三轴分层地球模型及自转理论

基于Chen & Shen [2010, New estimates of the inertia tensor and rotation of the triaxial nonrigid Earth. Journal of Geophysical Research, 115, B12419, doi:10.1029/2009JB007094] 的理论，结合IAU2000AR06章动-进动模型（国际天文学会推荐的标准模型）采用的MHB2000分层地球模型和目前精度最高的EGM2008、EIGEN-6C等静态全球重力场模型，求解三轴分层地球的各圈层（地幔、外核和内核）的动力学形状参数，包括主惯性矩和动力学扁率（参见表 1）。进而对比研究了三轴性对地球自转理论的影响（参见表2），指出在三轴地球框架下，需要考虑被传统自转理论忽略的地核形变效应。该成果参见陈巍等 [2013, 地球三轴性及频率依赖响应对极移的影响, 中国地球物理学会第二十九届年会, 中国云南昆明, 2013年10月12-16日]。
 表 1  三轴分层地球的动力学形状参数

Parameter		Value
Principal inertia moments of the whole Earth (× 1037 kg m2)	A	8.0100829
	B	8.0102594
	C	8.0364807
Principal inertia moments of the mantle (× 1037 kg m2)	Am	7.0985591
	Bm	7.0987194
	Cm	7.1225467
Principal inertia moments of the core (× 1036 kg m2)	Ac	9.1152379
	Bc	9.1153996
	Cc	9.1393399
Principal inertia moments of the fluid outer core (× 1036 kg m2)	Af	9.0567171
	Bf	9.0568779
	Cf	9.0806773
Principal inertia moments of the solid inner core (× 1034 kg m2)	As	5.8520816
	Bs	5.8521767
	Cs	5.8662552
Polar ellipticity of the whole Earth		3.2845161 × 10–3
Equatorial ellipticity of the whole Earth		2.2033010 × 10–5
Polar ellipticity of the fluid core		2.6455744 × 10–3
Equatorial ellipticity of the fluid core		1.7746896 × 10–5
Polar ellipticity of the solid core		2.4219766 × 10–3
Equatorial ellipticity of the solid core		1.6246969 × 10–5

表 2  三轴地球与旋转对称地球的自转理论的比较

	For triaxial Earth (All parameters take the values listed in Table 1)	For symmetric Earth (All parameters take the values listed in Table 2)
Dynamic  equation
Transfer function
Effective excitation
Chandler frequency
Free core nutation frequency