Diffusion of large-scale magnetic fields by reconnection in MHD turbulence
Carregando...
Data
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Federal de Minas Gerais
Descrição
Tipo
Artigo de periódico
Título alternativo
Primeiro orientador
Membros da banca
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 (Alfvénic Mach number MA < 1). We employed the Pencil Code to perform numerical simulations of forced MHD turbulence, extracting the values of the diffusion coefficient ηRD using the test-field method. Our results are consistent with the RD theory (ηRD∼M3A for MA < 1) when turbulence approaches the incompressible limit (sonic Mach number MS ≲ 0.02), while for larger MS the diffusion is faster (ηRD∼M2A). 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 MA predicted for the weak regime, in contradiction with the RD theory assumption. Our results generally support and expand the RD theory predictions.
Abstract
Assunto
Campos magnéticos, Estrelas, Difusão
Palavras-chave
Magnetic fields, Magnetic reconnection, Magnetohydrodynamic, Turbulence, Stars
Citação
Departamento
Curso
Endereço externo
https://academic.oup.com/mnras/article/503/1/1290/6144594