TIME: Almanac 1995

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<text id=89TT1724> <link 90TT1936> <link 89TT0036> <title> July 03, 1989: Fury On The Sun </title> <history> TIME--The Weekly Newsmagazine--1989 July 03, 1989 Great Ball Of Fire:Angry Sun </history> <article> <source>Time Magazine</source> <hdr> SCIENCE, Page 46 COVER STORY Fury on The Sun </hdr><body> Once worshiped as a god, earth's star is revealing the secrets of its awesome power By Leon Jaroff Strolling outside Arizona's Kitt Peak National Observatory during a work break, staff observer Paul Avellar at first thought the angry red glow in the night sky was caused by forest fires. Then, seeing a greenish fringe and vertical streamers stretching like ribbons above the horizon, he realized what was happening. He raced to a telephone and called his wife and friends, awakening them and insisting they share the view. "A chance like this doesn't come along very often," says Avellar. "To see the northern lights is very humbling and awe-inspiring. You realize the sun is just going about its business and making our nighttime sky glow without any trouble at all. It makes you wonder what would happen if the sun ever really got mad." Some 93 million miles away, the sun was, at the very least, agitated. In early March, an area of sunspots large enough to contain 70 earth-size planets had come into view around the eastern rim (to astronomers, the eastern edge of the sun is to the left, as viewed from earth.) of the glowing orb. Created by intense magnetic fields and cooler than the surrounding gases, the sunspots were visible as dark blemishes on the fiery surface. Just as astronomers were turning their attention to the mottled region, a bright spot suddenly appeared in its midst. It spread like a prairie wildfire, glowing white hot on the sun's yellow face and quickly expanding to cover hundreds of thousands of square miles. The monster blotch was an unusually large solar flare, a stupendous explosion that belched radiation and billions of tons of matter far into space. The great flare, and its coterie of sunspots, was an unmistakable signal. It heralded the imminent arrival of the solar maximum: the period every eleven years or so when the sun reaches its peak levels of activity and pointedly reminds earth dwellers of its awesome power. At maximum, the sun bombards the planet with radiation and particles, causing unusually brilliant auroras, communications blackouts and power failures. But it also gives scientists a fresh opportunity to solve some of the mysteries surrounding the star that provides the earth with energy, drives the weather and sustains life itself. During a maximum, marked by a jump in the number of sunspots and flares, giant loops of incandescent gases, called prominences, proliferate, shooting tens of thousands of miles above the solar surface, sometimes hanging suspended for months. The solar corona, the halo around the sun visible during total eclipses, becomes fuller and brighter; great blobs of the corona, containing billions of tons of hot gas, occasionally burst free, shooting into space at speeds as high as 2 million m.p.h. And the earth's upper atmosphere, pummeled by solar particles, is laced by electrical currents of as much as a million amperes. These in turn create powerful magnetic fields that raise havoc below. Because the previous maximum occurred in late 1979, astronomers had targeted 1991 as the year when solar frenzy would again peak. But the sun is notably capricious. While the intervals between maximums average eleven years, some have been as short as seven, others as long as 17. Ever since the sun began revving up three years ago toward the next maximum, its activity has mounted with unprecedented speed. "It is the fastest riser on record," says Ron Moore, an astronomer at NASA's Marshall Space Flight Center in Huntsville, Ala. So fast, in fact, that astronomers are betting on 1990 or perhaps even later this year, instead of 1991, as the beginning of the maximum. And what a maximum it could be. Despite the ferocity of the March flares, Moore warns, "this cycle is still in its early phase. It's got quite a way to go." Solar buffs are speculating it might approach the violence reached by the 1957-58 maximum, which touched off five disruptive geomagnetic superstorms and vivid auroral displays. Says astronomer Donald Neidig at the National Solar Observatory outpost on Sacramento Peak, near Sunspot, N. Mex.: "We can't rule out a record breaker." In anticipation of the fireworks, astronomers scheduled a two-week, worldwide solar-observation period during the second half of June. The project was timed to benefit from the observations of the Solar Maximum Mission satellite (nicknamed Solar Max) before it plunges to its death. Lofted into earth orbit in 1980 to monitor the sun's activity, the satellite is gradually descending and will probably re-enter the earth's atmosphere in November and be incinerated. Solar Max's readings of the sun's activity were