A perturbation theory analogous to that of quasi-linear theory is developed to treat the behavior of magnetic surfaces, in particular to estimate their stability against field irregularities. The method exploits the similarity between the Vlasov equation and the Liouville equation for field lines. We find that a very important role is played by field resonances, that isolated resonances have a limited effect, extended over a finite width which we estimate, but as soon as resonances overlap, a very rapid destruction of flux surfaces may be expected.
準線形理論と類似の摂動理論を、磁気面の挙動、特に磁場の不規則性に対するそれらの安定性を評価するために展開する。この方法は、ブラソフ方程式と磁力線に対するリウヴィル方程式との間の類似性を利用する。磁場共鳴が非常に重要な役割を果たすこと、孤立した共鳴は限られた効果しか持たず、その効果は我々が評価する有限の幅に及ぶが、共鳴が重なり合うとすぐに磁束面の非常に急速な破壊が起こり得ることが分かる。