Recent Progress in Solar Physics

A number of significant recent advances in solar physics are reviewed. New kinds of observations made during the present sunspot cycle, which began in 1954, have emphasized still further the apparent complexity of solar phenomena and the need of nonequilibrium theoretical treatments. Among the new developments di cussed are solar cosmic rays and highenergy particles, flares and prominences, coronal condensations, solar magnetic fields, and solar radio noise mission. Theoretical nalyses of the conditions of the solar atmosphere as a hot plasma, and as a gaseous ensemble exhibiting ross departures from thermodynamic equilibrium, are discussed. New work on atomic collisional parameters is also reviewed. The article concludes with a synopsis of certain major unsolved problems of the solar atmosphere.