The properties of penumbral grains (PGs) in a medium-size sunspot are studied from a 4.5 hour observation series acquired on 5 June 1993 at the Swedish Vacuum Solar Telescope, La Palma. The application of an image segmentation procedure and a feature tracking algorithm on a movie of 360 frames yields proper motions, intensities, and lifetimes for a set of 469 PGs. Almost 3/4 of the PGs move tow...

Context. The sunspot umbra harbours the coolest plasma on solar surface due to presence of strong magnetic fields. atomic lines that are routinely used observe photosphere have weak signals in and often swamped by molecular lines. This makes it harder infer properties umbra, especially darkest regions.

Nesse artigo, o poema em prosa "Umbra”, de João da Cruz e Sousa (2008 [1891]), é tomado como epítome do espaço urbano derruído, reportando-o a Charles Baudelaire ao pós-simbolista “Sub-umbra”, Artur Sales (1987 [1950]), enunciação estranhamento saturnino (Giorgio Agamben) renúncia (Paul Valéry) justaposição conceito “fugacidade eterna” (BENJAMIN, 2006). Nessa dialética, imagem afloramento calcá...

A solar eclipse is a rare but spectacular natural phenomenon and furthermore it is a challenge for radiative transfer modelling. Whereas a simple one-dimensional radiative transfer model with reduced solar irradiance at the top of the atmosphere can be used to calculate the brightness during partial eclipses a much more sophisticated model is required to calculate the brightness (i.e. the diffu...

Generating soft shadows in real-time is difficult. Exact methods (such as ray tracing, and multiple light source simulation) are too slow, while approximate methods often over-estimate the umbra regions. In this paper, we introduce a new algorithm based on the shadow map method to quickly and accurately render soft shadows produced by a light source. Our method builds inner and outer translucen...

Context. It is unclear why there a rather sharp boundary in sunspots between the umbra and penumbra. Both regions exhibit magnetoconvection, which manifests penumbral filaments penumbra umbral dots umbra. Aims. Here we compare physical properties of filaments. Our goal to understand how these convective features change across this related rapid increase brightness at umbra-penumbra boundary. Me...

Image segmentation involves calculating the position of object boundaries. For scene analysis, the intent is to di erentiate objects from clutter by means of preprocessing. The objective of this paper is to examine and discuss two morphological techniques for preprocessing and segmenting range images. A MorphologicalWatershed Algorithm has been studied in detail for segmenting range images. Thi...

High-resolution imaging observations from the Hinode spacecraft in the Ca II H line are employed to study the dynamics of the chromosphere above a sunspot. We find that umbral flashes and other brightenings produced by the oscillation are extremely rich in fine structure, even beyond the resolving limit of our observations (0.22”). The umbra is tremendously dynamic, to the point that our time c...

The Solar Optical Telescope (SOT) aboardHINODE successfully and continuously observed a formation process of a light bridge in a matured sunspot of the NOAA active region 10923 for several days with high spatial resolution. During its formation, many umbral dots were observed emerging from the leading edges of penumbral filaments, and intruding into the umbra rapidly. The precursor of the light...