This thesis uses Cluster & Double Star multi-spacecraft missions with support from ground magnetometer and solar wind data to investigate several aspects of the terrestrial mag- netosphere relating to the magnetotail and substorms. The rst study investigated connections between bursty bulk ows (BBFs) detected by the Cluster spacecraft and dipo- larisation detected by the Double Star spacecraft, in the Cluster tail seasons of 2004 & 2005. Simulataneous detections of which were linked heavily to the expansion and recovery phase of substorms. It was found that less than a third of the events can be in any way linked directly. Also, the times when BBFs were detected were distinctly di erent to the times for dipolarisations. The conclusion is that multiple X-lines could be responsible, or simply that these phenomena arise from di erent causes. The second study investigated the statistical ow pro les of BBFs using the Cluster spacecraft. Due to the varied sep- aration distance of the Cluster satellites in 2004 & 2005, the ow channels were probed at two di erent ranges. The typical shape of the ow pro le of BBFs was recovered. The typical width of BBFs was estimated as 2.5 { 3.5 RE. The ow pro le shape was probed for periods of high & low auroral electrojet activity. It was found that the ow width is broader during high activity. This is possibly due to a more well developed reconnection site. The last study investigated the manifestation of azimuthal pressure gradients in the tail plasma sheet in relation to substorms. Use was made of Cluster 1 & Cluster 3 during three case intervals in 2006. Total pressure was evaluated using ion and magne- tometer measurements. It was found that there were no pre-onset pressure gradient build ups, as reported by previous published work. However, pressure gradients were detected for times corresponding to substorm expansion phase and for times without signi cant auroral electrojet activity. The latter may be attributed to pseudo-break up events.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:626576 |
| Date | January 2014 |
| Creators | Duthie, R. J. A. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1427629/ |
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