关于地球受迫章动的简正模表达式

章动序列的计算依赖于受迫章动的简正模表达式，简正模表达式涉及到一些系数，包括简正模的本征频率和某些常数。本文讨论了两种不同简正模表达式以及它们的系数间的关系，指出了某些作者给出的系数数值的缺陷，计算了内核动力学对受迫章动的影响，结果表明其影响已在目前ＶＬＢＩ可检测的量级内。章动序列的理论值可通过选定一个地球模型和其它方法推算出，然后将章动序列的理论值与ＶＬＢＩ观测资料进行比较，从而可改进章动序列并为研究模型地球和实际地球的差异提供有用的信息。

ON THE NORMAL MODE EXPANSIONS OF THE EARTH'S FORCED NUTATIONS

Astronomers and geodesists imperatively need a new, more accurate nutaion series, so that they can use it to improve various parameter estimations from the observations.The computation of a nutation series depends on the normal mode expansion of the Earth's forced nutations. The normal mode expansion involves a number of coefficients, including the normal mode eigenfrequencies and some constants. In this paper, two different normal mode expansions and the relations between the various coefficients in the expansions are discussed.The deficiencies of the numerical coefficients estimated by a few authors are pointed out. The relations between the various coefficients should satisfy certain constrained conditions. The influence of inner core dynamics on the forced nutations is determined. The results indicate that its effect can be perceived from VLBI observations. The nutation series can be derived from the normal mode expansion and the coefficients, Which are computed in the light of a selected Earth model (such as PREM ). Then one can analyse VLBI observational data to obtain the corrections to the adopted values. So it will provide useful information for studying the difference between the real Earth and the modeilized Earth.