Flocculent flows in the chromospheric canopy of a sunspot

Дата и время публикации : 2012-02-24T14:05:55Z

Авторы публикации и институты :
Gregal Vissers
Luc Rouppe van der Voort

Ссылка на журнал-издание: The Astrophysical Journal (2012), 750, 22
Коментарии к cтатье: Accepted for publication in the Astrophysical Journal. 13 pages, 10 figures, see http://folk.uio.no/gregal/onlinematerial/flocflows for the accompanying movie
Первичная категория: astro-ph.SR

Все категории : astro-ph.SR

Краткий обзор статьи: High-quality imaging spectroscopy in the H{alpha} line, obtained with the CRisp Imaging SpectroPolarimeter (CRISP) at the Swedish 1-m Solar Telescope (SST) at La Palma and covering a small sunspot and its surroundings, are studied. They exhibit ubiquitous flows both along fibrils making up the chromospheric canopy away from the spot and in the superpenumbra. We term these flows "flocculent" to describe their intermittent character, that is morphologically reminiscent of coronal rain. The flocculent flows are investigated further in order to determine their dynamic and morphological properties. For the measurement of their characteristic velocities, accelerations and sizes, we employ a new versatile analysis tool, the CRisp SPectral EXplorer (CRISPEX), which we describe in detail. Absolute velocities on the order of 7.2-82.4 km/s are found, with an average value of 36.5pm5.9 km/s and slightly higher typical velocities for features moving towards the sunspot than away. These velocities are much higher than those determined from the shift of the line core, which shows patches around the sunspot with velocity enhancements of up to 10-15 km/s (both red- and blueshifted). Accelerations are determined for a subsample of features, that show clear accelerating or decelerating behavior, yielding an average of 270pm63 m/s^2 and 149pm63 m/s^2 for accelerating and decelerating features, respectively. Typical flocculent features measure 627pm44 km in length and 304pm30 km in width. On average 68 features are detected per minute, with an average lifetime of 67.7pm8.8 s. The dynamics and phenomenology of the flocculent flows suggest they may be driven by a siphon flow, where the flocculence could arise from a density perturbation close to one of the footpoints or along the loop structure.

Category: Physics