Nonlinear string method in magnetospheric and solar physics

Equations of ideal magnetohydrodynamic are written in the special Lagrangian coordinate system with magnetic tube of force as the main under consideration. It is shown that plasma in magnetic field can be considered as a gas of interacting nonlinear strings - tubes of force. The concept of a magnetic tube of force as nonlinear string can be used in the problems with boundary layers ( regions with stretched magnetic field or current layers ). Solution of nonlinear MHD - problems of this type ( including three - dimensional and nonstationary ones ) can be reduced to the series of problems for nonlinear strings (tubes of force). The method enables to include magnetic reconnection into the scheme and may be useful for solution of wide range of problems of physics of magnetosphere and the Sun. First applications of the method of nonlinear string for calculating magnetic barrier and magnetic reconnection are discussed