A dynamic magnetic tension force as the cause of failed solar eruptions

• Autores: Clayton E Myers, Masaaki Yamada, Hantao Ji, Jongsoo Yoo, William Fox, Jonathan Jara-Almonte, Antonia Savcheva, E.E. DeLuca
• Localización: Nature: International weekly journal of science, ISSN 0028-0836, Vol. 528, Nº 7583, 2015, págs. 526-529
• Idioma: inglés
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• Resumen

  • Coronal mass ejections are solar eruptions driven by a sudden release of magnetic energy stored in the Sun's corona1. In many cases, this magnetic energy is stored in long-lived, arched structures called magnetic flux ropes2-5. When a flux rope destabilizes, it can either erupt and produce a coronal mass ejection or fail and collapse back towards the Sun6-8. The prevailing belief is that the outcome of a given event is determined by a magnetohydrodynamic force imbalance called the torus instability9-14. This belief is challenged, however, by observations indicating that torus-unstable flux ropes sometimes fail to erupt15. This contradiction has not yet been resolved because of a lack of coronal magnetic field measurements and the limitations of idealized numerical modelling. Here we report the results of a laboratory experiment16 that reveal a previously unknown eruption criterion below which torus-unstable flux ropes fail to erupt. We find that such ‘failed torus’ events occur when the guide magnetic field (that is, the ambient field that runs toroidally along the flux rope) is strong enough to prevent the flux rope from kinking. Under these conditions, the guide field interacts with electric currents in the flux rope to produce a dynamic toroidal field tension force that halts the eruption. This magnetic tension force is missing from existing eruption models, which is why such models cannot explain or predict failed torus events.