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Auroras and the mysterious Sun-Earth connection

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Now, the Earth's magnetosphere and the solar wind are constantly involved in a complex dance of give-and-take. When the solar wind is particularly strong, the front of the magnetosphere is buffeted by the strength of the wind and compressed down toward the Earth's surface. When the solar wind is mild, the magnetosphere can relax back out into space. On the night side of Earth (opposite the Sun), the solar wind sweeps the magnetosphere out into a long tail, ending (we're not sure where) millions of miles out in space. This long magnetic tail is where scientists think the auroras really begin. A yet-to-be-understood interaction takes place between the magnetic field of the solar wind and our own magnetosphere, accelerating particles back toward the earth along the magnetic field lines.

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Since the Earth's magnetic field comes out of the poles of our planet, the solar wind particles are drawn along the field toward the poles. The high-energy particles from the Sun eventually run into the gases of our atmosphere, smacking into molecules of oxygen and nitrogen. It's actually a very similar to what happens inside a neon sign - the molecules of gas gain so much energy from the collision that they release light, producing the telltale glow of an aurora.

The color of the aurora depends both on what sort of molecule is being hit by the solar wind particles, as well as the altitude in our atmosphere where the action is taking place. And auroras are going on constantly. Sometimes the auroras are too dim for the human eye to see, sometimes they glow in invisible colors of light, like ultraviolet. But they're always there. Depending on how active the Sun is, they may be clustered right up over the magnetic pole, or spread clear across the middle latitudes, like a recent aurora that reached all the way down to northern Florida. And the Earth isn't the only planet we've seen auroras on; both Jupiter and Saturn's are bright enough to be seen by the Hubble Space Telescope.

But there's a bigger issue here besides the fascinating and lovely auroras. For years now, scientists have tried to figure how the magnetic phenomena of the Sun (like sunspots, flare, and the solar wind) truly effect the environment of the Earth. At first you wouldn't think that far-away dark spots on the Sun, or lights in the polar skies would have any noticeable effect on our climate or weather. In truth, scientists are beginning to get a little nervous about that.

There is some evidence, still preliminary, that the magnetic behavior of the Sun may have dramatic consequences for the Earth. A famous example in our history is the "mini-ice age" and the "winter without a summer," events which took place during the seventeenth century. Even with the primitive scientific apparatus of the day, scientists noted that the extreme climate changes coincided exactly with the complete disappearance of sunspots. Scientists are still trying to link climate changes on Earth to solar activity. Sometime tantalizing correlations are seen, but other times the opposite seems to be true. The complex magnetic interactions of the Sun and Earth, and the energy they impart to our environment, are still beyond our understanding.

But one thing seems certain: a connection is there. It may end up being insignificant, or it may end up helping up predict dramatic changes in our weather and climate. Regardless, the Sun and Earth are a single unit, to some degree. So, if you have the chance on a cold winter night, go outside and watch the sky as far-flung bits of the Sun dance away in our upper atmosphere. And the Sun-Earth connection can be a personal one too.

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