Prologue Here Comes the Sun
What has been will be again,
What has been done will be done again,
There is nothing new under the Sun.
Ecclesiastes 1:9.
In March and April 2001 the Sun went boom. Or maybe it was boom, boom, boom, boom, since the Sun unleashed a machine-gun burst of explosions and space storms. The surge of solar activity made the nightly news and newspapers, complete with speculation about northern light shows and communications problems. The outburst came just as the Sun was allegedly quieting down; the peak of solar activity, or “solar maximum,” had officially arrived back in July 2000. The solar outburst in the spring of 2001 also coincided with some of the most extensive work ever performed on the International Space Station. The Sun hardly noticed man’s solar calendar.
On March 22 a large sunspot rotated around the eastern edge of the Sun and into full view from Earth (see Figure 1). Scientists labeled the area “active region 9393,” and for two weeks the group of sunspots roiled and pulsed. They swelled into a monstrosity that was visible to the naked eye at sunrise and sunset. The diameter of the active region spanned nearly 86,800 miles (140,000 kilometers), more than 22 times the diameter of Earth (see Figure 2). That same sunspot group lit up on April 2, produc
FIGURE 1. The sunspot of March 2001 was so large that it was visible with the naked eye. Note that sunspots should only be observed through special filters; otherwise, you risk blindness, as many an ancient astronomer learned the hard way. A ground-based observatory in California collected this white-light image. Courtesy of National Solar Observatory (NSO)/Association of Universities for Research in Astronomy (AURA)/National Science Foundation (NSF).
FIGURE 2. Solar active region 9393, shown here on March 30, 2001, became the largest sunspot group in a decade. The darkest structures are known as sunspot umbrae, where the magnetic fields point out vertically from the Sun; the lighter fibrous channels are called penumbrae, where the magnetic fields are horizontal to the surface. The surrounding bubble-like structures are known as photospheric granules, each of which is about 620–1,240 miles (1,000–2,000 km) across. Courtesy of NSO/AURA/NSF.
ing a rare “white-light” flare that was visible from Earth. The explosion was the most intense flare observed since scientists first began to keep records of the X-ray intensity in 1976. Scientists rated the flare an X-22 event on a scale that’s only supposed to go to X-20.
By the time region 9393 started rotating around the western limb to the back side of the Sun, another hot spot rolled into view on the eastern edge. In the first week of April, active region 9415 burst onto the scene with its own monster sunspot and its own flurry of storms. Two weeks later, region 9393 rolled back around to the front of the Sun, now named active region 9433, and bearing most of the same ugly gnarled sunspots that first appeared in
March. All told, the Sun stormed for nearly six weeks, blazing with dozens of solar flares and spitting several blobs of superheated gas, known as coronal mass ejections, or CMEs, toward Earth.
As a direct result of the storms on the Sun, a storm raged in the space around Earth and northern lights danced as far south as El Paso, Texas, and Southern California. Radio communications were distorted and occasionally blacked out over parts of the world for operators using high-frequency radio signals, such as airlines, ship-to-shore radio, and the Voice of America and BBC World Service. At least two U.S. military satellites and several commercial satellites suffered outages, hardware failures, and computer errors. Some electric power companies worked to reroute power supplies so that their equipment would not be overwhelmed by surges of electric power from space, and several transformers tripped in New York and Nova Scotia. Commercial airlines had sporadic problems with their radio signals during flights over the Pacific, and more than 25 flights between North America and Asia were diverted so as not to fly through the polar regions, where radio communication is more susceptible to blackouts and passengers are more exposed to solar radiation. The National Aeronautics and Space Administration (NASA) even considered delaying the launch of its 2001 Mars Odyssey spacecraft, which was scheduled for an April 7 liftoff. With the Sun spewing unusually high doses of radiation—particularly high-energy particles that can wreak havoc with the electronics on satellites and rocket boosters— mission controllers did not want to risk a faulty signal or computer error that could have foiled yet another Mars mission. The Sun eventually cooled off enough for the launch to take place, but not without a few days of contingency planning and heartburn.
