Physics
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufmsh23b0359d&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #SH23B-0359
Physics
7507 Chromosphere, 7524 Magnetic Fields, 7529 Photosphere
Scientific paper
With the recent advent of the Swedish 1-m Solar Telescope (SST), advanced image processing techniques, as well as numerical simulations that provide a more realistic view of the chromosphere, a comprehensive understanding of chromospheric jets such as spicules, mottles and fibrils is now within reach. We will present results from a recent analysis of dynamic fibrils, short-lived jet-like features that dominate the chromosphere (as imaged in Hα) above and about active region plage. These jets are similar to mottles and spicules in quiet Sun. Our analysis is based on a time series of extremely high-resolution (120 km) images taken in Hα linecenter at 1 second cadence, obtained by the Oslo group at the SST in October 2005. The 78 min long time series for the first time, spatially and temporally resolves dynamic fibrils in active regions. Our analysis shows that most of the fibrils follow almost perfect parabolic paths in their ascent and descent. We measure the properties of the parabolic paths taken by 257 different dynamic fibrils, and find that the observed deceleration of the projected path is typically only a fraction of solar gravity, and incompatible with a ballistic path at solar gravity. We report on significant differences of measured fibril properties between those occurring in association with a dense plage region, and those above a less dense plage region where the magnetic field seems more inclined away from the vertical. We compare these observational findings to advanced numerical 2D radiative MHD simulations, and find that fibrils are most likely formed by chromospheric shock waves that occur when convective flows and global oscillations leak into the chromosphere along the field lines of magnetic flux concentrations. Detailed comparison of the properties of fibrils found in our observations and those in our numerical simulations shows striking similarities of the values for deceleration, maximum velocity, maximum length and duration. The numerical simulations also reproduce the correlations we observe between various fibrils properties, as well as the regional differences, taking into account the different magnetic configuration for the various regions. We compare our results with observations of mottles and find that a similar mechanism is most likely at work in the quiet Sun.
Carlsson Marcus
de Pontieu Bart
der Voort Luc Rouppe van
Hansteen Viggo H.
van Noort Michiel
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