MAGNETIC TOPOLOGY AND THE PROBLEM OF ITS INVARIANT DEFINITION

The evolution of an ideal plasma conserves magnetic lines of force and hence magnetic topology. However, magnetic topology, i.e. the structu re and linkage of magnetic flux, is a property of the magnetic field a lone. Therefore, the conservation of topology can also be a property o f non-ideal plasmas for which the plasma flow is not line conserving. A general definition of magnetic topology is given and it is shown tha t it yields a large set of non-ideal topology-conserving systems. In t he application of the notion of magnetic topology to real plasmas prob lems arise concerning the stability of topology. Instability may inhib it one from defining the topology of a given real, i.e. not exactly pr escribed, magnetic field configuration and makes it difficult to detec t changes of magnetic topology, such as reconnection processes. This p roblem of structural instability of magnetic topology also appears in connection with changes of the frame of reference. A change of the fra me of reference may lead to a transition in topology especially for to pological unstable, non-ideal systems. (C) 1996 American Institute of Physics.