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Home > About us > Media > Archived news > 2021 > Gautier Nguyen defended his PhD thesis "Study of the coupling between magnetosphere and solar wind with machine learning"
Gautier Nguyen defended his PhD thesis "Study of the coupling between magnetosphere and solar wind with machine learning"
On February 1, 2021, Gautier Nguyen defended his PhD thesis "Study of the coupling between magnetosphere and solar wind with machine learning"
Abstract
Decades of in-situ data measurement by missions focused on the study of the solar wind and its relation with the near-Earth environment allowed the study of the Sun-Earth coupling from a statistical point of view. Nevertheless, these studies are limited by the manual selection of the events of interest in the data that is still a subjective, fastidious and hardly reproducible task.
Using machine learning algorithms, we elaborate automatic detection methods of events from in-situ data measurement. Whether they are applied to the detection of interplanetary coronal mass ejections, to the classification of the near-Earth regions or to the identification of magnetopause magnetic reconnection jets, the developed methods are more accurate than those based on manual, empirical thresholds. They are also adaptable from a mission to another provided the regions visited by the spacecraft are of the same nature. We show that the interpretation of the data by these methods is limited by the vision we have on the data and the events they measure. These methods pave the way for statistical studies of in-situ measured events with an important number of samples. Thereby, we use the classification of the different regions of the near-Earth environment to statistically study the position and shape of the magnetopause using the data of missions with equatorial (THEMIS, MMS, Double Star), polar (Cluster) and lunar (ARTEMIS) orbits. In addition to confirming the seasonal dependence, the azimuthal asymmetry and the influence of the solar wind dynamic pressure, we show that the clock angle of the interplanetary magnetic field modifies the shape of the magnetopause through the process of magnetic reconnection and lead a discussion on the nature of this boundary around the polar cusps. We combine the results of the study into an analytical model of the magnetopause position and shape that offers a more precise description of this boundary on the night side of the Earth magnetosphere.
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