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A different approach is offered by recognizing that the flux surfaces are topological toroids of a single parameter. | A different approach is offered by recognizing that the flux surfaces are topological toroids of a single parameter. | ||
Then, the surface area and volume corresponding to such surfaces are related via a differential equation. | Then, the surface area and volume corresponding to such surfaces are related via a differential equation (''dV = S dr''). | ||
Assuming only that ''S'' is linear in ''r''<sub>eff</sub> (or ''V'' is cuadratic in ''r''<sub>eff</sub>), it follows that: | Assuming only that ''S'' is linear in ''r''<sub>eff</sub> (or ''V'' is cuadratic in ''r''<sub>eff</sub>), it follows that | ||
''dr = (dS/S) dV/dS = dr/r dV/dS'', so: | |||
* ''r''<sub>eff</sub> = ''dV/dS'' | * ''r''<sub>eff</sub> = ''dV/dS'' | ||
This definition is more general, although its validity is subject to the mentioned assumption. A fully general definition follows from | This definition is more general, although its validity is subject to the mentioned assumption. A fully general definition follows from |