Diffusion coefficient in a finite domain from exit times and application to the tokamak magnetic structure
The standard definition of the diffusion coefficient D uses the limit of the mean square excursion; in a finite (bounded) domain this definition is not relevant. But most physical problems deal with bounded systems. A generalization of D, useful to describe transport in a finite region which is a subset of a bounded system can be obtained from the exit times tau(i) of test particles. This paper gives an analytical relation between D and the tau(i) for diffusive processes. The method is applied to compute an averaged diffusion coefficient for collisional particles in a domain between overlapping islands such as exist in a tokamak magnetic configuration, and a discussion given as to whether this process is of a purely diffusive nature.
Bibliographic Reference: Article: Physics Letters A, Vol. 212 (1996) p. 201
Record Number: 199711258 / Last updated on: 1997-10-10
Original language: en
Available languages: en