activity
20172025
most citedThe magnetic nature of umbra-penumbra boundary in sunspots

44 citations · 93 across the 8 of their papers we have counts for

collaborators

8 papers

astro-ph.SR2025★ 5 cited

Average solar active region: I. Intensities, velocities, and the photospheric magnetic field

M. Švanda, J. Jurčák, M. Schmassmann

Context: Solar active regions (ARs) are key manifestations of the Sun's magnetic activity, displaying diverse spatial and temporal characteristics. Their formation and evolution pl…

astro-ph.SR2024

Magnetic properties of the umbral boundary during sunspot decay. Comparative study of multiple datasets

M. García-Rivas, J. Jurčák, N. Bello González

The magnetic properties of the umbra-penumbra (UP) boundary of sunspots and the boundary of pores at various evolutionary stages have been characterised using datasets from differe…

astro-ph.SR2024★ 7 cited

Onset of penumbra formation

M. García-Rivas, J. Jurčák, N. Bello González +3

Context. Fully fledged penumbrae have been widely studied both observationally and theoretically. Yet the relatively fast process of penumbra formation has not been studied closely…

astro-ph.SR2023

Relation between magnetic field inclination and apparent motion of penumbral grains

Michal Sobotka, Jan Jurčák, J. Sebastián Castellanos Durán +1

Context. Bright heads of penumbral filaments, penumbral grains (PGs), show apparent horizontal motions inwards, towards the umbra, or outwards, away from the umbra. Aims. We aim to…

astro-ph.SR2020

Exploiting solar visible-range observations by inversion techniques: from flows in the solar subsurface to a flaring atmosphere

Michal Švanda, Jan Jurčák, David Korda +1

Observations of the Sun in the visible spectral range belong to standard measurements obtained by instruments both on the ground and in the space. Nowadays, both nearly continuous…

astro-ph.SR2019★ 6 cited

Science Requirement Document (SRD) for the European Solar Telescope (EST) (3rd Edition, December 2025)

Rolf Schlichenmaier, Luis R. Bellot Rubio, Manuel Collados Vera +31

The European Strategy Forum on Research Infrastructures (ESFRI) included the European Solar Telescope (EST) as an ESFRI Project in its 2016 Roadmap and confirmed this status in 202…

astro-ph.SR2018★ 44 cited

The magnetic nature of umbra-penumbra boundary in sunspots

Jan Jurčák, Reza Rezaei, Nazaret Bello González +2

Sunspots are the longest-known manifestation of solar activity, and their magnetic nature has been known for more than a century. Despite this, the boundary between umbrae and penu…

astro-ph.SR2017★ 31 cited

Normal and counter Evershed flows in the photospheric penumbra of a sunspot. SPINOR 2D inversions of Hinode-SOT/ SP observations

A. Siu-Tapia, A. Lagg, S. K. Solanki +2

Context. The Evershed effect, a nearly horizontal outflow of material seen in the penumbrae of sunspots in the photospheric layers, is a common characteristic of well-developed pen…