An Investigation of Magnetic Field Disturbances on the Ground and in the Mesosphere

Abstract

Geomagnetic field models can be a useful tool for when and where there are no measurements available, or access is limited, because of a highly spatially uneven magnetometer network around the globe. The same can be said for altitudes above the ground, but below the ionospheric current layer, where there exist no in situ measurements at the point of writing. Modelled geomagnetic disturbances have been compared with ground magnetometer data to assess the model performance from two different models, the Spherical Elementary Currents System model and the Average Magnetic field and Polar current System model. Additionally a study on the change in geomagnetic disturbances with altitude were included as well. A third method called the Simple Line Current Approximation were added in this study. An assessment on the model performances by rocket magnetometer data studied in Burrows et al. (1971) were attempted to compensate for the lack of in situ measurements from the MOM-campaign, March 2019.

It was found that out of the two advanced models considered, the SECS model had the best performance, with a perfect fit to the measured ground magnetic field. The AMPS model performed poorly when modelling time series of geomagnetic field variations under the auroral zone. However, further model assessment in locations more favourable to magnetic disturbances driven by the solar wind is preferred before a final conclusion can be reached, due to the nature of the model. The assessment of model performance by historic rocket measurements was found to be an inadequate method, due to the large influence by the orientation of the ground geomagnetic field on the ΔB altitude profiles. This meant no conclusion on the accuracy on the model performance for altitudes above 0 km, but below 110 km, could be reached. At locations beneath the auroral zone the ionospheric current system appears too complex to be described by an equivalent current sheet system, or a simple line current, due to the presence of discrete currents in the E-layer. These findings emphasizes the need for a method of measuring the geomagnetic field in the mesosphere.