讲座时间：周三（4月24日）下午3点
讲座嘉宾：Fouad Sahraoui
讲座题目：Energy dissipation rate in compressible magneto-plasmas: theory, numerical simulations and in-situ spacecraft observations
讲座地点：北京大学物理楼北415
题目-1
Sub-ion scale turbulence in the near-Earth space: new challenges and future space missions （30分钟）
摘要-1
Sub-ion (kinetic) scale turbulence has been the main focus of research in space plasmas in the last decade because of the crucial role that those scales play in energy dissipation and thus particle energization (heating or acceleration). Yet, several key questions cannot be addressed by those missions or by the upcoming ones (e.g., Parker Solar Probe and Solar Orbiter) because of their instrumental limitations. I will discuss some of these scientific questions and instrumental limitations, then present a new multi-spacecraft mission concept, Debye, designed to solve the problem of turbulence and energy dissipation at electron scales in the solar wind. This mission is currently being considered for selection within the ESA/F1-class call released in 2018.
题目-2
Energy dissipation rate in compressible magneto-plasmas: theory, numerical simulations and in-situ spacecraft observations (30分钟)
摘要-2
A way to study dissipation in turbulent space plasmas is to estimate the total energy cascade rate, which is the energy ultimately dissipated into the system. This was recently achieved within the Earth magnetosheath using an exact law for compressible isothermal MHD turbulence, which highlighted the importance of compressibility in this region. However, to describe the sub-ionic scales where an important part of the dissipation is thought to happen, it is required to go beyond the MHD description of turbulence. It is thus necessary to adapt the widely used ideal MHD models to include (at least) the contribution of the Hall effect at sub-ionic scales. In this presentation I will make a review of previous results on this topic before applying an exact law for compressible Hall-MHD to investigate the influence of the Hall effect on the energy cascade rate. I will show new analytical and numerical results from 3D direct simulations of compressible Hall-MHD for sub-sonic turbulence and first applications to spacecraft data in the SW and magnetosheath. Finally, I will discuss the implications of the results on the turbulence dynamics and energy dissipation at sub-ion scales and the design of future space missions dedicated explore fundamental plasma processes occurring in the near-Earth space.
Biography:
PROFESSIONAL EXPERIENCE
2016- : Senior Scientist (Directeur de Recherches) at CNRS/LPP
SCIENTIFIC RESPONSIBILITIES
PI of the Workpackage « Turbulence » AIDA project 2018-2021 (EU Horizon 2020)
Co-PI of the Workpackage « Turbulence » of LIA (Laboratoire International Associé)MAGNETO France-Argentina : 2017-2021
Co-Head of the Space Plasma Department at LPP (2013-2017)
SPACE MISSION RESPONSIBILITIES
PI of the DBSC experiment on the ESA-JAXA/BepiColombo mission launched to
Mercury on 2018 (Lead CoI of the PWI consortium)
Co-PI of the SCM instrument of the Debye space mission (F1 ESA call, 2018-2019)
AWARDS & GRANTS
2016: NASA/MMS « Group Achievement Award »
2012-1016: ANR Grant Jeune Chercheur (French Science Foundation).
RESEARCH INTERESTS
Waves, turbulence and magnetic reconnection in space and astrophysical plasmas
(linear waves, coherent structures, intermittency, wave-particle interactions)
Space exploration and space instrumentation
