The Cusp
The Cusp

The cusp is a funnel down which magnetosheath particles entering the outer magnetosphere precipitate to the earth. The particles precipitate along magnetic field lines. If there were no solar wind then the earth's outermost magnetic field lines would converge on the magnetic pole. When the solar wind blows, it gathers up the earth's magnetic field into the magnetosphere whose outermost magnetic field lines now converge on an area close to, but sunward of, the magnetic pole on the earth.

Interball Polar DE

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