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Spectral Estimation Techniques for time series with Long Gaps: Applications to Paleomagnetism and Geomagnetic Depth Sounding

机译：大间隙时间序列的频谱估计技术：在古磁性和地磁深度探测中的应用

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摘要

Many Earth systems cannot be studied directly. One cannot measure the velocities of convecting fluid in the Earth's core but can measure the magnetic field generated by these motions on the surface. Examining how the magnetic field changes over long periods of time, using power spectral density estimation provides insight into the dynamics driving the system. The changes in the magnetic field can also be used to study Earth properties - variations in magnetic fields outside of Earth like the ring-current induce currents to flow in the Earth, generating magnetic fields. Estimating the transfer function between the external changes and the induced response characterizes the electromagnetic response of the Earth. From this response inferences can be made about the electrical conductivity of the Earth.;However, these types of time series, and many others have long breaks in the record with no samples available and limit the analysis. Standard methods require interpolation or section averaging, with associated problems of introducing bias or reducing the frequency resolution.;Extending the methods of Fodor and Stark (2000), who adapt a set of orthogonal multi-tapers to compensate for breaks in sampling- an algorithm and software package for applying these techniques is developed. Methods of empirically estimating the average transfer function of a set of tapers and confidence intervals are also tested. These methods are extended for cross-spectral, coherence and transfer function estimation in the presence of noise.;With these methods, new analysis of a highly interrupted ocean sediment core from the Oligocene (Hartl et al., 1993) reveals a quasi-periodic signal in the calibrated paleointensity time series at 2.5 cpMy. The power in the magnetic field during this period appears to be dominated by reversal rate processes with less overall power than the early Oligocene. Previous analysis of the early Oligocene by Constable et al. (1998) detected a signal near 8 cpMy. These results suggest that a strong magnetic field inhibits reversals and has more variability in shorter term field changes.;Using over 9 years of data from the CHAMP low-Earth orbiting magnetic satellite and the techniques developed here, more robust estimates of the electromagnetic response of the Earth can be made. The tapers adapted for gaps provide flexibility to study the effects of local time, storm conditions on Earth's 1-D electromagnetic response as well as providing robust estimates of the C-response at longer periods than previous satellite studies.
机译：许多地球系统无法直接研究。人们无法测量地核中对流流体的速度，但可以测量地表运动引起的磁场。使用功率谱密度估计，检查磁场在长时间内的变化情况，可以深入了解驱动系统的动力学。磁场的变化也可用于研究地球特性-地球外部磁场的变化（例如环电流）会感应电流在地球中流动，从而产生磁场。估计外部变化和感应响应之间的传递函数表征了地球的电磁响应。从该响应可以推断出地球的电导率。但是，这些类型的时间序列以及许多其他时间序列的记录都有很长的间隔，没有可用的样本，从而限制了分析。标准方法需要插值或截面求平均，并伴有引入偏差或降低频率分辨率的问题。扩展了Fodor和Stark（2000）的方法，他们采用了一组正交多锥度来补偿采样中的中断-一种算法开发了应用这些技术的软件包。还测试了根据经验估计一组锥度和置信区间的平均传递函数的方法。这些方法扩展到在存在噪声的情况下进行跨谱，相干和传递函数估计。通过这些方法，对渐新世高度中断的海洋沉积物核心进行的新分析（Hartl等，1993）揭示了准周期的校准的古强度时间序列中的信号在2.5 cpMy下。在此期间，磁场中的功率似乎是由反转速率过程控制的，其总功率低于早期渐新世。 Constable等人对早期渐新世的先前分析。 （1998年）检测到8 cpMy附近的信号。这些结果表明强磁场可以抑制逆转，并且在短期磁场变化中具有更大的可变性。;使用CHAMP低地球轨道磁卫星9年以上的数据以及此处开发的技术，可以更可靠地估计卫星的电磁响应地球可以造出来。适应间隙的锥度提供了灵活性，可以研究本地时间，风暴条件对地球一维电磁响应的影响，并且可以提供比以前的卫星研究更长的C响应的可靠估计。

著录项

  • 作者

    Smith-Boughner, Lindsay.;

  • 作者单位

    University of California, San Diego.;

  • 授予单位 University of California, San Diego.;
  • 学科 Geophysics.;Applied mathematics.
  • 学位 Ph.D.
  • 年度 2016
  • 页码 231 p.
  • 总页数 231
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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