MAGNETIZED PLASMAS IN THE EARLY UNIVERSE

The fluid equations governing a magnetized plasma in a spatially flat Friedmann-Robertson-Walker metric are formulated using the 3+1 formali sm of Thorne and MacDonald. They are the generalization of our previou s work for a zero external field. These equations are first solved in the ultrarelativistic limit where the electron-positron plasma is trea ted. The equations turn out to be conformally invariant, so that the r esults closely resemble those of flat spacetime. The nonrelativistic l imit is then studied in both the matter- and radiation-dominated eras. Here it is found that the various magnetoplasma modes redshift at dif ferent rates, and are governed by the rate of expansion of the Univers e as well as whether the dynamics are dominated by matter or radiation .