On May 13, 2005, the orbiting Solar and Heliospheric Observatory captured this image of a CME heading right for Earth at 3 million miles per hour. When the wave hit, it caused a magnetic storm that spawned aurorae seen as far south as Florida.
SOHO (ESA & NASA)
When it gets here, all hell can break loose.
RINGING THE DOORBELL
The Earth has a magnetic field that is similar in some way to the Sun’s. It’s probably generated by the motion of hot, molten rock and metal inside the Earth in a process similar to that which takes place in the Sun (with the Sun, though, the material is extremely hot gas), and is powered by a dynamo like the Sun’s field as well. This magnetic field extends past the Earth’s surface and reaches out into space, forming a region called the magnetosphere. If the Earth were alone in space, the field would surround our planet in a shape like that of a doughnut—the three-dimensional version of the crescent-shaped lines seen when you put iron filings on a piece of paper with a bar magnet under it. However, the constant stream of particles flowing past the Earth from the solar wind shapes the Earth’s magnetosphere into a teardrop shape, like water forming teardrop-shaped sand banks in a river. The pointy end always faces away from the Sun, and is called the magnetotail.
Most people are aware that the Earth’s magnetic field can be used to find north,14 but it also acts something like a protective force field, rebuffing any passing charged subatomic particle and sending it on its way. This protects us from the more severe effects of solar temper tantrums. It even protects our atmosphere: without the magnetosphere, the solar wind would have long ago eroded our air away, leaving the Earth a barren rock similar to Mercury. Mars probably lost most of its atmosphere this way as well.
So the Earth’s magnetic field is a good thing. Usually.
When a CME from the Sun reaches the Earth, it interacts with the Earth’s magnetosphere. The sheer energy of the flow can snap the Earth’s sunward-facing magnetic field lines, blowing them back around to the night side of the Earth into the magnetotail, where they can reconnect—it’s a bit like a stiff wind blowing your hair backward and making it all tangle up on the back of your head.
When the Earth’s field lines reconnect in the magnetotail, a lot of energy is released. Charged subatomic particles flow along the lines, down toward the Earth. Accelerated by the magnetic field, they slam into the Earth’s atmosphere, ionizing molecules in the air, stripping them of their electrons. When the electrons recombine with atoms, light is emitted with characteristic colors: oxygen molecules give off red light, and nitrogen green.15 Since this happens where the magnetic field lines of the Earth drop down into the atmosphere near the poles, in general people living at extreme northern and southern latitudes who venture outside during such an event are met with a brilliant display of aurorae—aurora borealis for the north, and aurora australis for the south. In a particularly powerful event, it’s possible to see them at mid-latitudes as well; the 1859 white-light solar flare event spawned a massive CME that caused aurorae to be seen as far south as Puerto Rico.
Aurorae have mesmerized people for millennia, and it was only recently understood that they are harbingers of vast unseen forces at play high above our heads, forces that trace their origins back to our nearest star and to the unimaginable violence wreaked there.
The effects of a big CME are far larger than a simple light show, however. For one, they compress the Earth’s magnetosphere. A satellite orbiting above the Earth inside the protective magnetic field may suddenly find itself exposed to the full brunt of the CME. The incoming radiation can then fry it.
The Earth is not the only planet affected by the Sun. This ultraviolet image from the Hubble Space Telescope shows an aurora at Saturn’s north and south poles. Any planet with a magnetic field can experience magnetic storms when the Sun is active.
J. T. TRAUGER (JET PROPULSION LABORATORY) AND NASA
There are even more profound effects from a big CME, ones that affect us directly, even on the surface of the Earth.
Remember that a changing magnetic field can induce a current? Well, when the magnetic field of the Earth changes rapidly because of a CME impact, any nearby conductor can suddenly find itself dealing with a huge surge of current.