coordinated with observations made all over the world by ground-based telescopes and instruments mounted on high-flying rockets. A hundred solar centers around the globe were linked by an electronic-mail network designed to provide the latest data on the sun's behavior. A major goal of the project was to catch a flare in the act, mapping all the solar high jinks associated with it from beginning to end. The sun's timing could not have been better. During the first week of observations, it set off several large flares and ejected billions of tons of matter in a prominence that extended more than 200,000 miles into space. The intense solar observations should provide clues to many of the still unanswered or only partly resolved questions about the sun: Does the solar cycle affect terrestrial weather? What internal mechanisms control the cycle? Is the sun growing cooler? Hotter? Is there a basic flaw in the current theory about the fusion process that powers the solar furnace? While the recent flares did not measure up to the March conflagration, astronomers were jubilant. "We have been exceptionally lucky," says Alan Kiplinger, a solar physicist at the University of Colorado. "It's unusual to have the sun cooperate." Fortunately for earth dwellers, the March flare occurred on the easternmost edge of the sun and thus aimed its full force away from the earth. But on March 10, when the sun's stately rotation brought the turbulent group of sunspots to a position more directly facing the earth, a second, only slightly less powerful flare erupted in the region. Eight minutes later, traveling at the speed of light, a blast of X-ray and ultraviolet radiation seared the earth's upper atmosphere. Within an hour, high-energy protons began to arrive, followed in three days by a massive bombardment of lower-energy protons and electrons. Among the first to feel the effects of the flare's fury was the orbiting Solar Max. As the radiation saturated Solar Max's instruments, a NASA spokesman reported, "the satellite was stunned for a minute and then recovered." Heated by the incoming blast of radiation, the upper fringe of the atmosphere expanded farther into space. Low-orbiting satellites, encountering that fringe and running into increasing drag, slowed and dropped into still lower orbits. A secret Defense Department satellite began a premature and fatal tumble, and the tracking system that keeps exact tabs on some 19,000 objects in earth orbit briefly lost track of 11,000 of them. Solar Max descended by as much as half a mile in a single day, almost certainly hastening its demise. On the earth, the flare's effects were equally disruptive. Shortwave transmissions were interrupted, some for as long as 24 hours, and satellite communication and a Coast Guard loran navigation system were temporarily overwhelmed. Powerful transient magnetic fields, generated in the upper atmosphere by the flare, induced electrical currents in transmission lines and wiring, and mystified homeowners reported automatic garage doors opening and closing on their own. A surge of flare-induced current was blamed by Hydro-Quebec officials for shutting down the power company's system and blacking out parts of Montreal and the province of Quebec for as long as nine hours. These startling phenomena were shrugged off by Sacramento Peak's Neidig. "A really big flare," he says, "can produce enough energy to supply a major city with electricity for 200 million years." By far the most dramatic manifestation of the solar flare was the two-night, spectacular display of the aurora borealis, or northern lights, that awed Paul Avellar and millions of others. Arriving high-energy electrons, deflected by the earth's magnetic field, spilled into the upper atmosphere near the north and south polar regions, which are unprotected by magnetic-field lines. Acting much as does the electrical current in a neon sign, the electrons banged into oxygen atoms, causing them to emit red and green light. Ordinarily far less intense and visible only in arctic climes, the glowing, flickering aurora was seen as far south as Brownsville, Texas, and Key West, Fla. Alarmed Floridians, unfamiliar with the lights and fearing that a catastrophe had occurred somewhere in the north, flooded police switchboards with calls. The two great flares of March were not isolated events. Nine other major outbursts and hundreds of smaller ones were recorded during the two weeks it took for the sunspot region to rotate out of view. In the months since, as the sun moves erratically toward its maximum, several flares have been observed every day. The sun has long been pre-eminent in human thoughts and actions. Almost from the beginning, people worshiped the sun as the beneficent provider of light and life, and as a god, called Ra by the Egyptians, Helios by the Greeks and Sol by the Romans. To the Aztecs, the sun god was Huitzilopochtli, whom they nourished with human sacrifices. Egypt's great pyramids at Giza were built with their sides aligned with the rising