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Big enopugh to engulf 1,300,000 earths, the sun is obviously the biggest thing in the solar system. When we look at the sun it doesn't appear so big, though, obviously it is extremely far away from us. So how do we know that the sun is made of ionized gas, or plasma? By studying the light emitted by the sun, scientists can gain information about an object's heating, chemical and atomic conditions. The sun turns out to have a temperature of 10,300 degrees fahrenheit at the surface, and is predicted to be between 25-35 million degrees fahrenheit at the center. At these kinds of temperatures it HAS to be made up of plasma. No form of other matter could exist under these extreme conditions, even with the type of pressure exerted on the ions at the center. The kinetic energy is just too great. The sun, just like the earth, has both a north pole and south pole which form its magnetic field. This magnetic field is the source for the lines of force which the plasma then revolves around. Unfortunately, the sun's magnetic field is not yet completely understood, in fact, we've barely scratched the surface. What we do know, though, is a little something about the corona. The sun's corona, which is only visible during a solar eclipse, is composed of pure plasma. Of course, as the corona reaches further and further out into the reaches of space, the density becomes much less. It has been proven that the corona probably extends out to engulf our earth and all the other planets, except for maybe those at the far edge of the solar system. In fact, the seemingly empty space around the earth is filled with a swirling solar wind made up of ionized gas particles shot out from the sun. This solar wind is not like the wind we experience, though. First of all it is very thin. Near the sun the density amounts to about 100 million particles per cubic centimeter, still far below the density of the earth's atmosphere. By the time it gets to earth the density drops to about 50 particles. Second, it has a much greater temperature, meaning the particles move at much greater speeds and have larger kinetic energy. Strangely enough, this results because of the corona being so hot. It's actually hotter than than the surface of the sun, one million degrees fahrenheit compared to 10,300 degrees. How is this possible?
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Plasma acts like a wave, much like the electron does. It can transmit and carry many different kinds of waves, including sound waves. Sound waves are a very convenient way of transmitting energy since they can pass through gas without greatly heating it. Although it is a molecular motion, it is one that leaves the molecules at the same relative speed that they started off with. A particle gets the push, but then loses that extra energy as it passes it on the next particle. Now, when on the surface of the constantly bubbling sun a upwelling current of hot gas explodes outward, it produces giant roars of sound which carry the heat energy from the center of the sun out past the surface and a bit of the way into the corona. Because the density of particles in space becomes too small, another wave has to take over since sound waves are no longer efficient. This next wave is passed along by the magnetic field lines and plasma which act as a type of jelly. It is through this jelly that the heat then travels through, and ends up making the corona extremely hot.
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Near the equator of the sun there are separate magnetic fields. These fields are connected with areas of disturbance known as centers of activity(CA's). These CA's are embedded below the surface and have their own magnetic fields. This field is the cause of many features of the CA, including the sunspot. The reason for sunspots lies again with the properties of plasma. Since ions tend to circle around lines of force and never pass through magnetic fields straight on, the ions get stuck within the magnetic field. These "spots" continue on giving off heat, but no more energy comes into the the area in the form of hot gas currents. This causes the sunspot to cool and appears dark since it is giving off less light than the surrounding surface and provides a contrast. The CAs also cause what we know of as solar flares. Most solar flares occur after a sunspot has disappeared and release a torrent of radiation made up of intense ultraviolet light and X rays, together with very fast-moving ions and electrons. These particles are, of course, plasma. Now here's the part that affects the earth. As these flares release the plasma, it shoots out into space. Now remember that a plasma particle and magnetic field line seldom separate, and are always together. Well, as the plasma travels through space it carries the line of force with it, sometimes crossing paths with the earth. These particles carry with them enormous amounts of energy, which could allow the particle to ram through large amounts of other type of matter. In addition, barriers would not be very effective because of the way the particles move. Because they swirl about the line of force they could go around obstacles. This type of radiation is very dangerous, and luckily for us, the earth is prepared, as will be discussed later.
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