SEMINÁRIO DO DEPARTAMENTO DE ASTRONOMIA
From Molecular Cloud Filaments to PeVatrons: The Role of Turbulence and Magnetic Fields in the ISM
a talk by Lucas Barreto Mota dos Santos (IAG-USP/Brasil) - In-Person
Abstract:
"Turbulence and magnetic fields play fundamental roles in shaping the interstellar medium across a wide range of physical processes. In this presentation, we will discuss how these forces govern the formation and structure of molecular cloud filaments, and how they can regulate cosmic ray propagation and γ-ray production in the Galaxy. On the structural side, using three-dimensional MHD simulations spanning sub- to super-Alfvénic turbulent regimes, we apply the Histogram of Relative Orientations (HRO) and Projected Rayleigh Statistics (PRS) to characterize filament-field alignment. Sub-Alfvénic clouds preserve magnetic coherence with filaments forming preferentially perpendicular to the field, while super-Alfvénic turbulence and gravity drag field lines into alignment. Comparison with observations suggests consistency with sub-Alfvénic conditions. At the same time, the interplay between turbulence and magnetic fields also shapes the escape and diffusion of cosmic rays. Understanding this relation is critical to the study of Galactic PeVatrons. We will discuss how mirror diffusion, a non-resonant diffusion process present in any MHD system, can help explain the diffusion coefficients needed to reproduce TeV γ-ray observations. Using 3D MHD simulations of a young massive stellar cluster combined with the Monte Carlo CR propagation code CRPropa, we investigate how different diffusion regimes affect the predicted γ-ray spectrum. Using W43 as a benchmark, we find that the observed spectrum from Fermi and LHAASO can be reproduced under different parametrizations, with the diffusion regime playing a key role in determining the relative contributions of inverse Compton scattering and hadronic interactions. Together, these results highlight how turbulence and magnetic fields are key ingredients connecting several different scales of length and energy in the ISM."
Short-Bio:
Bacharel em Física pelo Instituto de Física-USP
Mestrado pelo IAG-USP
Aluno de doutorado do IAG-USP
Google Meet: https://meet.google.com/pcw-gmem-jyi
Link da transmissão: https://www.youtube.com/c/AstronomiaIAGUSP/live