The Spinning Magnet

by Alanna Mitchell

  So, no dynamo, no solution to the Reynolds number to describe the turbulence of the core, no ability to predict what the magnetic field will do, no way to say whether the field is in the process of reversing or, if it is, when it will happen. In fact, no precise idea of what the field looked like during past reversals and no certainty that the dynamo is operating the same way now as it has over the past billions of years it has existed.

  And without predictions, Lathrop said, we can’t prepare. Maybe we don’t need to prepare, he mused. But it would be good to know for sure.

  Prepare for what? Between Lathrop, Finlay, Constable, and others, there’s quite a list. The concern is what happens as the field is in the process of reversing. That’s when the field protecting the Earth dies down to perhaps only one-tenth of its normal strength. The magnetosphere, that stretchy web of invisible lines surrounding the Earth that makes our planet a galactic sanctuary from radiation, could show up in a more complicated pattern, Lathrop said. What will it look like when the dipole is beaten back so far that other magnetic poles are present? What will its protective force look like then?

  While Constable scoffed at the idea that a reversal is imminently on the way, she also said she is far from sanguine. The field is demonstrably not stable. She pointed to the paleomagnetic evidence that we have been living in an unusually strong magnetic field for the past few hundred years, exactly at the same time as we have developed electromagnetic systems of technology and become dependent on them. When the field weakens and solar radiation penetrates closer to the surface of the Earth, those systems could be vulnerable to attack. That’s even without a reversal. When she looks back into the archive of the past seven thousand years, she sees fluctuations that have been large enough to have serious repercussions for society.

  As for Finlay, he said he didn’t lie awake at night tossing and turning about fallout from the decaying dipole. In fact, he abhorred the alarmism that sometimes accompanied media discussions of a flip of the poles. His best analysis was that a reversal would be a leisurely process taking many hundreds or a few thousand years. Like Constable, his most immediate concern is how a weakened field will affect technology. He pointed out that the last time the field reversed, an advanced society based on electromagnetic systems wasn’t around. If the field continues to weaken, society is going to have to think about how to modify technology to protect it from surges of solar radiation. When? He gave a scientist’s answer: We would be wise to start preparing as soon as possible.

  PART IV

  switch

  [A scientist] has to have the imagination to think of something that has never been seen before, never been heard of before. At the same time the thoughts are restricted in a strait jacket, so to speak, limited by the conditions that come from our knowledge of the way nature really is.

  —Richard Feynman, Lectures on Physics, early 1960s

  CHAPTER 25

  looking up

  Boulder, Colorado, lies at the seam between the prairies and the Rocky Mountains, where the clouds, if there are any, cast sharp shadows on the land. The day I traveled there to meet Daniel N. Baker, it was hot and the flattened faces of the mountains—called flatirons, as if they could be cajoled into pressing giant shirts—stood stark against the sky. I could still see a faint sliver of moon at midday. Underfoot, as I navigated the sprawling campus of the University of Colorado at Boulder, the smell of low-slung hedge cedar rose up, mixed with the fleeting scent of spring’s first lilacs. It had been fourteen months since I had wandered the ancient streets of Clermont-Ferrand with Jacques Kornprobst, and I was nearing the end of my research.

  Like Brunhes with his fin-de-siècle observatory that reached up from the Puy de Dôme volcano, the founders of the High Altitude Observatory in Boulder were drawn to the peaks. As the space age roared ahead in the decades after the Second World War, the Boulder observatory drew academia, research, and industry together in this picturesque mountain enclave of a hundred thousand, building what had been a scientific backwater into an international power base for parsing how outer space affects humanity.

  Baker was one of the scientists who came here for what the mountains and the sky could tell him. The stars. The planets. A desire to understand an eclipse of the sun led him, as an undergraduate student in the 1960s, to the University of Iowa to study with James Van Allen. In 1958 Van Allen, then the world’s most famous astrophysicist, had discovered banks of radiation trapped by the Earth’s magnetic field in two fat crescents straddling the Earth’s magnetic equator. They’re known as the Van Allen belts and are highly stable, reliably storing radiation for long periods so that it isn’t let loose closer to our planet’s surface. Most of the radiation is charged electrons and protons created by cosmic rays crashing into atoms in the upper atmosphere and tearing them apart. The discovery of the belts marked the beginning of the space age. It founded the formal scientific study of the Earth’s magnetosphere, which is the space component of its magnetic field. It also put Van Allen on the cover of Time magazine. Twice.

  In his sophomore year, Baker took a course in modern physics from Van Allen. Van Allen offered him a job. Baker has been involved in space exploration ever since, often as a collaborator with his mentor. In 1994, after a stint at NASA, Baker became the director of the Laboratory for Atmospheric and Space Physics (LASP) at UC Boulder. His curriculum vitae runs to more than 130 pages and, by 2017, included more than nine hundred published papers—a towering scholastic output sustained over more than four decades. The odd thing about it to a science journalist is that Baker’s writing style is so plainspoken, even chatty, that you can pick up one of these papers and unmistakably hear his voice in it. Most scientific writing is far more anonymous.