There are plenty of such conductors on the surface of the Earth . . . like the entire North American power grid. Think of it: millions of miles of wires, all designed specifically to carry current from one place to another! Under normal operating conditions, these wires are easily able to carry a large amount of current, making sure that electricity generated at, say, Hoover Dam can be sent to Los Angeles to power someone’s margarita blender.
But these wires are very sensitive to solar storms. For one thing, these storms add a huge load to the system. For another, current heats up wires, causing them to sag. This process is well understood by electrical engineers and under normal operating conditions the system is designed to withstand it. However, a big pulse of current caused by a storm can add to the load already there, causing lines to heat up too much and break. For a third, over the years, more power generators have been added to the grid, but not more wires. As time has gone on, American power demands have grown. The wires were originally built to hold quite a bit of current, but in many cases they are operating closer and closer to their full capacity. A big surge can blow out the huge transformers vital to making sure the high-voltage electrical current in wires gets dropped to much lower voltages before going into your house. These transformers are expensive (some are as big as houses) and losing them can mean whole cities might go without power for great lengths of time.
Case in point: on March 6, 1989, an ugly and enormous group of sunspots rotated into view on the solar surface. Spanning 43,000 miles, they had already spawned many flares that were detected even though the spots themselves were on the far side of the Sun. Astronomers expected the worst.
They got it. Over a two-week period, Active Region 5395 blasted out nearly two hundred solar flares, a quarter of them rating in the highest energy category. At the same time, thirty-six CMEs were detected screaming out from the Sun.
Some of the effects were merely annoyances in the grand scheme of things. A microchip manufacturer had to shut down operations temporarily because some sensitive instruments were not behaving during the magnetic upheaval. Compass readings were off by many degrees, making navigation for ships difficult. Many satellites lost altitude—by as much as half a mile—and one military satellite could not compensate for the effects, and began to tumble. Other satellites were fried as well.
But the worst effects occurred on March 13, when a vast geomagnetically induced current was created by the storm. Voltage fluctuations caused power problems around the planet. In New Jersey, the current induced by forces far overhead blew out a power plant’s 500,000-volt transformer, which cost $10 million to replace. It took six weeks, and the company lost nearly twice that much money in lost power sales during that time.
In Quebec, the effect was much more serious. The current surge shut down a power generator, and the sudden loss of power collapsed the grid. Transmission wires failed over a huge area, some exploding in flames. In the middle of a winter’s night, the electricity for six million people in Canada was flicked off by the Sun. It took days to get the grid fully back up. Models of the event made by engineers estimated the total damage cost at several billion dollars.
As with asteroid impacts, there are ways to mitigate the damage done by flares and CMEs. Satellites can be designed to withstand particle and gamma-ray impacts, but at a significant cost to the manufacturer. The same is true for power grids; it would cost billions to retrofit power stations and add more power lines to accommodate another March 1989 event.16
Such events are rare, occurring two or three times per century. But as we make more demands on our power grids, the risk of potential damage from the Sun only increases.
And there is yet another direct impact from solar activity. Models of the impact of
the 1859 event on our atmosphere have shown that the subatomic particles accelerated in the Earth’s magnetosphere by the event would have cascaded down into the atmosphere, breaking up (what scientists call dissociating) molecules of ozone in the upper atmosphere. Ozone is a molecule made up of three oxygen atoms (the molecule of oxygen we breathe has two atoms bound together), and is very efficient at absorbing the Sun’s ultraviolet light, protecting us from it. The amount of ozone depletion from the 1859 flare would have been relatively modest, just a few percent. However, that is enough to allow increased UV radiation to reach the Earth’s surface. The effects of this on humans are unclear because of spotty medical records from more than a century ago, but it’s possible there was a small but significant rise in skin disease in the years following the event. This increase in UV can also affect the ecosystem and food chain (see chapter 4 for more details on that than you want to know), though again the records from that time are incomplete.
There was, however, at least one measurable effect from the 1859 event. When broken up by incoming particles, the dissociated air molecules can recombine to form other chemical compounds, including NO2, or nitrogen dioxide.17 This reddish-brown gas, created high in the atmosphere, would wash down to Earth in rain and be deposited on the ground. Studies of ice cores from Greenland have shown an increase in the deposition of nitrates from that time.
