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MIT Physics 8.02 - Electricity & Magnetism

SECTION : Magnetostatics       

SUBJECT: The Magnetosphere of the Earth  

The earth sits in the magnetic field of the solar wind, which drags out the magnetic field of the sun to the neighborhood of the earth. The magnetic field lines in the polar regions of the earth connect to the interplanetary magnetic field lines, which are being carried past the earth away from the sun at high speeds by the solar wind. When the interplanetary magnetic field is southward (as is the case here) it can connect easily to the earth's magnetic field, which emerges from the south geographic pole of the earth. Energy from the solar wind flow then goes into stretching the reconnected field lines into the "magnetic tail" of the earth. Eventually those field lines "break" and snap back toward the earth on the nightside. It is this process transferring solar wind energy into magnetic energy and thence into energy flowing into the earth's atmosphere as the magnetic field lines "snap" that drives the aurora. The aurora occur at the feet of the "last closed field line", which defines the auroral oval.




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