Read Online Death from the Skies! by Ph. D. Philip Plait - Free Book Online Page A
Authors: Ph. D. Philip Plait
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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.
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
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.
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
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