The problem is, the NO2 can oxidize in the atmosphere to form nitric acid. When this dissolves in water droplets, acid rain can result, with terrible effects on the Earth’s ecosystem. This did not appear to be a major problem from the 1859 event, but if in the future more energetic eruptions impinge on our atmosphere, we may be able to measure the effects of that as well. That’s just another fun way the Sun can slam us.
CLIMATE OF CHANGE
With all this talk of magnetic storms, flares, and CMEs damaging the Earth, are we missing something more obvious? The Sun is, after all, far and away the major source of heat in the solar system. While the Sun seems rock-solid in its energy output, we have already established that it’s a variable star. Sunspots wax and wane on an eleven-year cycle; could this possibly lead to a change in the amount of energy we receive from the Sun? And if more or less sunlight hits the Earth, could that then lead to climate change on Earth, and a potential mass extinction?
It should be noted immediately that time and again, people have tried to tie the Sun’s eleven-year cycle with events here on Earth. The stock market, baseball scores, even personality traits have been (dubiously at best) linked to sunspot numbers. The problem is, if you look at enough cycles, some are bound to line up superficially. You have to be able to separate the wheat from the chaff, which can be very difficult.
Scientists have been arguing for years over whether there is some correlation between solar activity and weather on Earth. It seems that there is, but the factors involved are subtle and difficult to pin down. If they were clear, there’d be nothing to argue over. However, there are some connections that appear to be firmly in place . . . and sunspots do play a role. But the direction of that role might surprise you.
Sunspots are dark, cooler patches of the Sun’s surface. You might think, then, that if there are lots of sunspots, we get less light and therefore less heat from the Sun. So, lots of sunspots equals cooler climates.
But spots are only dark in visible light. There are bright regions surrounding sunspots called faculae (literally, Latin for “little torches”) that form because of the complicated connection between the Sun’s surface magnetic field and the hot gas bubbling up from deeper regions. The gas in the faculae is hotter, and therefore brighter. On average, sunspots are 1 percent darker than the Sun’s surface, but faculae are 1.1 to 1.5 percent brighter. This means that when the Sun is covered in spots, it’s actually brighter in visible light than it is when there are fewer spots!
The primary source of heat for the Earth’s surface is the visible light from the Sun. Studies have shown that when the Sun is at the peak of its cycle—when sunspots and faculae are more prevalent—the overall solar irradiation of the Earth increases by just about 0.1 percent. This is a small but significant increase—it causes a global temperature increase on Earth of about 0.1 to 0.2 degree Celsius (about 0.2 to 0.4 degree Fahrenheit). The opposite is also true; during the sunspot minimum, the Earth’s average temperature decreases by a fraction of a degree.
Let’s face it: this is a pretty small effect. By itself, it hardly changes anything on Earth. However, heating of the Earth’s surface from the Sun is only one way the climate can be affected. There are lots of other sources of climate change, as we are now all too aware. In many cases, these sources by themselves don’t do much to the climate.
But what if two or more of these effects add up?
Things can get bad. We need only to look back in time a short way to see how.
The existence of sunspots had been known for centuries, even before the invention of the telescope. But once telescopes were trained on the Sun, the view naturally improved. People have been monitoring the size and number of sunspots nearly continuously since the early 1600s.
In 1887, an astronomer named Gustav Spörer noticed that the records of sunspots appeared to show an absence of spots between the years 1645 and 1715. For literally seventy years, the Sun’s face was virtually blank, clean of solar acne. In the late 1800s, the scientist E. W. Maunder summarized Spörer’s findings and published them. We now call this period of sunspot deficit the Maunder Minimum.
