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Auroral currents pose a challenge for internal magnetic field modeling

Auroral currents pose a challenge for internal magnetic field modeling

A review article on geomagnetic indices reveals that their usage in data selection for internal magnetic field modelling may lead to biased results.

Instead, usage of indices based on global magnetometer networks is recommended, although their original measurements may not always be in the same level as observatory data. During recent 20 years significant progress in internal field modelling has been gained by space-based magnetic field measurements. The three ESA Swarm satellites launched in November 2013 comprise the latest flagship in these activities. Removing the impact of auroral electric currents in Swarm magnetic data is challenging due to their high variable nature. The review article investigates the usability of geomagnetic indices in searching Swarm data with low auroral activity for internal field model construction. Such indices have originally been developed to facilitate event identification in auroral research and they are usually based on data from well-established magnetic observatories. The study reveals that e.g. AE and Kp indices, which are widely used in auroral research, give controversial information about quiescence with 30% probability. The limited spatial coverage of magnetic observatories explains the limited performance of these indices in data selection routines. In validation of internal field models, however, the long-term data archives by magnetic observatories have irreplaceable position. 

More information:

Researcher Kirsti Kauristie, tel. +358 50 597 8874,

Kauristie K., Morschhauser A., Olsen N., Finlay C., McPherron R.L., Gjerloev J.W., Opgenoorth H.J., On the Usage of Geomagnetic Indices for Data Selection in Internal Field Modelling, Space Sci Rev, doi:10.1007/s11214-016-0301-0, 2016.

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