Reconnection Process in the Sun and Heliosphere

Solar flare, coronal mass ejection and many other interesting plasma and magnetic field structures in the heliosphere are believed to be generated by a powerful plasma process widely known as reconnection of magnetic field lines. The basic understanding of this reconnection process is described by considering a simple model suggested by Dungey that contains a kind of consistent flow of plasma around an x-type neutral point. There are, however, several comprehensive MHD models, some of which are also discussed in this article. Spontaneous reconnection based on tearing mode instability is described very briefly for completeness. The crucial role played by magnetic reconnection in violent energy conversion occurring in solar flare, coronal mass ejection and other related phenomena like hard x-ray and soft x-ray emissions is highlighted. Several convincing observational evidences that support reconnection model are presented. Numerical simulation is seen to be an essential part of this study that enhances our understanding of the evolution of plasmoid and multiple shocks due to reconnection of field lines. Some challenges are mentioned towards the end of the presentation.