III. Long fibrils in Lyman-alpha and with ALMA
1 Lingezicht Astrophysics, ’t Oosteneind 9, 4158 CA Deil, The Netherlands
2 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, 181-8588 Tokyo, Japan
Received: 4 July 2016
Accepted: 4 October 2016
In H-alpha most of the solar surface is covered by dense canopies of long opaque fibrils, but predictions for quiet-Sun observations with ALMA have ignored this fact. Comparison with Ly-alpha suggests that the extraordinary opacity of H-alpha fibrils is caused by hot precursor events. Application of a recipe that assumes momentary Saha-Boltzmann extinction during their hot onset to millimeter wavelengths suggests that ALMA will observe H-alpha-like fibril canopies, not acoustic shocks underneath, and will yield data more interesting than if these canopies were transparent.
Key words: Sun: chromosphere / Sun: infrared
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