sun at the vernal equinox, and the temple complex at Karnak was dedicated to Ra. The ancient circle at Stonehenge, in England, was apparently constructed so that the sun would rise over one of the great stones at the time of the summ-er solstice. From the beginnings of history and literature, human beings have also invoked the sun. In rejecting peace offers from Darius before the battle of Gaugamela, Alexander the Great explained, "Heaven cannot brook two suns, nor earth two masters." And in 1911, Kaiser Wilhelm II of Germany, speaking of his nation, declared, "No one can dispute with us the place in the sun that is our due." Through the centuries, few natural phenomena have inspired as much fear and awe as solar eclipses. The ancient Chinese used firecrackers and gongs to drive away the spirit they thought was devouring the sun. Mark Twain's Connecticut Yankee, aware that a most timely total eclipse was going to occur, escaped being burned at the stake by King Arthur's knights when he predicted that the sun would disappear. A benign form of sun worship continues to this day, not only among beachgoers but also by a group of intrepid American astronomy buffs who have traveled around the world by plane, ship and jeep, from Java to Siberia to Africa, to view each of the past dozen total eclipses. Even in ancient times, however, an occasional hardy soul refused to deify the sun. The Greek philosopher Anaxagoras brazenly claimed that it was merely a ball of fiery stone, and was arrested and banished from Athens for his blasphemy. But his radical concept caught on and was later refined by Aristotle, who proclaimed the sun an unchanging sphere of pure fire, devoid of any imperfections. Aristotle's view prevailed through the Middle Ages, was embraced by Christianity and went largely unquestioned until Galileo and other early 17th century sky watchers pointed the newly invented telescope at the sun and saw black spots on its surface. So much for solar purity. Despite clerical disapproval, the reality of sunspots was quickly accepted. Still, more than two centuries passed before Samuel Heinrich Schwabe, a German apothecary and amateur astronomer, discovered the strange, cyclic behavior of the solar blemishes. Schwabe had been searching for the hypothetical planet Vulcan, supposedly the closest one to the sun, hoping to spot it in silhouette as it moved across the solar disk. In the process, he observed and kept meticulous records of sunspots over a 17-year period. Finally, in 1843, he recognized and announced the eleven-year cyclic nature of the spots and wrote, "I may compare myself to Saul, who went to seek his father's ass and found a Kingdom." In the years since, by tabulating sunspot records going back to the early 18th century and using improved telescopes, satellites, advanced instruments and modern theory, scientists have become ever more familiar with the bizarre dance of the sunspots. Each cycle begins when spots show up in both the northern and southern hemispheres about 35 degrees away from the solar equator. As the cycle matures and the older sunspots fade away (some last only a few hours, others for weeks and even months), new and more numerous spots appear at lower latitudes. Toward the end of the cycle, diminished in number, they appear at latitudes some 5 degrees from the equator. Sunspots tend to travel in pairs or groups of opposite polarity, like the ends of horseshoe magnets poking through the solar surface. During one eleven-year cycle, as the blemishes traverse the face of the sun in an east-west direction, the leading spots of each group in the northern hemisphere will generally have positive polarity, the trailing spots negative. In the southern hemisphere, the leading spots will be negative. During the next cycle, the hemisphere polarities will reverse. On average, then, 22 years will pass between solar maximums of the same sunspot polarity. This suggests to many astronomers that the fundamental solar cycle is 22 years rather than eleven. Since the sun in myriad ways governs the very existence of all terrestrial life, the cyclic changes in the sunspot population have, ever since Schwabe, inspired speculation about their effect on solar radiation and, consequently, on the earth. Though the sun is a rather ordinary star, its vital statistics are breathtaking by earthly standards. Some 865,000 miles in diameter, it consists largely of hydrogen (72%) and helium (27%) and is 333,000 times as massive as the earth. Solar temperatures range from about 27 million degrees F (if current theory is correct. But only about a third the number of neutrinos [particles with little or no mass that travel at the speed of light] that the sun should be producing at this temperature have been detected, leading some scientists to speculate that the core temperature is lower.) in the core, where 600 million tons of hydrogen are fused into helium every second, to 10,000 degrees F on the photosphere, or surface. --J. Madeleine Nash/Sunspot </body></article> </text>