Asymmetric Ionospheric Equivalent Currents at Magnetic Conjugate Points
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In this thesis we will study high-latitude ionospheric equivalent currents at magnetic conjugate points. The following questions have been addressed in this thesis: What solar zenith angle defines the dark-sunlit terminator? How does the IMF By component affect the correlation between nominal conjugate points? How does the geomagnetic field affect current identities. We will study equivalent currents from their induced magnetic disturbances provided by SuperMAG. SuperMAG provides large dataset covering more than 30 years from more than 400 magnetometers. Interplanetary magnetic field data were provided by NASA OMNIweb from the satellites ACE, IMP-8, Geotail and WIND. Pairs of nominal conjugate stations have been identified and the data have been transformed into appropriate apex quasi-dipole coordinate system. Magnetic perturbation data was used to identify the sunlit-darkness for each magnetometer stations. We found that IMF control of magnetic field lines worsen the correlation of magnetic perturbations, which is probably due to asymmetric currents associated with IMF B_y. Ionospheric conductance has been reported to be scaled with the strength of the magnetic field, which is consistent with our results. We were able to derive an method of determining the scaling factor, but some caution should be used with this result due to statistical uncertainties in our data set.
PublisherThe University of Bergen
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