重力波波包在传播过程中的参量激发  

PARAMETRIC EXCITATION PROCESS OF GRAVITY WAVE PACKETS IN ITS PROPAGATION

作　　者：易帆[1] 

机构地区：[1]中国科学院武汉物理与数学研究所,430071

出　　处：《空间科学学报》1998年第4期313-322,共10页Chinese Journal of Space Science

基　　金：国家杰出青年科学基金!49625407

摘　　要：采用数值方法模拟了重力波波包在向上传播过程中的参量激发．结果表明，通过共振相互作用，两个次级波可由噪声水平发展到相当的强度，并拥有可观的空间范围，但两者获得能量的大小不同，说明在一个共振组中，主波的能量传递具有参数选择性．主波包只将部分能量用来激发次级波，在其能量衰减的同时，波包形状也发生强烈的畸变．波包之间的能量传递具有明显的局地性．由于波包能量交换不再具有可逆性，相互作用的特征时间具有特别重要的意义，它代表绝大多数能量传递发生的时间范围．在特征时间之外，波包之间净的能量传递已相当弱．由中间层向低热层传播的重力波，衰变过程和传播过程可以同步完成．共振相互作用不仅能够使波能量在谱空间扩散，而且能使波能量在物理空间扩展．Parametric excitation is a mechanism to influence the energy transport of internal gravity waves. It manifests itself as a decay of a primary wave and growth of two secondary waves through resonant intetaction. Current research status on this issue stays still at the parametric instability in plane monochromatic internal gravity waves. By using a numerical method the temporal and spatial evolution of parametric excitation in propagating gravity wave packets is studied. It is indicated that through resonant interaction two secondary waves can in sevenal hours reach significant intensities above the noise level and possess considerable space area. The energy amounts which two secondary waves extract from the primary wave are different, exhibiting a parameter dependence of the energy transfer in a triad. The primary wave packet provides only a part of its initial energy to excite secondary waves. The primary wave packet is apparently deformed as it decays. This is caused by the localization in the energy transfer characteristics. The energy transfer among the interacting waves is no longer reversible since the propagating wave packets own limited space area. Thus the characteristic bine for the interaction is of particular significance. It represents a stage in which principal energy transfer arises. Beyond the characteristic bine the net energy transfer among the interacting waves becomes rather weak. The decay process for a gravity wave packet propagating from the mesosphere to the lower thermosphere can cop out sufficiently. Resonant interaction is not only able to diffuse wave energy across spectral space but tends to spread wave energy in physical space.

关 键 词：重力波 参量激发过程 数值模拟 波包 大气 

分 类 号：P433[天文地球—大气科学及气象学]