A new power spectrum and stochastic representation for the geomagnetic axial dipole
A new power spectrum and stochastic representation for the geomagnetic axial dipole
复制标题
地磁轴向偶极子的新功率谱和随机表示
DOI：
10.1093/gji/ggac172
复制
发表时间：
2022
影响因子：
2.8
通讯作者：
Constable, Catherine
中科院分区：
文献类型：
--
作者：
Sadhasivan, Mayuri;Constable, Catherine
地球内部磁场主要由轴向偶极子贡献，其时间变化范围很广，反映了与地磁反转和大规模古长期变化相关的特征时间尺度，从直接观测推断出的年代际和年际变化。我们提出了一个新的经验功率谱的轴向偶极矩的轴向偶极子场的时间变化的复合磁记录的基础上，跨越频率范围为0.1至5 × 105 Myr-1（周期从10万到2年）。新的频谱是用来建立一个随机表示这些时间变化的基础上，3阶自回归（AR）过程，并放置在早期的随机建模研究的背景下。AR参数的估计取决于频率的光谱制度的过渡，并可能受到欧姆扩散，平流和地球的核心扭转振荡。在几个频率范围内的间隔200-5000万年-1（5000年至200年的周期）的经验功率谱位于以上的AR 3模型，并可能受到磁科里奥利（MC）波在地球的核心。的频谱形状和参数估计提供了一个潜在的有用的指导，开发评估是否数值发电机模拟符合标准被认为是地球一样。
Earth’s internal magnetic field is dominated by the contribution of the axial dipole whose temporal variations are wide ranging and reflect characteristic timescales associated with geomagnetic reversals and large scale palaeosecular variation, ranging down to decadal and subannual field changes inferred from direct observations. We present a new empirical power spectrum for the axial dipole moment based on composite magnetic records of temporal variations in the axial dipole field that span the frequency range 0.1 to 5 × 105Myr–1(periods from 10 million to 2 yr). The new spectrum is used to build a stochastic representation for these time variations, based on an order 3 autoregressive (AR) process and placed in the context of earlier stochastic modelling studies. The AR parameter estimates depend on the frequency of transitions in the spectral regime and may be influenced by Ohmic diffusion, advection and torsional oscillations in Earth’s core. In several frequency ranges across the interval 200–5000 Myr–1(5000 to 200 yr periods) the empirical power spectrum lies above the AR3 model and may be influenced by Magneto–Coriolis (MC) waves in Earth’s core. The spectral shape and parameter estimates provide a potentially useful guide for developing assessments of whether numerical dynamo simulations meet criteria for being considered Earth like.