Nonlinear magneto-acoustic waves in the solar atmosphere

The weakly nonlinear evolution of quasi-isentropic magnetoacoustic waves in the solar atmosphere is analyzed. The plasma is assumed to be initially ho mogeneous, in thermal equilibrium and with a straight and homogeneous magne tic field frozen in. Additionally, the plasma is assumed to be cooled by th e standard cooling function in the range of 10(4) K < T < 10(7) K and heate d by a mechanism which is proportional to the density and temperature. The range of temperature where the plasma is isentropically unstable, the e-fol ding time for thermal instability and the corresponding time and length-sca le for wave breaking are found. (C) 2001 Elsevier Science B.V. All rights r eserved.