FAST MAGNETIC FIELD AMPLIFICATION IN THE EARLY UNIVERSE: GROWTH OF COLLISIONLESS PLASMA INSTABILITIES IN TURBULENT MEDIA

Autor(es)

Falceta-Goncalves, D. ^{[1, 2]} ; Kowal, G. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Escola Artes Ciencias & Humanidades, BR-03828000 Sao Paulo, SP - Brazil

^[2] Univ St Andrews, Sch Phys & Astron, SUPA, St Andrews KY16 9SS, Fife - Scotland

• Tipo de documento: Artigo Científico
• Fonte: ASTROPHYSICAL JOURNAL; v. 808, n. 1 JUL 20 2015.
• Citações Web of Science: 9

Resumo

In this work we report on a numerical study of the cosmic magnetic field amplification due to collisionless plasma instabilities. The collisionless magnetohydrodynamic equations derived account for the pressure anisotropy that leads, in specific conditions, to the firehose and mirror instabilities. We study the time evolution of seed fields in turbulence under the influence of such instabilities. An approximate analytical time evolution of the magnetic field is provided. The numerical simulations and the analytical predictions are compared. We found that (i) amplification of the magnetic field was efficient in firehose-unstable turbulent regimes, but not in the mirror-unstable models;. (ii) the growth rate of the magnetic energy density is much faster than the turbulent dynamo;. and (iii) the efficient amplification occurs at small scales. The analytical prediction for the correlation between the growth timescales and pressure anisotropy is confirmed by the numerical simulations. These results reinforce the idea that pressure anisotropies-driven naturally in a turbulent collisionless medium, e.g., the intergalactic medium, could efficiently amplify the magnetic field in the early universe (post-recombination era), previous to the collapse of the first large-scale gravitational structures. This mechanism, though fast for the small-scale fields (similar to kpc scales), is unable to provide relatively strong magnetic fields at large scales. Other mechanisms that were not accounted for. here (e.g., collisional turbulence once instabilities are quenched, velocity shear, or gravitationally induced inflows of gas into galaxies and clusters) could operate afterward. to build up large-scale coherent field structures in the long time evolution. (AU)

• Processo FAPESP: 13/18815-0 - Reconexão magnética e processos relacionados em plasmas astrofísicos colisionais e acolisionais: das chamas solares para fontes extragaláticas
• Beneficiário: Grzegorz Kowal
• Linha de fomento: Bolsas no Brasil - Apoio a Jovens Pesquisadores
• 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
• Linha de fomento: Auxílio à Pesquisa - Temático
• Processo FAPESP: 13/04073-2 - Reconexão magnética e processos relacionados em plasmas astrofísicos colisionais e acolisionais: das chamas solares para fontes extragaláticas
• Beneficiário: Grzegorz Kowal
• Linha de fomento: Auxílio à Pesquisa - Apoio a Jovens Pesquisadores