INAF Capodimonte Astronomical Observatory, Italy
Natural Sciences (Astrophysics and Astrononmy)
The Dark Halos (DHs) are regions of reduced emission in the neighborhood of solar active regions (ARs). Since their discovery (Hale & Ellerman, 1903), DHs have been called with various names, the first one being circumfacules (Deslanders, 1930), as they were first identified in the chromosphere as faint areas surrounding plages in the Ca II K-line, and later also in the Ca II 8542 Å line (D’Azumbuja, 1930). Bumba & Howard (1965) proposed that the Ca II circumfacules are composed of dark features corresponding to dark Hα fibrils, and this suggestion was supported by different authors (e.g. Rutten et al. 2007, Pietarila et al. 2009). Read more at https://espos.stream/2023/02/16/Lezzi/.
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