In the midst of all of this solar storming, NASA and Russia were welcoming the second astronaut crew to International Space Station Alpha and preparing to launch another space shuttle mission to continue construction. The crew of Expedition Two—Yury Usachev, James Voss, and Susan Helms—arrived at the station on March 9, and two weeks later, active region 9393 began storming. When active region 9415 took over the fireworks, it launched an
intense solar flare and coronal mass ejection on April 18, bathing the Earth in solar particles. The next day the space shuttle Endeavor lifted off for a rendezvous with the space station and a major construction project. Space shuttle mission STS-100 included two space walks. For a little more than 26 hours, the astronauts roamed outside the station and installed the Canadarm2 robotic arm and the Raffaello logistics module, a sort of space-age moving van. NASA called the mission the most intricate and advanced robotic installation and operation ever conducted in space. It also coincided with the second most active period of solar activity in the entire solar cycle.
All through the six weeks of solar storms, physicists at NASA’s Johnson Space Center kept a watchful eye on the human occupants of the space station and the shuttles. Scientists monitor the radiation doses that crews receive on every space flight, and the March and April missions demanded acute attention. NASA’s Space Radiation Analysis Group monitored the Sun and the space around Earth with extra care during the April shuttle flight because of the extravehicular activity (EVA or, more simply, a space walk). When the Sun spits a flare into space toward the Earth, the X rays and accelerated radioactive particles can arrive at Earth in no less than 10 minutes and no more than 30. That’s not a lot of time to get an astronaut into a shuttle when he or she has been walking in space. High-energy protons from a solar flare can pierce a space suit with little trouble, causing damage to human cells and tissues that could be minor or deadly.
“With current planning and flight rules, we believe the current dose of radiation to the crew inside the space station is too small to be of concern,” said Dr. Gautam Badhwar, NASA’s chief scientist for space radiation at the time. “There is a definite but very small increase in the probability of cancer induction and mortality due to the exposure. But serious attempts are made to minimize these by flight rules.” In other words, if the Sun is spewing too much harmful radiation, flight controllers can postpone space walks and keep the astronauts hunkered down in the deepest, most shielded parts of the spacecraft. But in the spring of 2001, that was not
deemed necessary because the most severe storms never coincided with activities outside the shuttle or space station.
“The one possibility for radiation sickness might be an EVA situation during a solar event, if perhaps a crew member couldn’t be brought back inside safely,” Badhwar added. In such an event, controllers would direct space-walking astronauts to hurry back inside before the solar storm arrives, but that could take more time than nature allows. No one knows for sure what would happen to an astronaut caught outside the spacecraft during a storm (because it has never happened), but the best guesses range from skin burns and cataracts to Hiroshima-like radiation sickness.
Through good luck and watchful monitoring, the astronauts were able to safely conduct their space walks as planned in April. After the flare of April 18, the Sun was relatively quiet for more than a week, allowing the space station construction crew to complete their work without delay or danger. Ironically, the crew from Endeavor delivered several science experiments to the space station designed to assess some of the problems that will be encountered on longer future missions to the Moon or Mars. Germany’s DOSMAP dosimetric mapping experiment was used to delineate the types and intensities of radiation that seep into the space station, while Japan’s Bonner Ball neutron detector measured the number of uncharged atomic particles reaching the inside of the station. Energetic neutrons can penetrate human tissues and can affect the development of bone marrow, leading to blood diseases and cancers.
Gautam Badhwar had an experiment included in that care package from Earth. The “Phantom Torso” experiment was a mock-up of a human body that was similar to the dummies used by radiologists as they are trained to use X rays on Earth. The phantom—named Fred—was designed to replicate the head and upper-body anatomy of an adult male. The 3-foot, 95-pound model was composed of artificial human bones and skin, and organs—brain, thyroid, heart, lungs, stomach, and colon—made to closely match the density of real organs. Each of the 35 sections of the torso and each organ included radiation detectors, allowing
Badhwar and colleagues to monitor radiation doses in real time during the flight and long after the experiment was over. Phantom Fred was the first experiment to measure doses of radiation and the effects inside the human body, particularly the blood-forming organs. In the past, human radiation experiments in space (on Mir and on shuttle flights) have observed the amount of radiation that reaches the skin and then extrapolated those numbers to project the amount that reached the organs. The hope is that scientists will finally get a somewhat realistic picture of how much space radiation seeps into the body during space flights, a picture that heretofore could only be guessed at.
