Small-scale magnetic flux emergence (2/2)

Swedish 1-m Solar Telescope

Magnetic flux emergence is the process in which the magnetic fields generated inside the Sun (below the surface) pierce the photosphere (the layer of the Sun from which most light comes from) and then rise and fill the Sun's outer atmosphere. Those magnetic fields are responsible for all the activity we see in the Sun.

The image shows an area of the solar surface where abundant magnetic flux was emerging vigorously on July 5, 2009. The observations were taken with the Crisp Imaging Spectropolarimeter at the Swedish 1-m Solar Telescope in a photospheric spectral line (Fe I 6301 A) and a chromospheric line (Ca II 8542 Å). The left panel shows continuum intensity at 6301 Å, the center panel is intensity in the blue wing of Ca II 8542 Å and the right panel is a map of mean circular polarization in the Fe I line (a sort of magnetogram). The red boxes outline two areas where small-scale magnetic flux was emerging into the solar surface.

Once the magnetic field has protruded into the surface of the Sun, the two opposite polarities (negative and positive, seen in the magnetogram as black and white patches respectively) separate from each other. At the same time a magnetic "bubble" (a large bubble of cool magnetised gas) travels upwards towards the higher layers of the solar atmosphere, filling the chromosphere, transition region and corona with the newly emerged field. In this way the Sun pumps new field into those higher layers eventually replacing older fields and interacting with them. This process is illustrated in the movie, which shows how the opposite polarities patches (in the shape of a half-moon) drift away from each other, and how a dark feature (the magnetic bubble) moves upwards.

Magnetic flux emergence is a complex process that knits together the interior of the Sun with the layers composing its outer atmosphere.

To download the movie, click HERE

Movie credit: Ada Ortiz (ITA, University of Oslo), Luis Bellot Rubio (IAA-CSIC)

Publication: Ortiz et al., 2014, The Astrophysical Journal, 781, 126