Training module for doctoral students, regularly proposed by the Doctoral School of Astronomy & Astrophysics of Île-de-France (ED127).
Next edition: 18-22 May 2026.
Location : Meudon Observatory
Registration: https://adum.fr/
Objective: Astrophysical plasmas are often modelled using codes which solve numerically the temporal evolution of fluid quantities such as the density, the pressure or the flow velocity of the plasma in a delimited region of space. Due to their high conductivity, space plasmas often carry strong magnetic fields so that codes based on the equations of standard magnetohydrodynamics (MHD) are generally used for this purpose. Unfortunately, the use of MHD codes can only be thoroughly justified for collisional plasmas, but not for weakly collisional or collisionless plasma such as the solar corona, the solar wind or planetary magnetospheres where the collisional mean free path is of the order of one astronomical unit. A kinetic rather than a fluid description is in principle necessary in this case. The problem is that kinetic simulations are computationally much more costly as the time evolution of the three-dimensional distribution of the plasma’s particles has to be computed at all points of the region under consideration instead of just a few macroscopic quantities such as (e.g.) the density and the pressure. Consequently, kinetic modeling is generally impossible for systems much larger than the so-called kinetic scales, such as the particle’s Larmor radius. Since fluid models are the only viable alternative for large scale collisionless plasmas, it is instructive to explore their limits by comparing fluid and kinetic simulations of a few simple
problems.
Two codes will be used during the training. A fluid code based on the MHD equations and a so-called hybrid code in which plasma ions are treated as particles and electrons as a fluid. We restrict to 1D and 2D problems only so that the simulations can be run on the participants laptops.
Spirit of the training : The training is clearly not about code writing. Participants will simulate some simple pre-defined problems using MHD and hybrid codes. The objective is to interpret the results from a physical point of view. This simulation activity is complemented by courses on astrophysical plasmas (mainly heliospheric plasmas) where the fluid/kinetic duality arises in a crucial way and where one can find equivalents to the elementary problems studied in practical work. Each practical work is followed by a debriefing session, highly appreciated by the participants.
Required level : It is not necessary to have a good background in plasma physics or numerical simulations. However, a minimum interest in both is recommended.
Indicative program:
- Monday: Morning: welcome, introductory course, presentation of a few example problems,
introduction to the numerical codes. Afternoon: Practical work 1 - Tuesday: Morning: Practical work 1, course on the fluid/kinetic duality of a plasma. After-
noon: Practical work 2 - Wednesday: Morning: Practical work 2, Seminar or Course. Afternoon: Practical work 3
- Thursday: Morning: Course on wave-particle resonance. Afternoon: Practical work 4
- Friday: Morning: Practical work 4. Afternoon: Short presentation of some simulations by
the participants and conclusion
Contact : Filippo Pantellini (LIRA, Observatoire de Paris), email : Filippo.Pantellini @ obspm.fr
Supervisors : Nicolas Aunai (LPP), Gérard Belmont (LPP), Filippo Pantellini (LIRA), Roch Smets (LPP)