TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 65 (No. 11), pp. 1309-1317, 2013

Swarm SCARF equatorial electric field inversion chain

Patrick Alken1,2, Stefan Maus1, Pierre Vigneron2, Olivier Sirol2, and Gauthier Hulot2

1National Geophysical Data Center, NOAA, Boulder, Colorado, U.S.A.
2Equipe de Géomagnétisme, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, UMR 7154 CNRS, 1 rue Jussieu, F-75005, Paris, France

(Received March 19, 2013; Revised September 9, 2013; Accepted September 10, 2013; Online published November 22, 2013)

Abstract: The day-time eastward equatorial electric field (EEF) in the ionospheric E-region plays a crucial role in equatorial ionospheric dynamics. It is responsible for driving the equatorial electrojet (EEJ) current system, equatorial vertical ion drifts, and the equatorial ionization anomaly (EIA). Due to its importance, there is much interest in accurately measuring and modeling the EEF for both climatological and near real-time studies. The Swarm satellite mission offers a unique opportunity to estimate the equatorial electric field from measurements of the geomagnetic field. Due to the near-polar orbits of each satellite, the on-board magnetometers record a full profile in latitude of the ionospheric current signatures at satellite altitude. These latitudinal magnetic profiles are then modeled using a first principles approach with empirical climatological inputs specifying the state of the ionosphere. Since the EEF is the primary driver of the low-latitude ionospheric current system, the observed magnetic measurements can then be inverted for the EEF. This paper details the algorithm for recovering the EEF from Swarm geomagnetic field measurements. The equatorial electric field estimates are an official Swarm level-2 product developed within the Swarm SCARF (Satellite Constellation Application Research Facility). They will be made freely available by ESA after the commissioning phase.
Key words: Equatorial ionosphere, electric fields, space magnetometry, Swarm.

Corresponding author E-mail: patrick.alken@noaa.gov

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