The Earth's core parameters as seen by the VLBI
The Earth's core parameters as seen by the VLBI
复制标题
DOI：
10.1051/0004-6361:20077392
复制
发表时间：
2007-07
影响因子：
6.5
通讯作者：
S. Lambert;V. Dehant
中科院分区：
文献类型：
--
作者：
S. Lambert;V. Dehant
上下文从VLBI章动序列中可以得到流体核的信息，如与逆行自由核章动（RFCN）相关的共振频率。这个频率已经确定，沿着其他参数，然后用更长的数据集进行确认。目标。本文着眼于RFCN频率的灵敏度与三个因素没有考虑之前：国家的最先进的VLBI分析策略，可能的变化的RFCN周期随时间的推移，和大气污染的影响的测定。方法.利用几组VLBI章动数据，我们估计了各种强迫章动的振幅，由此我们推导出由真实的频率和阻尼因子组成的RFCN共振频率。通过使用滑动窗口来检查时间稳定性。大气的贡献进行了评估，使用6小时的NCEP/NCAR再分析数据。结果我们发现，共振周期是稳定的半天内从一个VLBI数据集到另一个。大气角动量的贡献被发现没有明显的影响。然而，我们指出，虽然很小，VLBI数据集之间的不一致，并可能产生影响，如果不加以纠正，在未来的地球物理参数的确定，如果要达到更高的精度比现在。
Context. From the VLBI nutation series, one can derive information on the fluid core, such as the resonant frequency associated with the retrograde free core nutation (RFCN). This frequency has already been determined, along with other parameters, and then later confirmed with a longer data set. Aims. This paper looks at the sensitivity of the RFCN frequency with respect to three factors not considered before: the state-of-the-art VLBI analysis strategy, possible change of the RFCN period with time, and the effects of the atmosphere contaminating the determination. Methods. Using several geodetic VLBI nutation data sets, we estimate amplitudes of various forced nutations, from which we deduce the resonant RFCN frequency consisting in the real frequency and a damping factor. The time stability is checked by using a sliding window. The atmospheric contribution is assessed using the 6-h NCEP/NCAR Reanalysis data. Results. We show that the resonant period is stable within half a day from one VLBI data set to another. The atmospheric angular momentum contribution is found to have no noticeable effect. However, we point out that, although small, inconsistencies between VLBI data sets do show up and could have an impact, if not corrected, in future determination of geophysical parameters, if one wants to reach a higher accuracy than at present.