Neutral Sheets

Abstract

As the theory has progressed, the topic of neutral sheets has developed into an extensive subject area This statement is not based on neutral sheets occurring frequently in nature, though they well may, but on the complexity of the neutral sheet in the geomagnetic tail, which is the best observed and towards which most theoretical work is aimed. It will be found that the structure and behaviour of a neutral sheet depends on the charged particle population in neighbouring regions, so that other cases would require modified models. ‘Neutral sheet’ generally means a thin layer separating regions in which the fields are approximately uniform, but substantially different, and to justify the name the field strength should drop at least an order of magnitude below the strength on either side. A natural simplification, appropriate here, is to assume symmetry so that the fields on the two sides are equal and opposite, except for any small component normal to the sheet. The thinness of the sheet is the one simplifying feature of the problem, but also the reason why the guiding centre approach is invalid, with the consequence that neutral sheets remain a relatively poorly understood part of plasma physics.KeywordsField LinePlasma SheetNeutral LineCanonical MomentumNeutral SheetThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.