Flux equipartition in astrophysical plasma turbulence.

Expanding plasmas are ubiquitous in the Universe, from supernovae to stellar atmospheres and winds, carrying various forms of energy. Crucial for understanding their behavior, the characterization of the scale-to-scale energy transfer resulting from the interplay of turbulent motions, propagating waves, and instabilities is a key scope of major space missions. Here, we show how simultaneous upscale and downscale energy transfers occur in solar wind, leading statistically to equipartition of the turbulent energy flux. Our study sheds light on the paradigm of the existence of dual energy cascades in astrophysical plasmas, identifying the scales at which energy sources act in the magnetohydrodynamic regime driving turbulent dynamics in solar wind. These findings suggest that a significant fraction of the energy injected into stellar winds at scales much smaller than those of galaxies could be transferred to larger scales through turbulence, potentially influencing star formation processes.