Fig. 1.

Sketch of the CSSS model. The inner black circle is the photosphere, the middle circle is the cusp surface, and the outer circle is the source surface. At the cusp surface the field lines become open and at the source surface they become radial. The field lines that remain beneath the cusp surface are closed field lines. Red lines denote away-field, blue lines towards-field, and green lines are closed.
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