Death from the Skies! (8 page)

The energy of a CME goes more into accelerating particles than it does into giving off light, so the event is actually difficult to detect initially. In fact, while the first flare was seen almost two hundred years ago, CMEs weren’t first seen until the 1970s!

However, their effect is profound. Unlike flares, which are basically a local disturbance, CMEs involve a gigantic area of the Sun. If flares are like tornadoes—local, intense, brief, and focused—CMEs are solar hurricanes. The effect is not as intense, but much, much larger: as much as
a hundred billion tons
of matter are hurled into space at a million miles per hour, and that can do far more damage on a far bigger scale.

As the CME expands off the surface of the Sun, it thunders across interplanetary space and expands to tens of millions of miles across. It creates a vast shock wave as it crosses the thin material previously ejected in the solar wind. It’s an interplanetary sonic boom, and it can accelerate subatomic particles to extremely high energy. These particles can gain so much speed that they move at a substantial fraction of the speed of light. It’s like a vast tsunami unleashed from the Sun, and it marches outward . . . sometimes toward us.

Once the CME erupts, it can cover the distance from the Sun to the Earth in one to four days. That’s all the warning we get.

It’s possible to see the actual event when it occurs. When you try to look at an airplane flying near the Sun, what do you do? You put up your hand to block the Sun, allowing you to see the plane. Astronomers do the same thing. They equip sunward-pointing telescopes with coronagraphs—generally very simple masks of metal that block the fierce light coming from the Sun’s surface—that allow fainter objects nearby to be seen. When a CME occurs, it can be seen by these telescopes as an expanding puff of light coming out from the Sun. If a CME is seen coming from the side of the Sun, astronomers breathe a sigh of relief: it will miss the Earth because it was aimed sufficiently far away from us. But sometimes the Sun is not so agreeable, and it sends a hundred billion tons of million-degree plasma screaming our way. This is seen as an expanding halo of light, because we are looking down the throat of an advancing front of subatomic particles accelerated to mad speeds.

 

When it gets here, all hell can break loose.

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.

 

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 NO
₂
, 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.