10:45 AM - 12:15 PM
[SEM15-P11] On spatial and time variations of magnetic field in asymptotic geodynamo solution
Keywords:Geodynamo, Geomagnetic field, Secular variations
In order to extract the dynamics of Earth’s core from observed geomagnetic field, it is essential to find the direct link between observational geomagnetic field and its generation mechanism such as MHD dynamo actions. Nakagawa and Davies (2022) examines the compliance between observed geomagnetic field and magnetic field in asymptotic geodynamo solutions (This solution may be accessible to the realistic situation of Earth’s core with extrapolating the physical properties) from views of characteristic length-scale of MHD dynamo actions and kinetic energy production compared to magnetic energy production, which tries to seek the direct link between observation and physical processes. However, that investigation does not deeply discuss the timescale of dynamics in the asymptotic geodynamo solution and secular variations of geomagnetic field derived from observations. In this study, for providing an additional constraint on asymptotic geodynamo solution, we attempt to seek the more direct link between observational geomagnetic field and asymptotic geodynamo solution with the timescale of magnetic field variations (secular variations and accelerations).
An example of cases in asymptotic geodynamo solutions in Nakagawa and Davies (2022) is used to compute the secular variations and secular accelerations. With time-windowing of time series data of magnetic field in 1 to 400 years, the secular variations and accelerations indicates the similar profiles to the observational data up to degree 6 of Gauss coefficients and does not depend on the width of time-windowing applied here. This result may suggest that the asymptotic geodynamo solution can be more useful for finding the direct link between physics and observations to understand the generation mechanism of geomagnetic field. However, the more detailed check should be done for revealing the dynamics of Earth’s core in this asymptotic geodynamo solution.
An example of cases in asymptotic geodynamo solutions in Nakagawa and Davies (2022) is used to compute the secular variations and secular accelerations. With time-windowing of time series data of magnetic field in 1 to 400 years, the secular variations and accelerations indicates the similar profiles to the observational data up to degree 6 of Gauss coefficients and does not depend on the width of time-windowing applied here. This result may suggest that the asymptotic geodynamo solution can be more useful for finding the direct link between physics and observations to understand the generation mechanism of geomagnetic field. However, the more detailed check should be done for revealing the dynamics of Earth’s core in this asymptotic geodynamo solution.