Analysis of the electric and magnetic fields time variation inside the auroral oval region

Abstract: The Master's thesis is part of a more comprehensive research topic aimed at investigating the interaction between the magnetosphere and the ionosphere. The study of the temporal variation of the eld aligned currents in the auroral region was done through analyzing Electric and Magnetic eld data downloaded from the ESA Cluster Active Archive and gathered through in situ measurements by the tetrahedral Cluster satellite constellation. The four satellites have an almost identical orbit, with a distance separation ranging between a hundred kilometers to several thousand kilometers. This allows for the measurement of the Electric and Magnetic elds associated with Birkeland currents in the same spatial region at four dierent times. By performing a cross-correlation between any two spacecraft measurements we obtain six correlation coecients along with the corresponding time lags, which can then be used to study the lifetime of the associated eld aligned currents. Further data analysis and interpretation is then performed to obtain a better understanding of the temporal stability of auroral structures and the intrinsic coupling between the ionosphere and the magnetosphere.