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Dissipation and acceleration at the vicinity of dipolarization fronts

Description

The NASA Magnetospheric Multiscale (MMS) mission was successfully launched on 12th of March 2015. As the european 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. Furthermore, the high temporal resolution of the particle detectors which provide the distribution functions at 30ms for electrons and at 150ms for ions also allows to measure the current density independently of the magnetic field measurements. From these diagnostics, one can detect the sudden increases of the magnetic field named « dipolarization fronts » associated with thin current sheets and plasma jets propagating at high-speed through the magnetotail.

A strong energy dissipation and particle acceleration occur at the fronts while the detailed mechanisms are still understood. Such structures have been also observed in the Saturn, Jupiter, and Mercury magnetospheres. Intense lower hybride wave emissions associated with the front density gradients and whistler mode waves dowstream of the fronts [Breuillard et al., GRL, 2016] as well as electromagnetic solitary waves [Le Contel et al., JGR, 2017] have been already identified. A list of typical events is available and a first meso-scale (fluid scales larger than the particle Larmor radius) analysis has been already carried out.

The PhD thesis aims at studying in detail the mechanisms of energy dissipation and transfer near the dipolarization fronts (in particular related to the J.E product, J and E being the current density and the electric field respectively) as well as wave-particle interactions. The MMS data are available including the high-time resolution and many tools for data analysis are already developed (IDL). However, new developments will be needed during the PhD thesis. Numerical simulations using the open « Particle In Cell » code SIMLEI developed by the « maison de la simulation » at Paris-Saclay or based on the 3D hybrid code developed at LPP could be envisaged in order to make some comparisons with the observations.

The PhD student will participate in the weekly LPP MMS meeting (visioconference ~ 10 members) with LPP colleagues and foreign near collaborators. Also, she/he will participate in the weekly international MMS meetings (50-100 members) and will attend the bi-yearly science working team.

Desired profile

Strong background in fundamental physics and in particular in electromagnetisme. Application from a M2 related to electromagnetism is admissible. Specialisation in plasma physics and spatial data analysis will be appreciated . Experience IDL/Matlab.

Structure description
Host laboratory : LPP, Paris
PhD/research supervisor : LE CONTEL Olivier
Email of PhD/research supervisor : olivier.lecontel@lpp.polytechnique.fr
Offer CNES supervisor : AMSIF Kader

To apply, we invite you to contact the PhD/research supervisor and fill, with him/her, the co-financing part of the online application form (Reply to the offer) by April 1st, 2019.

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