http://arxiv.org/abs/2009.14048
When a magnetic field is forced to evolve on a time scale $\tau_{ev}$, as by footpoint motions driving the solar corona or non-axisymmetric instabilities in tokamaks, the magnetic field lines undergo large-scale changes in topology on a time scale approximately an order of magnitude longer than $\tau_{ev}$. But, the physics that allows such changes operates on a time scale eight or more orders of magnitude slower. An analogous phenomenon occurs in air. Temperature equilibration occurs on a time scale approximately an order of magnitude longer than it takes air to cross a room, $\tau_{ev}$, although the physical mechanism that allows temperature equilibration is approximately four orders of magnitude slower than $\tau_{ev}$. A Lagrangian analysis allows the fundamental equations to be solved and both phenomena explained. Bridging the gap between derivations using a Lagrangian analysis and the paradigms and presumptions of traditional studies of magnetic reconnection is difficult, so the Lagragian analysis has been largely ignored. The theories of thermal equilibration and magnetic reconnection are developed in parallel to help readers obtain an understanding of the importance and nature of Lagrangian methods.
A. Boozer
Wed, 30 Sep 2020
67/86
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