in 11-year periods known as sunspot cycles. The latest cycle is now reaching its peak of sunspot and solar flare activity—a period called the Solar Maximum Year—which will cause short-term disruptions in communications on this planet and possible long-term consequences for weather, crops and living conditions. David M. Rust, a solar physicist, is directing an unprecedented worldwide program by the National Science Foundation and NASA to study this phenomenon. Born in Denver, Rust, 40, earned his B.S. from Brown University and his Ph.D. in astrophysics from the University of Colorado. Previously associated with several observatories, Rust has been senior staff scientist at American Science and Engineering Inc. in Cambridge, Mass. since 1974. He lives in Silver Spring, Md. with his wife, Gail, and his two children from a previous marriage. Nearby is the Goddard Space Flight Center where the $80 million Solar Maximum Mission satellite was assembled and the international research project is headquartered. Rust talked about the sun's big 1980 show with Frank W. Martin of PEOPLE.
What is so dramatic about this particular Solar Maximum Year?
All signs indicate it will be the second most intense period of solar activity since man started keeping records in the 17th century. This time we have more and better equipment, especially the space satellite, and more people. There are 300 to 400 solar physicists—about half of all there are in the world—observing the sun from more than 60 points on a 24-hour basis and working on associated projects. In solar activity there are so many things happening that no one observer can cover everything.
Why does solar activity go in cycles, and why 11 years?
There is no good explanation. We know the sun's powerful magnetic field and gases churning inside control the cycles, but we don't understand how.
When did this Maximum Year begin?
We assigned it a beginning date of August 1, 1979, because on that date we had a favorable alignment of the space observatories. A number of very large flares began appearing in September. Just as we didn't know precisely when the Maximum Year would begin, we don't know precisely when it will subside. It could last as long as five years. Round-the-world observations will go on for 19 months, and we will be studying the findings for years.
Why do you think this will be the second most intense period in recorded history?
Because the number of sunspots at the beginning of the Maximum Year was so high. We predict from that the same way you might predict that because the horse Secretariat broke so strongly from the gate he won't fade in the stretch.
What was the most intense Solar Year?
The Super Bowl of solar activity took place from 1957 to 1959, during the peak of Cycle 19.
How was the earth affected?
The intense magnetic disturbances produced surges estimated at 2,700 volts in the Bell System's transatlantic telephone cables, causing transmissions to suddenly alternate between faint whispers and loud squawks. There were power outages, and displays of the northern lights—or aurora borealis—were visible as far south as Providence, R.I. With even larger flares this time around, we may be able to see auroras even in the Southern U.S.
What is a sunspot?
It is a dark, cool area on the surface of the sun with a very high magnetic field. The magnetic lines of force pop out from the surface in a loop that reenters at another point. That's why sunspots occur in pairs, one with a negative field, the other with a positive field.
Are sunspots related to solar flares?
We're not sure. But flares always occur near sunspots, which proves that flares are really caused by some instability in a strong magnetic field. A flare is a sudden increase of temperature and brightness on the solar surface, like a bolt of lightning, except that it may last from 10 minutes to a day. Flares are the most exciting aspect of the sun because they affect the earth so suddenly and dramatically—especially killer flares. We might see two or three killer flares this year.
Do killer flares really kill?
If an astronaut were working outside an Apollo spacecraft, he could receive 10 times the lethal dose of radiation. Even if he were in the module, he'd probably get a lethal dose. But the ozone layer in the earth's atmosphere, as well as water and other atoms, forms a very effective barrier. Nobody should skip a trip to the beach for fear of exposure.
Then how do killer flares affect earth?
Take the first week of August 1972, a high solar activity period. There were three killer flares that week. Aside from minor blackouts and intense northern-lights displays, we got unverified reports that a large number of the mines laid in Haiphong harbor in North Vietnam suddenly exploded. Apparently, they were magnetically sensitive and were triggered by the huge magnetic fields associated with the flares.
How are radio waves affected?
Normal radio communications are often seriously disrupted. During the Cuban missile crisis of 1962 some big solar flares reportedly cut off for a time the Air Force's ability to talk to its planes. Ham radio operators love periods of maximum solar action. Their signals travel by bouncing off the ionosphere, an electrically charged layer in the earth's upper atmosphere. Radiation from the sun's expanded activity increases the density of the ionosphere and makes ham signals bounce even farther.
Can flares be predicted?
Yes, with about 20 percent accuracy now—but the science is only in its infancy. Radiation reaches the earth in eight minutes, traveling at the speed of light. The first to arrive are the X-rays. The atomic particles come 20 minutes to hours later, depending on their energy. The solar flare forecast center in Boulder, Colo. tries to get warnings out to the Air Force and the Federal Aeronautics Administration within one minute of detection. Planes can then be routed to lower altitudes to avoid the increased radiation.
Did the sun cause Skylab's demise?
Absolutely. Radiation from solar activity heated up and expanded the outer atmosphere more than was predicted. The gases created drag on the craft, cumulatively slowing it down and decaying its orbit.
How does solar activity affect weather?
All we know for sure is that it gets colder without normal solar activity. The rest is strongly debated. For instance, droughts in the Southwest seem to occur every 22 years, which is every other solar cycle. Some think there is a connection. Others see a link between solar activity and the thickness of tree rings, indicating more growth when there is more activity on the sun.
Has there ever been a period of no sunspots or flares?
It was big news five years ago when careful analyses of historical records showed there were no sunspots from 1645 to 1715. That coincided with the coldest part of what is called the Little Ice Age. It was very cold in Europe; some lakes froze that never had before, and growing seasons were shorter.
What would happen if the sun's surface became quiet again?
If the average mean temperature of the earth dropped by one degree—as it did during the Little Ice Age—farmers would be greatly affected, to give just one example. The area suitable for growing wheat in the United States would probably move south by hundreds of miles.
Does solar activity seem to be increasing or decreasing?
In the past I don't think we could have answered that because of weather and atmospheric interference. But the satellite we have launched is monitoring the solar constant—the sun's total energy output. If it's increasing, we'll have a warmer earth. Over time, that could mean a melting of the polar ice caps. Then I suppose the oceans would rise and many coastal cities would go under.
What is the safe way to observe this year's bumper crop of sunspots and solar flares?
I recommend looking through a special telescope equipped with a solar filter. If you look through smoked glass or exposed film you can burn out your retina and go blind. The northern lights, however, are perfectly safe for the naked eye, and if we get killer flares there could be auroras visible anywhere in the country. In any case, it will be a grand show.