Influences on the location of the Earth’s magnetopause

The magnetopause is the boundary that separates the Earth’s magnetic field from the interplanetary magnetic field (IMF) and largely prevents solar wind plasma from entering the magnetosphere. It shields the Earth from space weather and understanding what affects its location is vital as we become more dependent on ground-, air- and space-based technologies. To study influences on the location of the magnetopause, an automated magnetopause crossing detection routine is developed which can determine the location of the magnetopause using a combination of plasma and magnetic field data. The technique is applied to almost two solar cycles of data (1996 - 2015) from the Geotail spacecraft, producing a database of over 8000 magnetopause crossings. The crossings are normalised for solar wind dynamic pressure and the magnetopause is modelled with the functional form of the Shue et al. [1997, 1998] empirical model. Solar cycle effects on the shape and location of the magnetopause are investigated and the model is compared to models defined by previous authors. Magnetopause location varies significantly throughout the solar cycle. We find that the model developed in this thesis characterises magnetopause location most accurately during solar minima but is less accurate during the increased solar activity observed in the declining phase of solar cycle 23. Finally, we compare the model magnetopause predictions with observations for a variety of solar wind and magnetospheric conditions. We find that the direction of the BZ component of the IMF has a stronger influence on the dayside magnetopause when the solar wind dynamic pressure is weaker. The quantity of open magnetic flux in the magnetosphere orders the dayside magnetopause location. We also examine the effect of the ring current on magnetopause location and results indicate that the dayside magnetopause is eroded and magnetotail is more inflated when the ring current is stronger.