Modeling magnetic field variations in the daily variation band with ground-based and satellite data
Abstract
Improving models for external magnetic fields in the daily variation (DV) band--periods of several hours to a day or so--is essential for progress on the challenging problem of 3D imaging of mantle electrical conductivity with satellite magnetic data, and would more broadly benefit studies of other internal magnetic field components, through improved data corrections. In this presentation we will summarize progress on a novel approach to empirical modeling of ionospheric magnetic field variations in the DV band. Our approach combines ground and satellite data, as well as outputs of the Thermosphere-Ionosphere-Electrodynamic General Circulation Model (TIE-GCM). Key steps in our approach include: (1) We use frequency domain principal components analysis (PCA) of a network of ~180 ground observatories (1997-2018) to decompose the signal as a sum over a modest number (50-100) of temporal/spatial mode products. The frequency domain temporal modes can be readily inverted to obtain narrow-band functions which are continuous in time, but the spatial modes are sparsely sampled at ground sites. (2) To interpolate (and extend to satellite altitude) the spatial modes, we use basis functions for 3D ionospheric source fields (or currents) derived from PCA of TIE-GCM outputs. Two one year long runs, corresponding to solar minimum/maximum conditions, are used for this step. (3) Basis function coefficients needed to define spatial modes are found by least-squares fitting of ground and satellite data. We will present and compare initial results from fitting ground and satellite data separately and together, and discuss challenges (e.g., allowing for/modeling non-ionospheric sources, non-linear fitting of scalar data, reducing number of required parameters) and possible solutions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGP21B0783E
- Keywords:
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- 1541 Satellite magnetics: main field;
- crustal field;
- external field;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 2499 General or miscellaneous;
- IONOSPHERE;
- 2799 General or miscellaneous;
- MAGNETOSPHERIC PHYSICS;
- 7999 General or miscellaneous;
- SPACE WEATHER