Soutenance de thèse de Bayane Michotte de Welle - 22 mars 2024 à 14h

Annonce transmise par Nicolas Aunai (LPP)

I would like to invite you to my PhD defense, taking place on Friday March 22nd at 2pm in Amphitheatre Becquerel, Ecole Polytechnique, entitled:

"Statistical Study of the Global Constraints Governing Magnetic Reconnection at the Earth's Magnetopause"

Abstact :

Magnetic reconnection is the primary mechanism through which the Earth's magnetosphere couples to the surrounding magnetized solar wind. The efficiency of this coupling largely depends on where the reconnection occurs on the magnetopause. Determining the location of so-called reconnection X-lines, as a function of the upstream interplanetary conditions, remains a long-standing challenge in magnetospheric physics due to its multiscale character. Progress is hampered by the fact that the plasma and field properties that constrain where reconnection can develop on the magnetopause are themselves poorly understood, and so far only accessed through global magnetohydrodynamics simulations. This thesis brings new observational constraints to this problem through the reconstruction of 3D global spatial variations of the plasma and magnetic field on the dayside magnetosheath and magnetopause..
A new methodology was developed to collect and process two decades of in-situ measurements from the Cluster, Double Star, THEMIS, and MMS missions
We first reconstructed the global 3D magnetic draping of the interplanetary magnetic field (IMF) in the magnetosheath, whose structure is demonstrated to be controlled by the plasma flow in this region in a way that invalidates widely used vacuum magnetostatic draping assumptions in about 30% of the IMF orientations.
We then examine the variation of magnetic field amplitude and plasma density in the magnetosheath and their dependence on the IMF orientation, and highlight their nonlinear coupling with magnetopause reconnection.
Finally reconstructions of the spatial distributions magnetic shear, current density and reconnection rate on the dayside magnetopause,for different dipole tilts and IMF orientations, allowed us to better understand the interplay between local and global constraints on the location of reconnection X-lines.
 
Supervisors:
- Nicolas Aunai
- Roch Smets
 
 
Jury:
 
Benjamin Grison, Institute of Atmospheric Physics, Prague - Rapporteur
Alexis Rouillard, IRAP - Rapporteur
Aurélie Marchaudon, IRAP
Frédéric Baudin, IAS
Michael Hesse, NASA
 
You are cordially invited to the drink party after the defense in the Jean-Lascoux room in Aile 0 in LPP, Palaiseau
 
 
A zoom access is available : https://cnrs.zoom.us/j/95630594271?pwd=dnBJRCtSS0tGdkhtOE9EQU13QTdsUT09
ID de réunion: 956 3059 4271
Code secret: kaxu9e