Turbulence, dissipation d’énergie et phénomènes de transport

Turbulence, energy dissipation and transport phenomena

Turbulence, energy dissipation and transport phenomena

  • Number of researchers involved1: about 70
  • Publications (2012-2018)2: more than 600

The ubiquitous "turbulence" in space or fusion plasmas, plays a predominant role in the transport of energy as in the high-energy particles (eg cosmic rays). There are, however, other transport mechanisms in plasmas, such as the radiative transfer - non-turbulent -, the transport of charged particles and the energy deposition in an "ambient" environment (for example the stopping power of the ions described in the FISIC project - Fast Ion-Slow Ion Collisions - carried by the INSP).

The word turbulence covers a wide range of notions and physical questions depending on the environmental conditions. The specific scales associated with these various phenomena are extraordinarily diverse: we are interested in turbulence from macroscopic scales (known as MHD since they are described by magnetohydrodynamics), which extend over the size of our Galaxy in the case of cosmic rays, up to at the microscopic scales at which the kinetics of particles must be studied conventionally, or even quantically. Similarly, the transport of particles and energy in plasma needs descriptions at very different scales, linked to macroscopic transport coefficients, up to the microscopic analysis of instabilities having an influence on transport, or the study of the cross sections of the particle-field interaction.

On the one hand, it is now possible to access new observations produced by space missions (MMS, Solar Orbiter, BepiColombo).

These highlight new microscopic spatial scales and provide a better understanding of the dissipation process of non-collisional plasmas. Researchers will thus be able to better understand what controls dissipation: protons, electrons, heavy ions? Access to this type of experimental data can then be compared to PIC codes, Vlasov, hybrid/fluid codes and will therefore provide a better understanding of where the energy is then transferred.

On the other hand, laboratory astrophysics experiments are used to test several hypotheses related to space plasmas. These experiments already existed in the Labex PLAS@PAR scientific project and they develop.

1The number of researchers given here may involve staff working on several other themes, as well as publications may sometimes relate to several themes.

2Only peer-reviewed journals.

Some major open questions:

  • What are the processes of saturation of turbulence at mesoscale, which are therefore not well described neither from a macroscopic point of view nor from a microscopic point of view? This problem has applications both for fusion and for space plasmas.

  • How to deal with dissipation processes where typical lengths and times vary by several orders of magnitude with multiscale modeling?

Very general questions (mainly methodological), with strong applications in many fields, in particular for fusion or space plasmas. They require theoretical investigations, simulations and experiments including diagnostics such as spectral analysis techniques.

This first theme shows that a synergy between the study of fusion and space plasmas is emerging. Moreover, this theme could also be applied to the modeling of planetary magnetospheres, allowing to better understand radio emissions and, consequently, to identify exo-planets. Finally, the transport of radiation and its transfer in a fluid constitute fields of interest for star formation, fusion, and laser-plasma interaction.

Illustration : Illustration of the BepiColombo space mission launched in October 2018 to which LESIA, LPP and LATMOS contributed through the development of instruments for MPO and MMO probes. © ESA