Masters Thesis defence by Anna Willer – Niels Bohr Institutet - Københavns Universitet

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Masters Thesis defence by Anna Willer

Magnetospheric Ring Current Signatures at Ground Level and in Low Earth Orbit

Several studies of the magnetic signal from magnetospheric currents have revealed that the signal derived from global magnetic indices based on ground stations has a significant bias to the signature derived from observations onboard low Earth orbiting satellites. Whether this difference is caused by ionospheric currents, or if it is a consequence of imperfect index derivations, has not yet been investigated in detail.

In this thesis satellite data and a magnetospheric index are analysed in a long term, seasonal and local time perspective. The data are thus categorized in times of different ionospheric conductivity which makes it possible to examine the influence of ionospheric currents. The same analysis is then performed, using one-to-one comparison of data from single observatories with data from satellite near-by overflights. The results of this thesis suggest that imperfect ground-based magnetic index derivation is the most important reason for the found differences.