Modelling the global solar corona II: Coronal evolution and filament chirality comparison

A. R. Yeates, D. H. Mackay, A. A. van Ballegooijen

Research output: Contribution to journalArticlepeer-review

87 Citations (Scopus)

Abstract

This paper considers the hemispheric pattern of solar filaments using newly developed simulations of the real photospheric and 3D coronal magnetic fields over a six-month period, on a global scale. The magnetic field direction in the simulation is compared directly with the chirality of observed filaments, at their observed locations. In our model the coronal field evolves through a continuous sequence of nonlinear force-free equilibria, in response to the changing photospheric boundary conditions and the emergence of new magnetic flux. In total 119 magnetic bipoles with properties matching observed active regions are inserted. These bipoles emerge twisted and inject magnetic helicity into the solar atmosphere. When we choose the sign of this active-region helicity to match that observed in each hemisphere, the model produces the correct chirality for up to 96% of filaments, including exceptions to the hemispheric pattern. If the emerging bipoles have zero helicity, or helicity of the opposite sign, then this percentage is much reduced. In addition, the simulation produces a higher proportion of filaments with the correct chirality after longer times. This indicates that a key element in the evolution of the coronal field is its long-term memory, and the build-up and transport of helicity from low to high latitudes over many months. It highlights the importance of continuous evolution of the coronal field, rather than independent extrapolations at different times. This has significant consequences for future modelling such as that related to the origin and development of coronal mass ejections.

Original languageEnglish
Pages (from-to)103-121
Number of pages19
JournalSolar Physics
Volume247
Issue number1
DOIs
Publication statusPublished - Jan 2008

Keywords

  • magnetic fields
  • corona
  • prominences
  • magnetic field
  • helicity
  • magnetic
  • FREE MAGNETIC-FIELDS
  • LARGE-SCALE CORONA
  • FORCE-FREE
  • HEMISPHERIC PATTERN
  • MASS EJECTIONS
  • FLUX ROPES
  • PROMINENCES
  • HELICITY
  • CHANNELS
  • SUN

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