Read Online Death from the Skies! by Ph. D. Philip Plait - Free Book Online
Authors: Ph. D. Philip Plait
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atmosphere can heat up from this and “puff up” like a hot-air balloon. If the atmosphere expands enough, it can actually reach the height of some satellite orbits. A satellite normally orbiting in a near-vacuum environment may suddenly find itself experiencing drag as it plows through the very thin extended atmosphere. This lowers the satellite’s orbit, dropping it into even thicker air, where it drops more, and so on. Even if it survives the initial flare, it may still be destroyed when it burns up in the Earth’s atmosphere! Many low-orbiting satellites are lost every solar cycle because of this effect. The American space station Skylab was destroyed this way in 1979.
Because of this, space agencies and commercial satellite owners watch for flares very closely. Flares are linked to the eleven-year sunspot cycle, tending to occur on or around the solar sunspot maximum, though for reasons still not well understood, the most energetic flares usually happen about a year after maximum. Incidentally, the 1859 flare, perhaps the brightest of all time, occurred a year or so before the sunspot maximum.
That flare induced quite a bit of magnetic activity on the Earth. While the flare itself probably did have some direct effect on the Earth, it’s now thought that it had some help.
HALO, HOW YOU DOING?
Normally, there is a relatively constant flow of material from the Sun. Called the solar wind, it’s a stream of subatomic particles accelerated by the usual suspect: the solar magnetic field. The solar wind blows off the Sun in all directions, and continues outward for billions of miles, well past the orbit of the Earth around the Sun. Near the surface of the Sun, the particles can be seen as a faint pearly glow called the corona. The corona is incredibly hot—billions of degrees—but extremely tenuous, like a laboratory-grade vacuum. But over the trillions of cubic miles of solar surface, even something so diffuse can add up to a lot of mass. Astronomers think of the corona as the atmosphere of the Sun, so, in a very real sense, we live in the atmosphere of a star.
This has some disadvantages. Atmospheres sometimes have bad weather.
When a flare erupts from the surface of the Sun, needless to say, it tends to have an effect on its environment. The blast of energy and particles from the flare goes upward, of course, away from the Sun, but it also goes downward, onto the surface. This creates a seismic wave on the surface of the Sun with tens of thousands of times the energy of the strongest terrestrial earthquakes. The Sun’s surface ripples as waves of energy are slammed into it. The magnetic field lines surrounding the energy get an enormous jolt as well, and many times this is enough to disrupt them. The lines going in and out of the Sun’s surface in the area reconnect, release energy, and disrupt more lines around them. More and more energy is released as the effect spreads and more lines reconnect.
As this occurs, the matter that was previously constrained by those magnetic fields suddenly finds itself able to expand under the intense pressure. Instead of a single coil springing open as in a flare, it’s as if they are all free to expand. The matter suddenly bursts outward in a coronal mass ejection, or CME. 13
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
Because of this, space agencies and commercial satellite owners watch for flares very closely. Flares are linked to the eleven-year sunspot cycle, tending to occur on or around the solar sunspot maximum, though for reasons still not well understood, the most energetic flares usually happen about a year after maximum. Incidentally, the 1859 flare, perhaps the brightest of all time, occurred a year or so before the sunspot maximum.
That flare induced quite a bit of magnetic activity on the Earth. While the flare itself probably did have some direct effect on the Earth, it’s now thought that it had some help.
HALO, HOW YOU DOING?
Normally, there is a relatively constant flow of material from the Sun. Called the solar wind, it’s a stream of subatomic particles accelerated by the usual suspect: the solar magnetic field. The solar wind blows off the Sun in all directions, and continues outward for billions of miles, well past the orbit of the Earth around the Sun. Near the surface of the Sun, the particles can be seen as a faint pearly glow called the corona. The corona is incredibly hot—billions of degrees—but extremely tenuous, like a laboratory-grade vacuum. But over the trillions of cubic miles of solar surface, even something so diffuse can add up to a lot of mass. Astronomers think of the corona as the atmosphere of the Sun, so, in a very real sense, we live in the atmosphere of a star.
This has some disadvantages. Atmospheres sometimes have bad weather.
When a flare erupts from the surface of the Sun, needless to say, it tends to have an effect on its environment. The blast of energy and particles from the flare goes upward, of course, away from the Sun, but it also goes downward, onto the surface. This creates a seismic wave on the surface of the Sun with tens of thousands of times the energy of the strongest terrestrial earthquakes. The Sun’s surface ripples as waves of energy are slammed into it. The magnetic field lines surrounding the energy get an enormous jolt as well, and many times this is enough to disrupt them. The lines going in and out of the Sun’s surface in the area reconnect, release energy, and disrupt more lines around them. More and more energy is released as the effect spreads and more lines reconnect.
As this occurs, the matter that was previously constrained by those magnetic fields suddenly finds itself able to expand under the intense pressure. Instead of a single coil springing open as in a flare, it’s as if they are all free to expand. The matter suddenly bursts outward in a coronal mass ejection, or CME. 13
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
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