Vis enkel innførsel

dc.contributor.authorLaundal, Karl Magnus
dc.contributor.authorGjerløv, Jesper
dc.contributor.authorØstgaard, Nikolai
dc.contributor.authorReistad, Jone Peter
dc.contributor.authorHaaland, Stein
dc.contributor.authorSnekvik, Kristian
dc.contributor.authorTenfjord, Paul
dc.contributor.authorOhtani, Shin-ichi
dc.contributor.authorMilan, Steve
dc.description.abstractGround magnetic field measurements can be mathematically related to an overhead ionospheric equivalent current. In this study we look in detail at how the global equivalent current, calculated using more than 30 years of SuperMAG magnetometer data, changes with sunlight conditions. The calculations are done using spherical harmonic analysis in quasi-dipole coordinates, a technique which leads to improved accuracy compared to previous studies. Sorting the data according to the location of the sunlight terminator and orientation of the interplanetary magnetic field (IMF), we find that the equivalent current resembles ionospheric convection patterns on the sunlit side of the terminator but not on the dark side. On the dark side, with southward IMF, the current is strongly dominated by a dawn cell and the current across the polar cap has a strong dawnward component. The contrast between the sunlit and dark side increases with increasing values of the F10.7 index, showing that increasing solar EUV flux changes not only the magnitude but also the morphology of the equivalent current system. The results are consistent with a recent study showing that Birkeland currents indirectly determine the equivalent current in darkness and that Hall currents dominate in sunlight. This has implication for the interpretation of ground magnetic field measurements and suggests that the magnetic disturbances at conjugate points will be asymmetrical when the solar illumination is different.en_US
dc.rightsAttribution CC BY-NC-NDeng
dc.titleThe impact of sunlight on high-latitude equivalent currentsen_US
dc.typePeer reviewed
dc.typeJournal article
dc.rights.holderCopyright 2016 The Author(s)en_US
dc.source.journalJournal of Geophysical Research - Space Physics
dc.identifier.citationJournal of Geophysical Research - Space Physics 2016, 121(3):2715-2726

Tilhørende fil(er)


Denne innførselen finnes i følgende samling(er)

Vis enkel innførsel

Attribution CC BY-NC-ND
Med mindre annet er angitt, så er denne innførselen lisensiert som Attribution CC BY-NC-ND