On induction effects of geomagnetic daily variations from equatorial electrojet and solar quiet sources at low and middle latitudes

A. Kuvshinov, C Manoj, Nils Olsen, T.J. Sabaka

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    Abstract

    We investigate the spatiotemporal behavior of the magnetic vertical component, Z, of the daily ionospheric current systems: the equatorial electrojet (EEJ) and solar quiet (Sq)variations, considering induction in the mantle and oceans. The inducing EEJ and Sq current systems are provided by the comprehensive model of Sabaka et al.(2004). The three-dimensional (3-D) conductivity model of the Earth includes oceans of laterally variable conductance and a spherical conductor (1-D) underneath. Our model studies demonstrate that induction effects in Z due to the EEJ are negligible everywhere inland for all local times. At CHAMP altitude (400 km) the magnetic signal induced by EEJ above the oceans does not exceed 2–5% of the external field during local noon. This, in particular, means that considering the induction effects is not necessary when modeling the EEJ current strength from inland surface magnetic measurements and/or satellite data. As expected, induction in the oceans strongly affects the Sq field. The model studies show that the anomalous induction effect (defined as the difference between results obtained with 1-D and 3-D conductivity models) of Sq is substantial at CHAMP altitude,comprising 50% of the total field. It is therefore necessary to consider induction in the oceans when modeling Sq variations for both ground-based and satellite data. Finally,we demonstrate that the anomalous behavior of the daily variations in Z at south Indian sites, namely, a large positive prenoon peak, can be explained by 3-D induction of the Sq variations, with no contribution from the EEJ.
    Original languageEnglish
    JournalJournal of Geophysical Research: Atmospheres
    Volume112
    Issue numberB 10
    ISSN2169-9380
    DOIs
    Publication statusPublished - 2007

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