MHD Instabilities in Accretion Disks and Their Implications in Driving Fast Magnetic Reconnection

Autor(es)

Kadowaki, Luis H. S. ^[1] ; Dal Pino, Elisabete M. De Gouveia ^[1] ; Stone, James M. ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Dept Astron, 1226 Matao St, BR-05508090 Sao Paulo - Brazil

^[2] Princeton Univ, Dept Astrophys Sci, Peyton Hall, Princeton, NJ 08544 - USA

• Tipo de documento: Artigo Científico
• Fonte: ASTROPHYSICAL JOURNAL; v. 864, n. 1 SEP 1 2018.
• Citações Web of Science: 6

Resumo

Magnetohydrodynamic instabilities play an important role in accretion disk systems. Besides the well-known effects of magnetorotational instability (MRI), the Parker-Rayleigh-Taylor instability (PRTI) also arises as an important mechanism to help in the formation of the coronal region around an accretion disk and in the production of magnetic reconnection events similar to those occurring in the solar corona. In this work, we have performed three-dimensional magnetohydrodynamical (3D-MHD) shearing-box numerical simulations of accretion disks with an initial stratified density distribution and a strong azimuthal magnetic field with a ratio between the thermal and magnetic pressures of the order of unity. This study aimed at verifying the role of these instabilities in driving fast magnetic reconnection in turbulent accretion disk/corona systems. As we expected, the simulations showed an initial formation of large-scale magnetic loops due to the PRTI followed by the development of a nearly steady-state turbulence driven by both instabilities. In this turbulent environment, we have employed an algorithm to identify the presence of current sheets produced by the encounter of magnetic flux ropes of opposite polarity in the turbulent regions of both the corona and the disk. We computed the magnetic reconnection rates in these locations, obtaining average reconnection velocities in Alfven speed units of the order of 0.13 +/- 0.09 in the accretion disk and 0.17 +/- 0.10 in the coronal region (with mean peak values of order 0.2), which are consistent with the predictions of the theory of turbulence-induced fast reconnection. (AU)

• 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
• Processo FAPESP: 16/12320-8 - Estudo numérico de reconexão magnética ao redor de buracos negros
• Beneficiário: Luis Henrique Sinki Kadowaki
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado