4:15 PM - 4:30 PM
[MGI30-10] Geodynamo data assimilation for candidate models of IGRF13-SV from Japan team
Keywords:IGRF, Data assimilation, dynamo
We employ data assimilation with geodynamo calculations to generate a SV candidate model for the period from 2020.0 to 2025.0. Although the two standard approaches, (1) adoption of SV at the IGRF release time and (2) spline extrapolation of the main field in the future, are common for generating SV candidates, they are not “physics-based” forecasts, and, intrinsically, cannot alleviate the effect of sudden changes in the SV field called “geomagnetic jerks” (Mandea et al., 2010). In this context, data assimilation is one of novel approach to obtain an appropriate initial condition for geodynamo calculations at the time of IGRF release time. Since the parameters used in geodynamo calculations are apart by some orders of magnitude from those for the Earth's core, it is not appropriate to take geodynamo solutions as they are for the predictions. Nevertheless, it is possible to rescale the time-axis of geodynamo calculations using the ratio of the so-called “secular-variation time-scale” (Chlistensen and Tilgner, 2004) between the geomagnetic field and geodynamo calculations. In this presentation, we are going to show candidate models of secular variation obtained by geodynamo data assimilation with discussions on the time-scales, the method of assimilation, and data-set employed for the assimilation.