Validating Magnetopause Models using Cluster Observations

Lewis, Samuel and Wild, Jim (2026) Validating Magnetopause Models using Cluster Observations. Masters thesis, Lancaster University.

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Abstract

Earth’s magnetosphere protects the terrestrial atmosphere from the solar wind and the interplanetary magnetic field. The magnetopause is the boundary between the magnetosheath and the magnetosphere, acting as the edge of the region of space dominated by Earth’s magnetic field and plasma. Therefore, the location and geometry of the magnetopause are important properties to understand in order to facilitate better planning for satellite investigations within this region, and to reveal the natural process underpinning space weather. Using the Cluster mission, this dissertation investigates the size and shape of Earth’s magnetopause, to test the validity of current magnetopause models. It is found that the Cluster data and the models agree with at most a 15% disagreement over all latitudes and local times. The greatest disagreement between models arises with the magnetospheric cusp region as this feature is not included in the cylindrically symmetric Shue et al. (1998) model, but is included in the asymmetric Lin et al. (2010) and Liu et al. (2015) models; models that are relatively simple to compute in comparison to other magnetopause models that include this cusp region. The validity of the newly introduced Geospace Region and Magnetospheric Boundary dataset (GRMB), developed by Grison et al. (2025), has been briefly tested. This proves a useful resource for identifying the region Cluster is in. However, this database includes some inaccurate magnetopause crossings, featuring spatial ambiguities up to 15 Earth Radii for some cases. Overall, this dissertation confirms that the GRMB database can be a useful resource provided caution is used with some identified regions, and that some of the currently used magnetopause models are broadly accurate with some drawbacks in certain regions, although this is dependant on the precision required.