The NASA Magnetospheric Multiscale (MMS) mission was successfully launched on 12th of March 2015. As the European (ESA) Cluster mission, it consists of four identical satellites evolving in a tetrahedral configuration with separations near the electron Larmor radius in the Earth magnetosphere. Such a configuration allows to estimate the local current density from the calculation of the curl of the magnetic field measured on four points (neglecting the displacement current for perturbations with velocity smaller than the speed of light) as well as other observable gradients. Furthermore, the unprecedented high temporal resolution of the particle detectors, which provide the distribution functions at 30ms for electrons and at 150ms for ions, allows to measure the current density independently of the magnetic field measurements.  

The satellites also measure the three-dimensional electromagnetic fields from quasi-static to few kHz and evolve around the Earth along an equatorial orbit with apogees between 12 and 30 Earth radii. Along this orbit, the satellites cross the Earth’s magnetopause many times, the boundary between the solar wind and the magnetosphere. When the interplanetary magnetic field (IMF) transported by the solar wind is oriented southward, magnetic reconnection with the Earth’s magnetic field is favored in the subsolar region. During this process, which has been studied for a long time thanks to various space missions (Geotail, Polar, Cluster, THEMIS, MMS, ...), the magnetic energy is transferred to plasma which is heated and accelerated.  

The PhD thesis aims at studying the dependence of the collisionless magnetic reconnection process on: the presence of magnetospheric cold ions, which can be detected by MMS, on the existence of a magnetic field component perpendicular to the reconnection plane, named guide field and finally on the plasma wave activity. The former two elements are often present in relation to impacts of large-scale perturbations generated by the Sun and transported by the solar wind (coronal mass ejection, corotating interaction regions, streaming interaction regions, ...). They are important as they can modify the energy and mass transfers from the solar wind to the magnetosphere. Indeed, it was shown that the presence of cold ions reduces the reconnection rate and the current density perpendicular to the background magnetic field, enhances the parallel currents and increases the electron pressure gradient normal to the magnetopause, causing an enhancement of the electron decoupling from the magnetic field (Toledo-Redondo et al. 2017, Baraka et al., 2025a,b). On the other hand, the presence of an out-of-plane magnetic field component during the reconnection process can move the reconnection region along the magnetopause and could even inhibit the reconnection process (Swisdak et al. 2003, Pritchett and Mozer, 2009, Eastwood et al. 2012, Aunai et al. 2013, Baraka et al., 2025b). In such conditions, the plasma wave activity associated with the magnetic reconnection process and its effect on the plasma and energy conversion processes has not been studied. 

This PhD project will be carried out by analyzing and comparing in situ measurements from MMS and numerical results from 2D Particle-In-Cell (PIC) simulations, performed with similar plasma conditions using the collaborative SMILEI code. In situ space data, results from numerical simulations as well as tools of data analysis developed in python are available. New kinetic simulations using national high-performance computers (CINES/Adastra) will be run with initial conditions as close as possible of in situ conditions. For the preparation of the new projects of multi-satellite missions HelioSwarm/NASA (1 plateform + 6 small satellites, selected in 2022) and Plasma Observatory/ESA (7 identical satellites, in a competitive Phase A until June 2026) in which LPP is strongly involved, the study of virtual spacecraft trajectories across the simulated reconnection region as well as the development of new multipoint analysis tools are also planned. The PhD student will also collaborate with M. Baraka, J. Dargent  from the LPP space plasma team, with Arnaud Beck form laboratoire Leprince-Ringuet (LLR), and with the international teams from the mentioned space mission in particular J. Burch (MMS PI/SWRI Texas), R. Torbert (MMS coPI, UNH New Hampshire), B. Ergun&N. Ahmadi (LASP, colorado), D. Gershman&K. Bromund (GSFC, Maryland), H. Wei (UCLA, California), Y. Khotyaintsev & D. Graham & C. Norgren (IRF, Uppsala), R. Nakamura (IWF, Graz). He will also join our team of the PHC Procope project funded for 2025-2026 in collaboration with the team of Professor Maria Elena Innocenti of the Institute of Theoretical Physics of the Faculty of Physics and Astronomy, Bochum University. 

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For more Information about the topics and the co-financial partner (found by the lab!); contact Directeur de thèse - olivier.lecontel@lpp.polytechnique.fr

Then, prepare a resume, a recent transcript and a reference letter from your M2 supervisor/ engineering school director and you will be ready to apply online  before March 13th, 2026 Midnight Paris time!