Description of turbulent dynamics in the interstellar medium: multifractal-microcanonical analysis

Observations of the interstellar medium (ISM) show a complex density and velocity structure, which is in part attributed to turbulence. Consequently, multifractal formalism should be applied observation maps ISM order characterize its turbulent multiplicative cascade properties. However, formalism, even more advanced recent canonical versions, requires large number realizations system, usually cannot obtained astronomy. We present self-contained introduction “microcanonical” version, allows us, for first time, compute precise turbulence characteristic parameters from single observational map without need averages grand ensemble statistical observables (e.g., temporal sequence images). singularity exponents spectrum both observations magnetohydrodynamic simulations, include key describe ISM. For we focus on 250 ?m Herschel Musca filament. Scaling properties are investigated using spatial 2D structure functions, apply two-point log-correlation magnitude analysis over various lines observation, known directly related existence under conditions. It reveals clear signature with an inertial range 0.05–0.65 pc. that proposed microcanonical approach provides spectra truly scale invariant, as required validate any method used analyze multifractality. The Musca, sufficiently clearly not symmetric observed log-normal behavior. claim toward features log-Poisson shape. Since behavior claimed exist when dissipation stronger rare events flows, contrast homogeneous (in volume time) events, suggest this deviation log-normality could trace enhanced at small scales, may explain, or least consistent with, dominant filamentary Musca. Moreover, find subregions tend different properties: While few regions can described by model, other have better fitted model. This strongly suggests types dynamics inside cloud. note these differences between appear only after reducing noise features, sparse edge-aware algorithm, tendency “log-normalize” map. Implications star formation process discussed. Our study establishes fundamental tools will galactic clouds simulations forthcoming studies.