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Transcript for THEMIS web short
December 16, 2008

NASA's THEMIS mission has overturned a longstanding belief about the interaction between solar particles and Earth's magnetic field.

The Earth's magnetic field is like a giant bar magnet. This magnet forms a protective field around the Earth shielding us from the solar wind that is constantly streaming towards Earth. This shield is called the magnetosphere.

"The solar wind is primarily comprised of protons and electrons. They're streaming outwards from the sun at up to a million miles per hour and they're constantly bombarding Earth's magnetic field. We're shielded by our Earth's magnetic field most of the time, however a small fraction of the solar wind particles get in to the Earth's magnetic field, are energized and become the Earth's radiation belts, which can damage spacecraft and harm astronauts."

But the sun has a magnetic field of its own as well, which the solar wind carries outwards towards Earth. And the THEMIS spacecraft fleet recently observed that twenty times more solar particles get in to the Earth's magnetosphere when the sun's magnetic field aligns with that of the Earth, than when they are pointed in opposite directions.

"In the past researchers found that the energy from the sun get in to the Earth's magnetic field at times when the Earth's magnetic field points southward. Here we found that when the particles get in the plasma, the particles from the sun get in to the Earth's magnetic field when the sun's magnetic field points northward. For a long time people have known that the location where particles and energy get in to the Earth's magnetic field depend on the orientation of the sun's magnetic field. But they just hadn't realized how many particles get in for the northward orientation of the sun."

So, what do these new finding mean for us here on Earth? Well, with this new information, scientists can make better predictions about when solar storms will be severe. Meaning we can better prepare for the power outages, satellite damage and other problems that these storms can often cause.

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