All of this would be somewhat academic if not for one rather critical point: the years 1645 to 1715 were also a time of much lower than average temperatures across Western Europe and North America. It was so cold that the Thames River froze over (which it generally does not do, even in winter), glaciers in the Alps advanced, destroying whole villages, and the Dutch fleet was frozen solid in its harbor. This period was called the Little Ice Age.
It’s awfully tempting to directly connect the Maunder Minimum with the Little Ice Age, but we have to be very careful. In nature, it’s rare for a single effect to have a single cause, especially when the effect is as dramatic as a prolonged climate change. Usually, there are a number of events that have to occur to manufacture such a big change.
It turns out the Little Ice Age may have started long before the Maunder Minimum, even as early as the mid-thirteenth century. Caspar Ammann, a solar physicist who has extensively studied the connection between the Sun’s output and the Earth’s climate, notes that the Little Ice Age was not one continuous event, but instead consisted of “several pulses of cooling episodes . . . the first one started in the 1250s through 1300, after a medieval warming period.” Clearly, there were other causes of the temperature drop.
The biggest culprit is probably volcanic activity. There are clear signals of eruptions during the Little Ice Age, mostly seen in ice cores: atmospheric gases trapped in polar ice can be studied to determine what was happening in the Earth’s air during certain times in history. Interestingly, in the 1690s, the Little Ice Age got very severe, especially in Western Europe—there are stories of birds literally freezing to death sitting in branches. At this very time, there is a large spike in the amount of atmospheric sulfur found in ice cores, indicating large levels of volcanic activity. Volcanoes launch sunlight-reflecting dust and gases into the air, reducing the amount of visible light reaching the Earth’s surface. This cools the planet by lowering the amount of heat the surface can absorb.
By itself, this could not cause the severest parts of the Little Ice Age. But together with the Maunder Minimum, when the global temperatures would have dropped, it could have lowered the Earth’s average temperature even more.
Still, if this were a global effect, why was Western Europe hit so much harder than everywhere else?
It turns out there is a third player in this game. This gets a little complicated, so strap yourself in.
During a sunspot minimum, there is less solar activity in general. Besides there being less vis
ible light, there is a drop in the amount of sunlight across the spectrum, including ultraviolet light. This turns out to be important: UV light is what helps create the Earth’s ozone layer; it turns normal atmospheric oxygen (O2) into ozone (O3). If there is less UV, there is less ozone. Ozone is actually quite important in the temperature balance of the upper part of the atmosphere, called the stratosphere. When there is lots of ozone the stratosphere is warm (because it absorbs UV light), and when there is less ozone the stratosphere is cooler.
Most, but not all, of the ozone creation happens in the tropics, at low latitudes near the equator. That’s because that’s the part of the Earth getting the most sunlight, and therefore the most UV. In the summer, ozone can be created both at the equator and at the pole, because that whole hemisphere is in sunlight. In that case, the difference in temperature in the stratosphere from pole to equator is minimal.
But in the winter, the pole is in darkness. No UV reaches the stratosphere, so no ozone is created there. That in turn means there is a big temperature difference in the ozone layer between the equator and the pole.
The problem is that the jet stream is sensitive to these temperature differences. In the winter, the temperature change across latitudes is large. This drives a strong jet stream, which circulates very firmly around the globe. But in the summer, when the gradient is smaller, the jet stream weakens. Instead of making a tight circle, it meanders, flopping down loosely to lower latitudes. When it does this, it can bring cold air from the Arctic to southern locations, and warm air from the south up to higher latitudes.18
As it happens, the jet stream tends to dip down more at certain locations on the Earth than others. Western Europe is one such place.
This then is the most likely scenario for the very bitter winter cold snap in the 1690s in Europe: volcanic activity dropped the global temperatures, as did the Maunder Minimum. Together they made things cold, but not brutal. But the drop in solar activity dropped the Sun’s ultraviolet output, which lowered ozone production on Earth. This changed the direction of the winter jet stream, bringing the unusually cold Arctic air down to Western Europe.
Death From the Skies!: These Are the Ways the World Will End... Page 6