Quiet-Sun chromospheric mottles         

Swedish 1-m Solar Telescope

When observed in the H-alpha spectral line, the chromosphere reveals a very complex structure made up of elongated fibrils having different lengths and orientations. They are believed to trace magnetic field lines in the chromosphere. Above active regions there are long, horizontal fibrils that connect sunspots or plage of opposity polarity. We can also see dynamic fibrils, which are shorter, more vertical and much more dynamical. In the quiet Sun, fibrils are observed at the boundaries of network element, forming rosettes of long dark elongated structures called mottles.

This movie shows a spectral scan of the quiet Sun across the H-alpha line. Positions in the far line wings sample the photosphere. Toward the line core, the images sample progressively higher layers of the atmosphere, up to the upper chromosphere.

The far-wing intensity images show the typical granulation pattern of the quiet Sun, with areas of concentrated magnetic bright points representing the photospheric network. These are the centers of chromospheric rosettes, well visible in H-alpha line core intensity. There are three such rosettes in the field of view, two on the left (at the very bottom and at mid height) and one on the right (at mid height). They can be recognized by the long dark fibrils emanating from their centers - the mottles.

To download the movie, click HERE

Movie credit: Luc Rouppe van der Voort (ITA, University of Oslo)

Text credit: Luis Bellot Rubio (IAA-CSIC)

Source: SST Galleries