Studies of nonlinear behaviour in space and astrophysical plasmas

Abstract

The work of this thesis is prepared on the basic of the studies related to some nonlinear behaviours leading to nonlinear wave structures in space and astrophysical plasmas. For such studies, we have formulated some feasible mathematical models under different physical situations that frequently occur either in laboratory or in space plasmas. This thesis consists of nine chapters including the introduction and the conclusion. The piece of work partly deals with the total nonlinearity of the plasma as fluid medium and exact solutions of the arbitrary amplitude nonlinear plasma structures are investigated through the nonperturbative approach. However, the other part is presented by applying the perturbation techniques and studies are limited to small amplitude limit. Chapter 1 is general introduction about plasma, history of plasma research and some applications of plasma studies. Some efforts towards experimental works in tokamak all over the world to generate plasma for fusion reactor are mentioned. Validity of plasma as a fluid and fitness for different nonlinear structure studies in plasma is elaborated. Description of some nonlinear behaviours with earlier history and pioneer works in the line of solitary waves, double layers, sheath, stability etc. are described. Waves in plasma with their dispersion relations are shown briefly. Exploration towards space and astrophysical plasma along with some spacecraft observation is also done. Information about multicomponent plasma such as negative ion plasma, dusty plasma and dust charging is also included in the introduction. Chapter 2 is all about the methods that we have adopted during our work to study some nonlinear behaviours through different standard nonlinear equations. We have explained both perturbative and nonperturbative approaches. Perturbative approach deals with Reductive Perturbation Technique (RPT) leading to well known equations like Korteweg -de Vries (KdV), modified Korteweg -de Vries (mKdV) etc. whereas Modified Reductive Perturbation Technique...