EGU2020-13127
https://doi.org/10.5194/egusphere-egu2020-13127
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Length of day fluctuations at long and short timescales. Geomagnetic drivers

Crisan Demetrescu and Venera Dobrica
Crisan Demetrescu and Venera Dobrica
  • Institute of Geodynamics, Romanian Academy, Bucharest, Romania (crisan@geodin.ro)

We decompose the well known LOD time series provided by IERS, that shows so-called decadal variations, in fluctuations at several timescales, namely: sub-centennial (60-90 years), inter-decadal (20-35 years), decennial (~11 years) and intra-decennial (~6 years). A Hodrick and Prescott (1977) type of analysis is used, followed by the decomposition of the trend and oscillatory parts at the mentioned timescales using Butterworth filtering. Comparing the results to previously (e.g. Dobrica et al., 2018) known oscillations of the geomagnetic field (dD/dt), and carrying out a similar analysis for parameters describing the evolution of the magnetospheric ring current, suggest the latter is the ultimate driver of both geomagnetic and LOD variations. The probable mechanisms are discussed as well: Alfvén torsional oscillations in the outer core, triggered by variations in the magnetospheric ring current, or a direct control of geomagnetic declination by variations in the magnetospheric ring current. While the first one is long accepted for the long-term variations in D and LOD, a similar possibility for the 6-year variation is out of question due to the implied value of the geomagnetic field within the outer core (Gillet et al., 2010); for the latter we suggest the second mechanism.       

How to cite: Demetrescu, C. and Dobrica, V.: Length of day fluctuations at long and short timescales. Geomagnetic drivers, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13127, https://doi.org/10.5194/egusphere-egu2020-13127, 2020

Display materials

Display file