Horizontal motions in sunspot penumbrae

0558170 - ASÚ 2023 RIV FR eng J - Journal Article
Sobotka, Michal - Puschmann, K.G.
Horizontal motions in sunspot penumbrae.
Astronomy & Astrophysics. Roč. 662, May (2022), č. článku A13. ISSN 0004-6361. E-ISSN 1432-0746
Institutional support: RVO:67985815
Keywords : Sun * photosphere * sunspots
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 6.5, year: 2022
Method of publishing: Open access

A model of penumbral filaments represented by magnetoconvective cells was derived recently from spectropolarimetric observations. High-resolution observations of horizontal motions in the penumbra are needed to complement the concept of penumbrae obtained from spectropolarimetry. Time series of images of a large sunspot acquired with the Swedish Solar Telescope are analysed. Horizontal motions of penumbral grains (PGs), structures in dark bodies of filaments, the outer penumbral border, and G-band bright points are measured in time slices. In the inner penumbra, PGs move towards the umbra (inwards) with a mean speed of -0.7 km/s. The direction of motion changes from inwards to outwards at approximately 60% of the penumbral width, and the mean speed increases gradually in the outer penumbra, approaching 0.5 km/s. This speed is also typical of an expansion of the penumbra–granulation border. The majority of the G-band bright points moves away from the sunspot, with a typical speed of 0.6 km/s. High outward speeds, 3.6 km/s on average, are observed in dark bodies of penumbral filaments. According to the model of penumbral filaments, it is suggested that the speeds detected in the dark bodies of filaments are associated with the Evershed flow and that the opposite directions of PG motions in the inner and outer penumbrae may be explained by the interaction of rising plasma in filament heads with a surrounding, differently inclined magnetic field.

Permanent Link: http://hdl.handle.net/11104/0332249