Magnetic effects of magnetospheric currents at ground and in low orbit

Research output: Research - peer-reviewConference abstract for conference – Annual report year: 2012

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Since the advent of high precision vector magnetic field observations from satellites in low orbit it has been recognized that magnetospheric currents contribute by about 20nT to the geomagnetic field even during quiet times (when Dst=0nT) (Langel et al., 1980). Comparing spherical harmonic models of the magnetospheric field derived from ground observations with satellite data shows a similar offset. A robust linear fit between these two quantities reveals a slope of about 0.9, indicating that only 90% of the magnetospheric field as monitored on ground is seen by satellites. The intercept of ~20nT is found to diminish with reducing solar activity (as was previously noted by Lühr & Maus, 2010), while the slope is hardly affected. There have been several suggestions for the origin of this systematic difference between ground and space based observations of magnetospheric fields. We compare magnetic residuals of selected observatories with those of CHAMP satellite observations at times of conjunctions, separating the data pairs by criteria including local time and longitude, season, solar and magnetic activity. Obtaining rough estimates of the ionospheric conductivity in this way, we are able to discuss possible ionospheric sources for the observed intercept. Consideration of appropriate ordering in local time, also enables us to test for possible contributions from field aligned currents connecting the ionosphere and the magnetosphere. Langel RA, Mead GD, Lancaster ER, Estes RH, Fabiano EB. 1980. Initial geomagnetic field model from Magsat vector data. Geophys. Res. Lett. 7:793-96 Lühr H, Maus S. 2010. Solar cycle dependence of quiet-time magnetospheric currents and a model of their near-Earth magnetic fields. Earth Planets Space 62:843-48
Original languageEnglish
Publication date2012
Number of pages1
StatePublished - 2012
Event2012 AGU Fall Meeting - San Francisco, United States
Duration: 3 Dec 20127 Dec 2012
Conference number: 45
http://fallmeeting.agu.org/2012/

Conference

Conference2012 AGU Fall Meeting
Number45
CountryUnited States
CitySan Francisco
Period03/12/201207/12/2012
Internet address

    Research areas

  • Geomagnetism And Paleomagnetism, Satellite magnetics, Main field, Crustal field, External field, Ionosphere, Current systems, Magnetospheric Physics, Ring current, Space Weather, Models
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