Auroral and Ionospheric Flow Measurements of Magnetopause Reconnection During Intervals of Northward Interplanetary Magnetic Field

This thesis investigates the coupling between the solar wind and the magnetosphere during intervals of northward interplanetary magnetic field (IMF). The first section uses Super Dual Auroral Radar Network (SuperDARN) data to estimate the high latitude single lobe reconnection rate and relates this to upstream solar wind conditions measured by the Advanced Composition Explorer (ACE) spacecraft. The reconnection rate was found to depend on the IMF direction and magnitude, as well as the solar wind electric field and the length of the merging gap. The second study combines a modified version of the Lockwood ion dispersion model with the Cooling model to characterise the expected ion dispersion signature observed by low or mid altitude spacecraft during intervals of northward IMF. The dependence of the modelled signature on upstream conditions was analysed and found to be in agreement with a small statistical study undertaken using dispersion signature observed by Cluster. A very clear dispersion signature observed by FAST was compared with the predicted modelled signature and found to be in good agreement. The final study presents the theoretical and first observational evidence of dual lobe reconnection at Earth. The threshold clock angle for dual lobe reconnection is calculated for two case studies, as well as the amount of magnetic flux closed. An estimate of the number of particles captured demonstrated that dual lobe reconnection could be the plasma capture mechanism for the cold, dense plasma sheet, although this is thought to require a prolonged period of northward IMF. This study increases our understanding of solar wind-magnetosphere coupling during northward IMF; it also raises further interesting questions and suggests avenues for further work which are discussed at the end of the thesis.