Modeling the ocean effect of geomagnetic storms

Nils Olsen, A. Kuvshinov

    Research output: Contribution to journalJournal articleResearchpeer-review


    At coastal sites, geomagnetic variations for periods shorter than a few days are strongly distorted by the conductivity of the nearby sea-water. This phenomena, known as the ocean (or coast) effect, is strongest in the magnetic vertical component. We demonstrate the ability to predict the ocean effect of geomagnetic storms at geomagnetic observatories. The space-time structure of the storm is derived from the horizontal components at worldwide distributed observatories from which we predict the vertical component using a model of the Earth's conductivity that a) only depends on depth, and b) includes the conductivity of the sea-water. The results for several strong geomagnetic storms (including the "Bastille Day" event of July 14-15, 2000) show much better agreement (improvement by up to a factor of 2.5) between the observed and the modeled magnetic vertical component at coastal sites if the oceans are considered. Our analysis also indicates a significant local time asymmetry (i.e., contributions from spherical harmonics other than P-I(0)), especially during the main phase of the storm.
    Original languageEnglish
    JournalEarth, Planets and Space
    Issue number5
    Pages (from-to)525-530
    Publication statusPublished - 2004


    • ocean effect
    • geomagnetic storms
    • electromagnetic induction


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