EGU2020-711, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-711
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Analysis of Geomagnetic Variability by Empirical Orthogonal Functions

Chi-Hua Chung1,2 and Benjamin Fong Chao2
Chi-Hua Chung and Benjamin Fong Chao
  • 1National Taiwan University, Geosciences, Taiwan (sandyhome3@gmail.com)
  • 2Academia Sinica, Earth Sciences, Taiwan (bfchao@earth.sinica.edu.tw)

We examine the secular variations of global geomagnetic field on long temporal scales using the IGRF model given in Gauss coefficients for 1900 - 2020. We apply the Empirical Orthogonal Function (EOF) analysis to the geomagnetic field truncated at degree 6 and downward continue it to the core-mantle boundary (CMB) under the assumption of an insulating mantle. The first three EOF modes show the periods around 120, 75 and 60 years with corresponding spatial structures. These oscillational modes potentially support the manifestation of magnetic, Archimedes and Coriolis (MAC) waves in the stably stratified layer near CMB (Buffett, 2016). We also model and decompose the geomagnetic field to standing and drifting components according to trajectories of the Gauss coefficients similarly to Yukutake (2015). We then use the Complex EOF (CEOF) analysis on the drifting field. The results indicate the presence of the westward drift phenomenon but only weakly given the fact that the westward drift has only completed a fraction of a cycle during this time.

How to cite: Chung, C.-H. and Chao, B. F.: Analysis of Geomagnetic Variability by Empirical Orthogonal Functions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-711, https://doi.org/10.5194/egusphere-egu2020-711, 2019

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