MAL27-NP | Lewis Fry Richardson Medal Lecture by Annick Pouquet and NP Division Outstanding ECS Award Lecture by Simone Benella
Lewis Fry Richardson Medal Lecture by Annick Pouquet and NP Division Outstanding ECS Award Lecture by Simone Benella
Convener: François G. Schmitt
| Tue, 16 Apr, 19:00–20:00 (CEST)
Room -2.91
Tue, 19:00

Session assets

Orals: Tue, 16 Apr | Room -2.91

Chairperson: François G. Schmitt
Lewis Fry Richardson Medal Lecture
On-site presentation
Annick Pouquet

Our understanding of turbulence has progressed significantly through combining experiments, observations, theoretical developments, direct numerical simulations and modeling. I will discuss briefly three problems (among many) for which our perception has changed: (i) the derivation of a multitude of exact laws stemming from conservation properties, e.g. in fluid, magnetohydrodynamics (MHD) and Hall-MHD turbulence, and their consequences for constraining scaling relations and dynamical evolutions; (ii) the cascade processes of energy in three dimensional strongly rotating stratified turbulent flows (RST) found to be dual, in the sense that the energy can go in a self-similar manner both to the large scales and to the small scales with (different) contant fluxes, a phenomenon also encountered in MHD, including in solar wind observations; and (iii) turbulent fields themselves (velocity, induction, temperature), together with their gradients, can be intermittent with non-Gaussian wings, as in quantum turbulence and shear flows or in MHD and RST.

I will also mention old and new results concerning the propensity for turbulent flows and nonlinear systems to develop sharp, isolated (intermittent) structures at small and large scales in a variety of physical environments. This will be done in the specific context of normalized moments at third-order (skewness S) and fourth-order (kurtosis K). Indeed, intermittency can be evaluated e.g. through the examination of relations between S and K for fields such as the velocity, temperature and magnetic fields as well as for their local rates of dissipation. The field themselves, in general, have small skewness, but in some cases they display high kurtosis, such as for vertical velocities in RST, as observed in the stable nocturnal planetary boundary layer, as well as for the magnetic field in the solar wind, or more recently in the fast dynamo regime in MHD. On the other hand, the local dissipation rates of these fields follow a parabolic K(S) law whose origin may be linked to kinematic constraints, to the applicability of Langevin models to their dynamics, or to self-organized criticality, as suggested by several authors in various physical contexts, from the atmosphere, the ocean and climate, to fusion plasmas, the solar wind and dwarf galaxies [1,2].

Many thanks to all my collaborators, mentors, colleagues, students and post-docs.

[1] Annick Pouquet, Duane Rosenberg, Raffaele Marino and Pablo Mininni: Intermittency Scaling for Mixing and Dissipation in Rotating Stratified Turbulence at the Edge of Instability. Atmosphere 14, 1375 (2023). Special issue in honor of Jack Herring; B. Galperin, A. Pouquet & P. Sullivan Eds..

[2] Yannick Ponty, Hélène Politano and Annick Pouquet: Spatio-temporal intermittency assessed through kurtosis-skewness relations in MHD in the fast dynamo regime. In preparation (2024).

How to cite: Pouquet, A.: On a few characteristics of geophysical turbulent flows , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10769,, 2024.

NP Division Outstanding Early Career Scientist Award Lecture
On-site presentation
Simone Benella

During the last decades, space missions provided in situ data of diverse space plasma environments with increasingly higher resolution. This enabled the possibility to investigate peculiar properties of fluctuations in the magnetic field and plasma parameters, transitioning from the magnetohydrodynamic (MHD) to the ion-kinetic regime. The ion-kinetic regime is characterized by a global self-similar scaling of fluctuations, in contrast to the local scale-invariance of the MHD ones. In a series of works, we developed a data-driven approach based on the Langevin equation in order to model statistical features of kinetic fluctuations. In practical terms, the stochastic process thus introduced represents the evolution of the magnetic field fluctuations as a function of the scale. As far as such fluctuations are of the Langevin type, their statistics evolve according to a Fokker-Planck equation. Studying the evolution of fluctuation statistics across the scales, e.g., structure functions, allows us to make predictions about global statistical properties, e.g., scaling exponents.

In this work, we review recent results obtained by using data from the ESA/Cluster mission in near-Earth space. We give evidence that the dynamics of magnetic field increments at kinetic scales can be modeled as a stochastic process of the Langevin type, and that the correct scaling law of the structure functions can be obtained through the stochastic equation in the non-diffusive limit, by linking the drift term of the Langevin equation to the Hölder exponent. Finally, this model allows us to derive the asymptotic limit of individual sets of fluctuations, giving thus predictions on the trend expected at kinetic scales.

How to cite: Benella, S.: Exploring space plasma fluctuations at kinetic scales through stochastic process theory, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11136,, 2024.



  • Annick Pouquet, University of Colorado, United States of America
  • Simone Benella, National Institute for Astrophysics, Italy