Comparison of auroral ionospheric and field-aligned currents derived from Swarm and ground magnetic field measurements

L. Juusola, K. Kauristie, H. Vanhamäki, A. Aikio, M. van de Kamp

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Abstract

Derivation of the auroral ionospheric currents from magnetic field measurements can produce drastically different results depending on the data and method used. We have cross tested several methods for obtaining instantaneous field-aligned and horizontal currents from Swarm satellite and International Monitor for Auroral Geomagnetic Effects (IMAGE) ground magnetic field measurements. We found that Swarm can yield latitude profiles of the east-west component of the divergence-free current density at most at ∼200 km resolution, typically resolving the electrojets. The north-south divergence-free component, on the other hand, is not always well reproduced due to the small longitudinal distance between the side-by-side flying satellite pair. Swarm can yield the field-aligned and curl-free current density at a wider range of latitude resolutions (∼7.5–200 km) than the divergence-free current density. While 7.5 km is suitable for comparison with auroras, 200 km typically resolves the Regions 1 and 2 field-aligned currents. IMAGE can yield maps of the divergence-free current density at ∼50 km resolution. Induced telluric currents should be accounted for in the derivation. Not accounting for them in the Swarm analysis, however, does not appear to introduce significant errors. Ionospheric conductances can be estimated by combining the total horizontal current density, consisting of the curl-free and divergence-free components, with the electric field measurements. Our results indicate that Swarm can only yield these at ∼200 km scale size when there is no significant dependence on longitude. However, combining the divergence-free current from IMAGE with the curl-free current and electric field from Swarm could yield conductance maps at ∼50 km resolution.

Original languageEnglish
Pages (from-to)9256-9283
Number of pages28
JournalJournal of Geophysical Research A: Space Physics
Volume121
Issue number9
DOIs
Publication statusPublished - Sep 1 2016

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Magnetic field measurement
field aligned currents
swarms
magnetic fields
ionospherics
density current
divergence
Current density
magnetic field
magnetic effects
current density
monitors
electric field
Electric field measurement
monitoring
Satellites
Ground effect
derivation
telluric currents
ionospheric currents

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Cite this

Comparison of auroral ionospheric and field-aligned currents derived from Swarm and ground magnetic field measurements. / Juusola, L.; Kauristie, K.; Vanhamäki, H.; Aikio, A.; van de Kamp, M.

In: Journal of Geophysical Research A: Space Physics, Vol. 121, No. 9, 01.09.2016, p. 9256-9283.

Research output: Contribution to journalArticle

Juusola, L. ; Kauristie, K. ; Vanhamäki, H. ; Aikio, A. ; van de Kamp, M. / Comparison of auroral ionospheric and field-aligned currents derived from Swarm and ground magnetic field measurements. In: Journal of Geophysical Research A: Space Physics. 2016 ; Vol. 121, No. 9. pp. 9256-9283.
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