COMPARISON OF A GLOBAL MAGNETIC EVOLUTION MODEL WITH OBSERVATIONS OF CORONAL MASS EJECTIONS

A. R. Yeates, G. D. R. Attrill, Dibyendu Nandy, D. H. Mackay, P. C. H. Martens, A. A. van Ballegooijen

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)

Abstract

The relative importance of different initiation mechanisms for coronal mass ejections (CMEs) on the Sun is uncertain. One possible mechanism is the loss of equilibrium of coronal magnetic flux ropes formed gradually by large-scale surface motions. In this paper, the locations of flux rope ejections in a recently developed quasi-static global evolution model are compared with observed CME source locations over a 4.5 month period in 1999. Using extreme ultraviolet data, the low-coronal source locations are determined unambiguously for 98 out of 330 CMEs. An alternative method of determining the source locations using recorded Ha events was found to be too inaccurate. Despite the incomplete observations, positive correlation (with coefficient up to 0.49) is found between the distributions of observed and simulated ejections, but only when binned into periods of 1 month or longer. This binning timescale corresponds to the time interval at which magnetogram data are assimilated into the coronal simulations, and the correlation arises primarily from the large-scale surface magnetic field distribution; only a weak dependence is found on the magnetic helicity imparted to the emerging active regions. The simulations are limited in two main ways: they produce fewer ejections, and they do not reproduce the strong clustering of observed CME sources into active regions. Due to this clustering, the horizontal gradient of radial photospheric magnetic field is better correlated with the observed CME source distribution (coefficient 0.67). Our results suggest that while the gradual formation of magnetic flux ropes over weeks can account for many observed CMEs, especially at higher latitudes, there exists a second class of CMEs (at least half) for which dynamic active region flux emergence on shorter timescales must be the dominant factor. Improving our understanding of CME initiation in future will require both more comprehensive observations of CME source regions and more detailed magnetic field simulations.

Original languageEnglish
Pages (from-to)1238-1248
Number of pages11
JournalAstrophysical Journal
Volume709
Issue number2
DOIs
Publication statusPublished - 1 Feb 2010

Keywords

  • Sun: corona
  • Sun: coronal mass ejections (CMEs)
  • Sun: evolution
  • Sun: magnetic topology
  • SOLAR ACTIVE-REGION
  • FILAMENT CHANNELS
  • HEMISPHERIC PATTERN
  • NULL POINTS
  • FLUX ROPES
  • FIELDS
  • SUN
  • SIMULATIONS
  • PROMINENCES
  • CHIRALITY

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