日长的十年尺度波动分析和核幔电磁耦合  

On Analysis of Decade Fluctuation in the Length of Day and Mantle-Core Electromagnetic Coupling

作　　者：顾震年[1] 

机构地区：[1]中国科学院上海天文台

出　　处：《云南天文台台刊》1999年第3期33-40,共8页Publications of the Yunnan Observatoty

摘　　要：分析了１８００ ～１９９５ 年的日长年均值（ △ Ｌ Ｏ Ｄ Ｙ） 观测资料表明：日长（ △ Ｌ Ｏ Ｄ Ｙ） 的十年波动明显大于观测噪声水平。用小波变换方法分析了△ Ｌ Ｏ Ｄ Ｙ 观测资料， 表明△ Ｌ Ｏ Ｄ Ｙ 的十年尺度的周期为６０ａ （ 年） 和３０ａ（ 年） ， 所对应的振幅为１ ｍｓ 和０ ．５ｍｓ 左右。文中采用国际地球自转服务中心提供的（ Ｅ Ｏ Ｐ Ｃ０４９７ 的日长（ △ Ｌ Ｏ Ｄ Ｃ０４９７） 序列以及由美国国家环境预测中心和美国国家大气研究中心（ Ｎ Ｃ Ｅ Ｐ／ Ｎ Ｃ Ａ Ｒ） 利用全球气象资料归算的大气角动量（ Ａ Ａ Ｍ） 序列进行低通滤波分析， 日长和大气角动量在十年尺度上的波动不一致， 大气角动量只影响到日长短于年际以上时间尺度的变化。文中用理论近似来计算核幔电磁耦合力矩的轴向分量， 它与天文观测△ Ｌ Ｏ Ｄ 资料推出的力矩量级相当， 核幔电磁耦合假说可作为△ Ｌ Ｏ ＤAccurate observation of the decade variation in length of day (△LODY)for 1800-1995 has shown that they are most pronouned and well above the observational noise level.Periods with magnitude of order of 60 and 30yr have been found corresponding to peaks of 1ms and 0.5ms respectively by using wavelet transform for △LODY. The low-pass filter analyses with both (△LODC0497) series provided by International Earth Rotation Service (IERS)Analysis Centers and atmosphere anglar momentum (AAM) reduced with the global meteorological data computed by U.S.National Centers for Environmental Prediction (NCEP) have been studied.It is shown from analysis that the △LOD decade variation disagrees with that Of AAM and,however,play an important role in the time scale of shortens to interannual periods. A series of torques for 1800-1995 are derived from the observaed △LODY.We use theoretical approach to compute axial componets of the electromagnetic torque required which is in comparison with torques derived astronomically to explain the decade variation in △LODY. To compare with several core-mantle coupling mechanisms,it may well be concluded from our analysis that,electromagnetic coupling is regarded as one of the most possible mechanism in the decade variation of △LOD.

关 键 词：日长 十年波动 核幔电磁耦合 大气角动量 

分 类 号：P127.4[天文地球—天体测量] P183.2[天文地球—天文学]