Anomalous Transport Induced by Field Aligned Currents and its Relation to Electromagnetic Coupling

Abstract

The wealth of detailed observations on transport in turbulent plasmas that has become available over the last decade from laboratory experiments, in situ space craft observations and computer simulation demonstrates that in contrast to classical transport, the various steps in the analysis of anomalous transport, involving microscopic processes and the global dynamics, are closely coupled. It also points to many new, exciting, and truly anomalous phenomena. These statements apply especially to the highly dynamic processes connected with field aligned currents. The usually vast difference in time or length scales must allow for considerable simplications in the analysis, depending on the system at hand, but requires careful consideration of the microscopic or macroscopic physics that of necessity is to be treated in a simplified manner. This point is demonstrated by using a marginal stability approach in a numerical model for field aligned currents and electromagnetic coupling in an extended system. Its aim is to see how energy is supplied to a localized dissipation region from a distant generator and how this dissipation in turn affects the global electro-dynamic structure. In addition to the earth's auroral flux tubes, for which this model was primarily designed, these questions are of importance to other extended current systems in astrophysics. Microscopic processes supporting enhanced dissipation and leading to other truly anomalous processes such as acceleration of selected particle groups are then discussed in relation to the global problem.