An attempt to study ion outflow in the polar cusp with conjugated measurements from EISCAT and Cluster
This thesis sought to find ion outflow as measured by Cluster in the polar cusp, in conjunction with ionospheric upflow events observed by the EISCAT radars outside Longyearbyen on Svalbard (ESR). The constraints placed on the identification of these events proved to narrow the total amount of data....
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| Format: | Master Thesis |
| Language: | Norwegian Bokmål |
| Published: |
2005
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| Online Access: | http://hdl.handle.net/10852/11130 http://urn.nb.no/URN:NBN:no-11467 |
| Summary: | This thesis sought to find ion outflow as measured by Cluster in the polar cusp, in conjunction with ionospheric upflow events observed by the EISCAT radars outside Longyearbyen on Svalbard (ESR). The constraints placed on the identification of these events proved to narrow the total amount of data. First of all, Cluster’s magnetic footprint had to pass close by Svalbard’s location. Then, one needed the radars to measure dynamic plasma parameters, which could be interpreted as upflow events. To complete the set, Cluster would also have to observe outflowing O+ particles to confirm that their origin was the ionosphere. After finishing the preliminary search for these data, one pass through the cusp contained data which showed some promise. The outflow event observed by Cluster, could be traced back to an upflow event seen by the ESR, but with a time delay of about 35 minutes. A possible cause for these incidents was found to be a sudden pressure increase in the solar wind occurring at about 10:00 UT. However, to trace a phenomenon through a turbulent region such as the polar cusp across a time span of uptil 45 minutes, cannot be done without admitting that there might be other factors responsible than the ones specifically studied. A significant perturbation of the total magnetic field strength was also investigated with the curlometer technique. This yielded magnetic field aligned currents running both parallel and anti-parallel, as one should expect from a flux tube, more specifically a flux transfer event (FTE). The ExB-velocity was used to identify the tube’s direction of movement, and some investigation of how this velocity would map to the ionosphere was also performed. |
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