Standing kink modes in three-dimensional coronal loops

Ineke De Moortel, David James Pascoe

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)
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Abstract

So far, the straight flux tube model proposed by Edwin & Roberts is the most commonly used tool in practical coronal seismology, in particular, to infer values of the (coronal) magnetic field from observed, standing kink mode oscillations. In this paper, we compare the period predicted by this basic model with three-dimensional (3D) numerical simulations of standing kink mode oscillations, as the period is a crucial parameter in the seismological inversion to determine the magnetic field. We perform numerical simulations of standing kink modes in both straight and curved 3D coronal loops and consider excitation by internal and external drivers. The period of oscillation for the displacement of dense coronal loops is determined by the loop length and the kink speed, in agreement with the estimate based on analytical theory for straight flux tubes. For curved coronal loops embedded in a magnetic arcade and excited by an external driver, a secondary mode with a period determined by the loop length and external Alfvén speed is also present. When a low number of oscillations is considered, these two periods can result in a single, non-resolved (broad) peak in the power spectrum, particularly for low values of the density contrast for which the two periods will be relatively similar. In that case (and for this particular geometry), the presence of this additional mode would lead to ambiguous seismological estimates of the magnetic field strength.
Original languageEnglish
Article number101
Number of pages7
JournalAstrophysical Journal
Volume784
DOIs
Publication statusPublished - 11 Mar 2014

Keywords

  • Magnetohydrodynamics (MHD)
  • Sun: atmosphere
  • Sun: corona
  • Sun: magnetic fields
  • Sun: oscillations
  • Waves

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