Height Determination of the Acceleration Region for Dayside Occurring Auroral Arcs

• Main Author: Sandström, Gustav
• Format: Others
• Language: English
• Published: KTH, Skolan för teknikvetenskap (SCI) 2014
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-153797

The aim for this bachelor thesis is to determine the altitude of the auroral acceleration region occuring on the dayside. Substantial work has already been done on this topic, but for occurrence at the nightside. In this paper only negative quasi-static potential structures were considered, as they are the main contributor for producing aurora. The data for this study was obtained by the Cluster satellite constellation, and was processed by scripting in MATLAB in order to find the events for this paper. Namely, 17 passages of the auroral oval, especially occurring within two magnetic local time sectors, symmetrically around noon (12 MLT). The results show that the acceleration region occurs from below 2 RE up to an altitude of 4.5 RE with an average of 3.40 ± 0.84 RE, considerably higher than for the nightside. More specifically, fore and afternoon sectors have altitude averages of 2.44 ± 0.49 RE and 4.00 ± 0.26 RE, respectively. A significant difference between the two sectors. By regarding the pseudo altitude and classifying identified events as either -part of a larger scale coherent structure or - a small scaleauroral arc, a general occurrence pattern and height-dependence of the AAR was discovered. The large-scale arcs occur on average at a higher altitude (3.89 ± 0.22 RE) than the small-scale arcs (2.82 ± 0.80 RE).