CNR ExploRA

Articolo in rivista, 2019, ENG, 10.3389/fphy.2019.00108

Sign Singularity of the Local Energy Transfer in Space Plasma Turbulence

Sorriso-Valvo, Luca; De Vita, Gaetano; Fraternale, Federico; Gurchumelia, Alexandre; Perri, Silvia; Nigro, Giuseppina; Catapano, Filomena; Retino, Alessandro; Chen, Christopher H. K.; Yordanova, Emiliya; Pezzi, Oreste; Chargazia, Khatuna; Kharshiladze, Oleg; Kvaratskhelia, Diana; Vasconez, Christian L.; Marino, Raffaele; Le Contel, Olivier; Giles, Barbara; Moore, Thomas E.; Torbert, Roy B.; Burch, James L.

Escuela Politecn Natl; CNR; Politecn Torino; Iv Javakhishvili Tbilisi State Univ; Univ Calabria; Serco Italia ESA ESRIN; Sorbonne Univ; Queen Mary Univ London; Swedish Inst Space Phys; Gran Sasso Sci Inst; INFN; Iv Javakhishvili Tbilisi State Univ; Sokhumi State Univ; Univ Claude Bernard Lyon; NASA; Univ New Hampshire; Southwest Res Inst

In weakly collisional space plasmas, the turbulent cascade provides most of the energy that is dissipated at small scales by various kinetic processes. Understanding the characteristics of such dissipative mechanisms requires the accurate knowledge of the fluctuations that make energy available for conversion at small scales, as different dissipation processes are triggered by fluctuations of a different nature. The scaling properties of different energy channels are estimated here using a proxy of the local energy transfer, based on the third-order moment scaling law for magnetohydrodynamic turbulence. In particular, the sign-singularity analysis was used to explore the scaling properties of the alternating positive-negative energy fluxes, thus providing information on the structure and topology of such fluxes for each of the different type of fluctuations. The results show the highly complex geometrical nature of the flux, and that the local contributions associated with energy and cross-helicity non-linear transfer have similar scaling properties. Consequently, the fractal properties of current and vorticity structures are similar to those of the Alfvenic fluctuations.

Frontiers in Physics 7 , pp. 108-1–108-11