Context
- 2017 - 2021 - PhD thesis
Our work
Gautier started to work with me for his PhD thesis in 2017 and pioneered with me the use of machine learning methods for detecting signatures in satellite in situ data. These signatures are often very variable from one event to the other and thus hard to find automatically with explicit set of rules.
Download Gautier Nguyen’s thesis
Detecting ICMEs
Interplanetary Coronal Mass Ejections are major plasma and magnetic field structures propagating from the Sun towards the outer heliosphere, sometimes hitting our magnetosphere along the way. Major ones are easily spotted visually in data through their strong and slowly rotating magnetic field, often preceded by a turbulent magnetosheath and a shock wave. However, many are not so easy to spot because many typical features are either missing or very different from their textbook counterpart. Our first work during Gautier’s PhD was a proof of concept for machine learning automatic event detection, applied to the detection of ICMEs in Wind data. This work was published in Astrophysical Journal
Articles
Nguyen et al. (2022)
Modeling the Magnetopause
The magnetopause is the current sheet closing the magnetosphere, roughly parabolic shape whose nose stands at ~10Re from the Earth. In reality, the position and shape of the current surface, and its dependency on solar wind control parameters, are still not very well known. Using a Gradient boosting algorithm Gautier was able to efficiently classify near-Earth data into 3 classes: the solar wind, the magnetosheath and the magnetosphere. This point-wise automatic classification allowed us to build an unprecedented catalog of magnetopause crossing from MMS, THEMIS, Cluster and Double Star missions. Gautier used these thousands of magnetopause crossings to analyze the shape and location of the current sheet, its stand-off location, flaring and asymmetries. This analysis allowed him to later propose a new analytical model of the current sheet. In a final study, Gautier finally confirmed observationally that the magnetopause is indented in the cusp region.
Articles
- Nguyen et al. (2022)
- Nguyen et al. (2022b)
- Nguyen et al. (2022c)
- Nguyen et al. (2022d)
After
Gautier is now (2025) researcher at ONERA Toulouse.