Astrophysicists work to unify turbulence framework to discover weak-to-strong transitions in turbulence

Turbulence is ubiquitous in nature. It is everywhere from our daily lives to the distant universe, and was called “the last great unsolved problem of classical physics” by Richard Feynman. Professor Yan Huirong from the Institute of Physics and Astronomy and DESY at the University of Potsdam and her team have now discovered a long-predicted phenomenon: a weak-to-strong transition in small-amplitude space plasma turbulence.

The discovery was made by analyzing data from ESA’s Cluster mission, a constellation of four spacecraft that fly in formation around Earth and study how the Sun and Earth interact.The research is published in the journal natural astronomy.

The transition from weak to strong Alfvén turbulence is the most critical yet unobserved prediction of magnetohydrodynamic (MHD) turbulence theory over the past three decades. This is very difficult because three-dimensional sampling of turbulent fluctuations is not yet available. Therefore, the research team developed new multi-spacecraft analysis methods to obtain three-dimensional information about velocity and magnetic field fluctuations, allowing direct comparison of observations with theory.

“The observational confirmation of the weak-to-strong transition solves the last puzzle in the MHD turbulence theory: it demonstrates that turbulence self-organizes in an energy cascade process from linear 2D wave-like fluctuations to strong 3D turbulence (i.e. the energy in Plasma Astrophysics at the University of Potsdam Huirong Yan, professor of science and chief scientist at DESY, said the increase in nonlinearity regardless of the initial level of perturbation highlights the pervasiveness of strong MHD turbulence.

As a result, these findings significantly advance our understanding of ubiquitous turbulence, with implications that extend beyond the study of turbulence itself to particle transport and acceleration, magnetic reconnection, star formation, and all other relevant physical processes from Earth to the distant universe.