  Baker lit up when he talked about Van Allen, who died in 2006, just short of his ninety-second birthday. So famous, he told me, yet so disarming. Reporters used to mob him wherever he went. Everybody wanted to talk with the great Dr. Van Allen. They would ask him: What are the Van Allen belts good for? He would answer: To hold up Van Allen’s pants! When Van Allen turned ninety, his family and friends threw him a big party back in Iowa City and invited Baker, the star student, to give an after-dinner address to the hundreds gathered. Baker put together a funny faux-Letterman top-ten list. A few weeks later he got a stern letter from Van Allen. Ever the teacher, he quibbled with some of Baker’s analysis, he told me, smiling fondly.

  Baker’s focus is how the sun’s radiation affects the Earth. The two bodies have a complicated, interlocked relationship, mediated by the elastic magnetic fields of each. By radiation, he doesn’t mean the long, slow, benign waves of heat, light, and color, but the dangerous, invisible facets of the electromagnetic field: the very short, high-frequency waves with enough energy to harm an atom or cell, such as X-rays and gamma rays. “Part of my job is to make the invisible visible,” he confided. “I see things in wavelengths most people are not sensitive to.”

  This is called ionizing radiation because it is powerful and swift enough to knock electrons out of their orbitals, creating ions, a term Faraday coined. (An ion is an atom or molecule that has a different number of electrons than protons, making it electrically charged. That lack of electrical balance makes it eager to restore its own balance, meaning it is apt to interact with another atom or molecule.) This stuff is bad for life on Earth.

  Baker is particularly interested in a different form of the sun’s energy that is not part of the electromagnetic field: highly damaging solar energetic particles. The sun is too hot for atoms to survive, even as gas, so it is mainly made of plasma, the fourth and hottest state of matter, after gases, liquids, and solids. The sun’s plasma is essentially the components of hydrogen and helium atoms. It’s electrically charged moving particles: protons, electrons, and ionized nuclei. As they move, they make electric currents and therefore a magnetic field. The sun’s plasma is so hot that some of its most energetic particles routinely break free from the g
ravitational pull of the sun and fly into space. That’s called solar wind, and it’s the force that crushes up against the side of the Earth’s magnetosphere facing the sun. Occasionally, high-speed streams of solar plasma break through holes in the sun’s outer atmosphere, or corona, and pummel the Earth for hours or days.

  The sun’s interior is restless and volatile. Its continual contortions stretch its magnetic field until, suddenly, the field lines snap back into place, releasing enormous amounts of magnetic energy. Sometimes, that shows up as a flare on the corona, a burst of electromagnetic waves of all lengths, including the longer radio waves, which can last from several seconds to several hours. Some of those waves are visible as white shapes during a solar flare. The waves travel to the Earth’s upper atmosphere in eight minutes and, if they’re strong enough, can disrupt radio transmissions.

  But solar magnetic disturbances are also capable of producing explosions of part of the corona: violent, targeted, billion-tonne masses of magnetized plasma moving at 3,000 kilometers a second or more toward the Earth. They call them coronal mass ejections. NASA has produced images of these ejections, and they look like the hot red flame from a dragon’s maw roaring toward an Earth the size of a flea. Coronal mass ejections can also produce shock waves. When the magnetic field of the ejection runs opposite to the direction of the Earth’s, it can trigger storms in the Earth’s field. One manifestation of these geomagnetic storms is auroras, like the curtains of green light I saw pulsating in the night sky above King William Island in the Arctic. Solar flares and the shock waves from coronal mass ejections can also produce solar energetic particles. That’s even faster and far more damaging radiation.

  Like solar plasma, solar energetic particle radiation is made up of protons, electrons, and high-energy nuclei. They are electrically charged and moving, which means they make electrical currents and therefore magnetic fields. They are also ionizing. Ionizing radiation—whether solar energetic particles or electromagnetic—is like an invisible bullet of energy. It can obliterate whole swaths of DNA as it passes through tissue. It can cause cancer, genetic defects, radiation sickness, and death. And in addition to episodes of solar radiation the Earth is continually attacked by galactic cosmic rays, which come from outside our own solar system, possibly from the explosion of supernovas in our galaxy, the Milky Way.

  Our protection from all this damaging ionizing radiation comes from the magnetosphere, the atmosphere, and the two Van Allen belts. And those, in turn, depend on the dynamo in the core of our planet. Early in its life, our sister planet, Mars, had an ancient internal dynamo churning out a protective magnetic shield that also episodically switched direction. That shield allowed it to have a thick atmosphere and bodies of water on its surface. By about 4 billion years ago, the dynamo died. A leading theory is that its metallic core cooled down so much that the all-important heat convection needed to make electrical currents stopped. Or the culprit could be that its tectonic plates fused—assuming it had them—making the “stagnant lid” crust the planet has now. That would mean that Mars wasn’t able to shed heat effectively from the core. Again, convection would cease. The third hypothesis is simply that the dynamo ran its course after the core shed enough heat, solidified, and resulted in an outer molten core too insubstantial to sustain electrical currents. And while the reason for the dynamo’s death is still being investigated, NASA’s recent MAVEN (Mars Atmosphere and Volatile EvolutioN) mission to Mars, which Baker was involved in, confirms the upshot: As the dynamo waned, the sun’s ferocious stream of wind and ultraviolet radiation scoured away Mars’s atmosphere. Without an atmosphere, including enough carbon dioxide gas, the planet isn’t expected to support life. It is now too cold and too vulnerable to all that radiation, but missions continue to search for evidence of it.

