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Multipoint Measurements of Magnetic Holes In the Pristine Solar Wind

Masters Thesis Presentation

Tid: On 2020-11-11 kl 13.15

Plats: https://kth-se.zoom.us/j/64621436669

Föreläsare: Henrik Mejergren

Satellite data from the Cluster satellites have been used to find and evaluate structures in the pristine solar wind, referred to as magnetic holes. By using multipoint measurements, size and orientation-estimates are established. Other characteristics of interest are also examined, such as velocity, temperature, and pressure. The results show that the magnetic holes vary in both shape and size, but with a median difference between the minor and major axis by a factor of five. Most of the events also show increases in both density and ion temperature compared to background values. Comparisons have been made with studies of similar structures downstream of the bow shock referred to as plasmoids which show an even more flattened shape in the direction of the plasma velocity. This study did however not find any such correlations when looking at projections in the GSE-coordinate system. This could suggest that these structures are being compressed in the direction of the velocity as they travel past the bow shock, most likely due to the drastic decrease in velocity. Furthermore, no distinct correlation is found between the size of the MH and the drop of magnetic field strength.