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== Flux surfaces == | == Flux surfaces == | ||
An important concept in this context is the | An important concept in this context is the [[Flux surface|flux surface]], which is a surface such that ''B'' is everywhere perpendicular to its normal. | ||
The force balance equation implies that ''p'' is constant along any field line (since ∇''p'' is perpendicular to ''B''), which is an expression of the underlying assumption that transport along the magnetic field lines is much faster than transport perpendicular to it. | The force balance equation implies that ''p'' is constant along any field line (since ∇''p'' is perpendicular to ''B''), which is an expression of the underlying assumption that transport along the magnetic field lines is much faster than transport perpendicular to it. | ||
The force balance equation also implies that the surface ''p'' = constant is a flux surface (assuming flux surfaces exist). | The force balance equation also implies that the surface ''p'' = constant is a flux surface (assuming flux surfaces exist). |