Earth's rotational variations due to rapid surface flows at both boundaries of the outer core

Masao Nakada

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Rapid geomagnetic fluctuations with periods less than a couple of years, so called geomagnetic jerks, are coincident with sharp changes in rate of change of Earth's length of day (LOD) and phase of the Chandler wobble. Here I examine the rotational variations in response to sudden changes of toroidal core surface flows for geomagnetic jerks, assuming rigid rotation of the outer core and core surface flows at both boundaries (CMB and ICB) with the magnitude of ~3 km yr-1. I take into account the gravitational torque acting on the inner core associated with convective processes in the mantle and the electromagnetic (EM) coupling for a model with conductivity of the core of 5 × 105 S m-1 and a 200 m conducting layer of 5 × 105 S m-1 at the bottom of the mantle. The present study indicates that rapid accelerations of the flow at the CMB can produce LOD change consistent with observed LOD derivative with ~0.1 ms yr-1, but do not produce much for the polar motion. On the other hand, rapid accelerations of the flow at the ICB insignificantly affect the LOD change, but can produce polar motion signals that might affect the Chandler wobble if we adopt the EM coupling for a model with the flows of ~3 km yr-1 and root-mean-square value of 4~5 mT for the radial magnetic field at the ICB.

Original languageEnglish
Pages (from-to)235-246
Number of pages12
JournalGeophysical Journal International
Volume184
Issue number1
DOIs
Publication statusPublished - Jan 1 2011

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

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