星系密度波的非线性增长

星系螺旋结构的密度波理论受到人们广泛的重视。考虑到波的有限群速度,以及星系激波的耗散,需要解决密度波的长期维持。不少工作采用线性密度波的不稳定模式来补偿波能的耗散,线性波还存在共转奇异性,有必要分析密度波的非线性增长。另一方面,数值试验都发现,在适当物理条件下的螺旋密度波是不稳定的。人们还讨论了非线性星

NONLINEAR GROWTH OF GALACTIC DENSITY WAVES

The unsteady two-dimensional equations of the aerodynamics of the self-gravitational gaseous model have been calculated, using the local solutions of linear density waves as the initial conditions. The results show that there exists rapid nonlinear growth of galactic density waves and the peak value of the fluctuating surface density is equivalent to the basic surface density during the interval of about 5×10~7 years. The evolutional processes of the waves clearly exhibit nonlinear characteristics.