Stabilizing Effect of Magnetic Helicity on Magnetic Cavities in the Intergalactic Medium

Simon Candelaresi, Fabio Del Sordo

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Abstract

We investigate the effect of magnetic helicity on the stability of buoyant magnetic cavities as found in the intergalactic medium. In these cavities we insert helical magnetic fields and test whether or not helicity can increase their stability to shredding through the Kelvin-Helmholtz instability and, with that, their lifetime. This is compared to the case of an external vertical magnetic field that is known to reduce the growth rate of the Kelvin-Helmholtz instability. By comparing a low-helicity configuration with a high-helicity one with the same magnetic energy, we find that an internal helical magnetic field stabilizes the cavity. This effect increases as we increase the helicity content. Stabilizing the cavity with an external magnetic field requires instead a significantly stronger field at higher magnetic energy. We conclude that the presence of helical magnetic fields is a viable mechanism to explain the stability of intergalactic cavities on timescales longer than 100 Myr.

Original languageEnglish
Article number86
Pages (from-to)1-9
Number of pages9
JournalAstrophysical Journal
Volume896
Issue number1
Early online date10 Jun 2020
DOIs
Publication statusPublished - 16 Jun 2020

Keywords

  • Warm-hot intergalactic medium
  • Magnetic fields

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