Diffusion of large-scale magnetic fields by reconnection in MHD turbulence

Autor(es)

Santos-Lima, R. ; Guerrero, G. ; Dal Pino, E. M. de Gouveia ; Lazarian, A.

• Tipo de documento: Artigo Científico
• Fonte: Monthly Notices of the Royal Astronomical Society; v. 503, n. 1, p. 20-pg., 2021-03-18.

Resumo

The rate of magnetic field diffusion plays an essential role in several astrophysical plasma processes. It has been demonstrated that the omnipresent turbulence in astrophysical media induces fast magnetic reconnection, which consequently leads to large-scale magnetic flux diffusion at a rate independent of the plasma microphysics. This process is called 'reconnection diffusion' (RD) and allows for the diffusion of fields, which are dynamically important. The current theory describing RD is based on incompressible magnetohydrodynamic (MHD) turbulence. In this work, we have tested quantitatively the predictions of the RD theory when magnetic forces are dominant in the turbulence dynamics (Alfvenic Mach number M-A < 1). We employed the Pencil Code to perform numerical simulations of forced MHD turbulence, extracting the values of the diffusion coefficient eta(RD) using the test-field method. Our results are consistent with the RD theory (eta(RD) similar to M-A(3) for M-A < 1) when turbulence approaches the incompressible limit (sonic Mach number M-S less than or similar to 0.02), while for larger M-S the diffusion is faster (eta(RD) similar to M-A(2)). This work shows for the first time simulations of compressible MHD turbulence with the suppression of the cascade in the direction parallel to the mean magnetic field, which is consistent with incompressible weak turbulence theory. We also verified that in our simulations the energy cascading time does not follow the scaling with M-A predicted for the weak regime, in contradiction with the RD theory assumption. Our results generally support and expand the RD theory predictions. (AU)

• Processo FAPESP: 13/15115-8 - Estudo de efeitos de plasma não-colisional: aplicação ao meio intra-aglomerado de galáxias
• Beneficiário: Reinaldo Santos de Lima
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 13/10559-5 - Investigação de fenômenos de altas energias e plasmas astrofísicos: teoria, simulações numéricas, observações e desenvolvimento de instrumentação para o Cherenkov Telescope Array (CTA)
• Beneficiário: Elisabete Maria de Gouveia Dal Pino
• Modalidade de apoio: Auxílio à Pesquisa - Projetos Especiais
• Processo FAPESP: 09/54006-4 - Um cluster de computadores para o Departamento de Astronomia do IAG-USP e para o Núcleo de Astrofísica da UNICSUL
• Beneficiário: Elisabete Maria de Gouveia Dal Pino
• Modalidade de apoio: Auxílio à Pesquisa - Programa Equipamentos Multiusuários