K-grains as a three-dimensional phenomenon. I. Statistics and spatial evolution.
Abstract
We present new data concerning the statistics and motion of chromospheric K-grains, in order to verify possible excitation mechanisms. We have analysed a time-series of Ca K_2v_ filtergrams obtained with the VTT at Observatorio del Teide, Tenerife. K-grains are not only characterised by their brightness but also by their pointlike appearance and in some cases by a horizontal motion. Our statistical analysis of the spatial distribution of bright point emission reveals no significant clustering at particular areas in the internetwork. Some of the observed grains travel through the chromospheric internetwork cells with a speed comparable to the phase speed of the solar p-modes. Both results seem to be inconsistent with a causal relation between Ca K bright points and magnetic flux tubes, and rather favour a mechanism related to p-mode interference. Finally we present statistical evidence showing that bright points do not dominate the emission of the quiet chromosphere but rather contribute only about 9 percent of the K_2v_ intensity emitted from the internetwork areas in our data.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- March 1996
- Bibcode:
- 1996A&A...307..288S
- Keywords:
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- SUN: CHROMOSPHERE;
- SUN: OSCILLATIONS