<title>Spontaneous magnetic field diffusion from laser plasma</title>

Abstract

From the very moment that generation of spontaneous magnetic fields (SMF) in laser plasma has been found experimentally, this phenomenon was treated in a considerable number of publications. These studies were dictated by the importance of this phenomenon for controlled thermonuclear synthesis, as well as for generation of low-frequency currents and fields in a laser flame, from the viewpoint of the conversion of laser radiation into electric energy. The SMF generation mechanisms are rather well explored now. At the same time, the authors believe the available results fail to provide a wholistic and completed picture describing the above processes. In particular, not enough consideration in literature has been given to problems of spatial distribution and time behavior of fields inside and outside plasma with respect to its dynamic and geometric characteristics, as well as problems pertaining to propagation of SMF through conductive shields. This paper attempts at clarifying, to some extent, these topics theoretically. This paper considers part of the field for which the scales of the respective relationships have the same order as the orders of the size of the area occupied by plasma and the time of its life. It is evident that such a field, which is called large-scale, may be obtained by averaging the true field over its fluctuations fast enough in space and time. Clearly, all small-scale components of the field, as they leave plasma, die away very quickly and the outside field becomes fully large-scale. A large-scale magnetic field is characterized by plasma state of a weak nonequilibrium and by processes of charge emission from the laser target. From the viewpoint of macroscopic electrodynamics, the sources of such field are described by density of extraneous currents.