Magnetic topology of solar prominences

Vacuum Tower Telescope

Solar prominences are seen as bright translucent clouds at the solar limb because they mainly scatter light from the underlying disc. These clouds form in regions of complex magnetic topology, which can evolve abruptly, disintegrating the prominence and ejecting magnetised material into the heliosphere. Interestingly for space weather predictions, 50% of solar tornadoes — a particular kind of prominence associated with apparently rotating, vertical, funnel-shaped dark structures — are eruptive and can have strong implications for the coronal magnetic field and the heliosphere.

The actual topology of the magnetic field is what maintains the tornado stable. When it erupts, the polarity of this field determines whether or not the ejected cloud of magnetised material will reconnect with the Earth’s magnetic fields inducing geomagnetic storms.

Spectro-polarimetric observations in the He I 1083 nm spectral line obtained with the Tenerife Infrared Polarimeter at the Vacuum Tower Telescope (Observatorio del Teide, Spain) revealed the three-dimensional topology of the magnetic field in a tornado prominence. Drawing the field lines obtained using the most sophisticated analysis tools to date, we can see that tornadoes harbour vertical, helical fields that connect the main body of the prominence with the underlying surface, in contrast to most of the theoretical predictions so far.

Image credit: María Jesús Martínez González (IAC)

Publication: Martínez González et al., 2015, ApJ 802, 3