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1 .Listen to part of a lecture in an Astronomy class
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2 .(male professor) The main thing to keep in mind as we study the Sun is magnetism.
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3 . The Sun’s magnetic field is produced by the flow of electrically charged particles.
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4 .And you’ve all heard of sunspots, right, those dark spots on the surface of the Sun?
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5 . OK, well, sunspots appear when very intense regions of magnetism rise to the Sun’s surface.
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6 . The locations where sunspots appear drift back and forth between the Sun’s equator and the poles.
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7 .That we’ve known about for a long time. They appear closer and closer to the Sun’s equator over the course of about an eleven-year cycle before circling back to the poles for the next eleven or so years.
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8 .And this continual movement of the location of sunspots, these shifting magnetic fields, is the cause of pretty much all solar activity, what we call solar storms, such as flares, solar wind, and so on.
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9 .And this is important to know because solar storms send radiation into space often disrupting communication systems here on Earth.
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10 . Very strong storms affect our weather satellites and even mobile phones, so it’s helpful to know when they might happen.
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11 . OK, so, sunspots are areas of concentrated magnetic fields and the movement of sunspots is directly related to the intensity of solar storms.
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12 . And just like weather on Earth, solar storms can be intense or mild depending on how much sunspot activity there is.
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13 . Well, we’ve recently discovered what causes the Sun’s magnetic fields to move and in doing so we’ve learned a way to predict the strength of solar storms.
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14 .It turns out that sunspots are moved by a giant circulation system about 200 kilometers below the Sun’s surface, a great conveyor belt as we call it.
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15 .It’s actually two belts. See here? One above the Sun’s equator and the other below.
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16 .And these conveyor belts move the sunspots in a loop, between the solar equator and the poles.
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17 . Now, remember, there’s a similar circulation system here on Earth. It’s the Great Ocean Conveyor Belt.
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18 . The great ocean conveyor belt is a network of currents that carry water from ocean to ocean and it controls the weather on Earth.
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19 .Well, in much the same way the Sun’s conveyor belt controls the weather on the Sun.
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20 .But instead of carrying water, it carries gas.
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21 .And as the belt moves, it sweeps up, it collects magnetic fields, and it affects the development of future sunspots.
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22 .Now, how do you observe a gas belt that’s 200 kilometers below the Sun’s surface?
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23 . Well, it was the movement of sunspots that led to the discovery of this belt.
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24 .By measuring the speed that sunspots drift toward the equator or poles, we get an idea of the speed of the belt.
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25 .OK, now, as I said, the average sunspot cycle is eleven years. It varies somewhat. In shorter cycles the circulation of the Sun’s conveyor belt is faster and in longer cycles it’s slower.
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26 .And we can predict the intensity of solar storms by looking at the speed of the sunspot cycle.
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27 .In other words, the circulation of the belt influences the time it takes for sunspots to drift to the equator or poles.
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28 .But it also influences the strength of future sunspot activities and the intensity of solar storms.
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29 . Let me explain. The faster the belt moves the more magnetic fields it sweeps up.
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30 .That means the number and size of the sunspots will be larger two sunspot cycles later.
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31 .An intense sunspot cycle will mean more solar storms and vice versa.
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32 .And that’s important because, well, think about the safety of space flight, for example. This next sunspot cycle is supposed to be intense. We’ve determined that from calculating the belt speed about twenty years ago.
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33 .And when solar activity is intense, it means there’ll be dangerous radiation storms in space.
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34 . In recent years, the movement of the belt has slowed down considerably, which means that about twenty years from now, there’ll be a weak sunspot cycle and we probably won’t have to worry about radiation storms. Good news for astronauts!
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35 . Now, can we use the conveyor belt to predict the solar maximum?
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36 . Uh, the solar maximum is the time of the most intense solar storms during a cycle.
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37 .That’s something we wanted to do for a long time personally, that would be nice, but, well, while the Sun’s conveyor belt does give us a solid way to predict the general intensity of solar storms, we are a long way off from more specific predictions.
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