Two hundred years ago, before telegraphs and telephones, before rockets and radio, very few people were affected by space weather. As journalist John Brooks wrote in The New Yorker after a famous storm in 1958: “Down through the ages, [magnetic storms] no doubt raged over the Earth at intervals, confusing mariners by causing compass needles to waver, but otherwise spending their force on a planet too electromagnetically innocent to suffer from them.” Solar activity and the resulting changes in the environment of Earth were scientific curiosities, engaging mysteries for the men and women who observed the stars, navigated ships, or studied magnetism.
But then we started to harness the power of electromagnetism. We developed electric power and communications systems and built worldwide networks that are now critical for our civilization but also vulnerable to space weather. We put ourselves in harm’s way, yet very few people even know there is a problem.
In order to understand and appreciate space weather, we need to grasp three basic concepts that are mostly left out of our science books and classes. First, the Sun is a dynamic, variable star. It may seem like old reliable, barely changing from sunrise to sunset, from year to year. But when we look at it closely, with the tools of science, we see that the Sun is constantly changing, with patterns
ranging from seconds to centuries. In addition, Earth resides within the atmosphere of that Sun. Stretching well beyond Pluto and the outermost rocks and ice balls of our solar system, the atmosphere of the Sun swirls around all of the planets, carrying the imprint of its energy and magnetism in a solar wind and in the periodic explosions such as flares and coronal mass ejections. Finally, Earth responds to this changing Sun and its turbulent atmosphere. Activity on the Sun shapes, distorts, and influences the environment around the Earth. Our planet is a giant magnet, and that invisible magnetic force (the force that makes a compass needle point north) shelters us from many of the Sun’s most harmful effects. But once we start working in space, when we launch satellites and start walking in space, we move closer to the source of space weather, closer to the eye of the storm from the Sun.
Space weather is a natural hazard, one that matters to anyone who works in space or uses space to work. By using technology based on electromagnetism to communicate, navigate, predict the weather, study our environment, and defend our nations, we also have created new vulnerabilities. Every benefit must have its cost, so every tool or gadget that relies on radio waves, conducting wires, and sensitive transistors and microchips can be affected by electromagnetic disturbances in the Sun-Earth system. Space weather distorts radio and television signals as they bounce around the atmosphere. Magnetic storms can add unwanted electricity into our power lines and pipelines, causing blackouts and brownouts and fuel leaks. And because these storms can damage spacecraft, things that we now take for granted—like the Global Positioning System or our worldwide communications systems—can suddenly stop working.
An environment of which most of us are not even aware affects our economies and daily lives. We are increasingly dependent on space-based infrastructure for the humdrum things of daily life. When we watch a sitcom or sporting event on TV, when we wait by the phone for the pediatrician to answer her page, when we navigate a ship through a narrow channel or land an airplane in low visibility, when we flash a speed-payment pass at the gasoline
pump, more likely than not we are relying on space-based technology. Yet space is a place where in the blink of an eye a maelstrom can erupt, with potentially severe consequences for those technologies. Our modern electronic society is fragile, as we discovered several times in the 1990s. We are exposed and vulnerable to the whims of a star that so far defies prediction.
So it is to the citizen of the twenty-first century to whom this book is addressed. We are now a space-faring race, and we have moved beyond simple voyages of discovery. We have gone to work in space, and in time the notion of space weather will become commonplace, perhaps a feature of the nightly weather reports. We are living with a star, and if you like your electronic toys and tools—or if you work for or invest in the companies that make them—you ought to learn something more about your nearest star. The Sun is the only star we can study up close, and it is probably the only one that will affect you in your lifetime.
