A comparison and review of steady-state and time-varying reconnection


Reconnection is a ubiquitous energy conversion process operating in current sheets. It appears in a variety of applications and is, for example, the dominant coupling process at the Earth's magnetopause, the current sheet which separates the solar wind and the terrestrial magnetosphere. Reconnection at the magnetopause is investigated theoretically and experimentally, and in both areas a division exists between so-called steady-state and time-dependent reconnection. In theoretical research the former is associated with the time-invariant analysis of Petschek and coworkers, and this is often put into contrast with an intrinsically time-varying process such as tearing. In experimental research, manifestations of reconnection have been classified either as large scale and (quasi) steady-state, or time dependent, with the former corresponding to accelerated plasma flows along the magnetopause, and the latter to the flux transfer event signature. This division is a source of confusion, in particular since it is unlikely that a true steady-state is ever achieved in nature. To clarify the relationship between steady-state and time-dependent reconnection we discuss here an extension of Petschek's analysis to include time variations in the reconnection rate. In this generalized analysis the reconnection electric field is imposed as an initial-boundary condition which can be specified as an arbitrary function of space and time. Different types of reconnection behaviour can therefore be investigated and we take advantage of this to compare steady-state and time-varying reconnection. We show that the former is just a special case of the latter and that there are no jumps in conceptual understanding required from one to the other. Furthermore, the time-dependent analysis is easily understood and gives a framework which unifies the interpretation of reconnection phenomena observed at the magnetopause. In particular, the theoretical results indicate that the same reconnection rate can give rise to both accelerated plasma flows and the flux transfer event signature; thus there is no physical reason to make a distinction in the underlying process giving rise to different reconnection phenomena.

Publication Date


Journal Title

Planetary and Space Science



Digital Object Identifier (DOI)

Document Type