So Long Kolmogorov

James Beattie (CITA/Princeton)

December 04, 2024

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Abstract: Supernova (SNe) detonations alone provide sufficient energy to power the interstellar medium (ISM) turbulence in our Galaxy. At a conceptual level, SNe-driven turbulence is very different from the regular Kolmogorov (1941) model of turbulence, which is incompressible, isotropic, homogenous, local and has a signed energy flux that moves energy from large to small scales (Kolmogorov’s 4/5ths law). Yet the ISM turbulence community continues to think of the ISM as being described by Kolmogorov-like phenomenology. In this talk I derive the three-mode energy flux transfers functions, allowing me to directly measure the sign and nature of the energy flux at a k mode level. I apply these to SNe-driven turbulence simulations in a multiphase, stratified ISM and reveal that the SNe-driven turbulence has almost no resemblance to Kolmogorov at all, with strong nonlocal transfers and inverse cascades in the incompressible modes, specially where the incompressible energy spectrum admits to a power law. Time-permitting, I will also show that in a medium driven by compressible modes sourced by SNe, the incompressible modes are completely generated within fractal cooling layers between the warm and hot plasma generated by the adiabatic expansion the supernova remnants, making phase mixing the primary source of incompressible mode turbulence in the ISM.