  NASA’s Juno mission to Jupiter, launched in 2011, which Baker is also involved in, is investigating that planet’s powerful magnetic field and radiation belts for more clues about how all the solar system’s dynamos work. Close-ups, relayed in 2017, are haunting. Looking at Jupiter’s south pole is like looking into the core of a swirled blue marble, gigantic cyclones peppering its inner reaches. More of Lathrop’s turbulence, but on a far vaster scale. Fascinating, but humbling too, to catch a glimpse of such a powerful magnetic field. Jupiter’s is about ten times as strong as Earth’s, driven by a dynamo likely nestled in a metallic hydrogen core. All this new information is helping dynamo theorists, who once only had Earth’s field to examine, realize how complex any dynamo is, Baker said.

  But to Baker, looking up also means looking forward. He has been on a long-standing quest to better predict solar storms, urging society to learn how to protect itself against these events. That led him to train his attention on the game plan of the Earth’s magnetic poles. What will happen when the poles switch places and the magnetosphere ebbs, along with the magnetic field? The very structure of the Van Allen belts, which depends on the terrestrial dipole, will be deformed. During a reversal, the belts are expected to become more complicated banded structures, far less stable, less well defined, and much less efficient at trapping radiation.

  In addition, the Earth’s field itself will not be strong enough to defend us from as much radiation, in the form of solar wind, solar flares, coronal mass ejections, solar energetic particles, and galactic cosmic rays. And the lack of protection would likely be at least a centuries-long, global phenomenon. Maybe millennia-long. Not an earthquake or tsunami or volcano that comes, wreaks destruction, and then leaves people to heal and rebuild. It would inflict damage across generations. To a scientist who has spent a lifetime immersed in the precise and peculiar possibilities of harm from cosmic radiation, this picture, which has been sharpening over the past couple of decades, presented a very large red flag.

  Baker and I had spoken at length by phone about the possible reversal of the poles, and I was in Boulder to meet with him in person. An early riser, Baker was often at his desk hours before any of his five hundred employees parked in the laboratory’s expansive parking lots. Not only is he the head of LASP, but he is a faculty member in both the physics and astrophysical and planetary sciences departments. When I met with him, LASP, which designs, builds, and tests space hardware for space missions, was operating four missions for NASA. His organization has between fifty and sixty grad students at any moment. I had been prepared to encounter a tightly scheduled chief executive. He was the opposite. He wanted to talk. He was worried.

  He ticked off the reasons. A space physicist, he had been monitoring the growth of the South Atlantic Anomaly, just as geophysicists had, but using data from NASA’s SAMPEX (Solar Anomalous and Magnetospheric Particle EXplorer) spacecraft. Rather than measuring the magnetic field itself, it measured concentrations of charged and energetic particles several hundred kilometers above the Earth’s surface—in other words, what the depression in the field let in. The spacecraft found not only that the anomaly has moved over the course of twenty years—it lies squarely over Brazil at the moment—but also that it is growing and that the field above it is weakening, a match for the calculations geophysicists are making with the Swarm satellites. Not only that, but the magnetic north pole is moving fast and the field as a whole is weakening. The kicker for Baker was that you can measure the change within the twenty-year lifetime of a spacecraft, not in the leisurely time frame of many thousands of years that the geological record normally trades in.

  So, unlike so many of the geophysicists who are carefully assessing whether the poles will flip, Baker leapt ahead to what he called “plausible scenarios.” If this is the beginning of a reversal of the poles—or even if it might be—he was compelled to consider the implications. It was his training. What would our world look like right now if the magnetic field dwindled to just one-tenth of its strength?

  As the late physicist Richard Feynman said, scientists are bound by what is known. Humans were not around during the last reversal 780,000 years ago. There are
no written or oral records to consult. Nevertheless, the past has left a few clues about what has happened during previous reversals. And scientists have seeded indications in a few other studies about what could happen, if you extrapolate. By poring through the scientific evidence for these clues, looking at the evidence of how solar storms already affect our world, and then applying those lessons to the future, we can catch a glimpse of what might come. It’s like following a trail of breadcrumbs.

  Two questions stand out. What do we know about how more intense solar weather will affect civilization? And what do we know about how it will harm living creatures, including humans?

  CHAPTER 26

  horrors the lights foretold

  The idea that damaging radiation from space can affect the Earth is not purely academic. Bursts of radiation occasionally pierce the Earth’s magnetic shield and atmosphere even now during solar storms. These unpredictable storms tend to coincide with perturbations in the sun’s own magnetic field, which peak and wane over the eleven years or so between its pole reversals. Sometimes they appear more randomly. To Daniel Baker, they provide the first pointers to what an unprotected future might look like.