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Astron. Astrophys. 360, 1157-1162 (2000)

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4. Conclusion

We have shown above (and in Paper I) that high spatial resolution spectroscopy is possible by combining speckle reconstruction with two-dimensional narrow-band imaging. This allows to study the dynamics of the fine structure of the solar atmosphere. High granular velocities and velocity differences are seen at small scales. A turbulent decay of the granulation, either of intensity or of velocity, i.e. a decrease of log(power) vs. log(wavenumber) with -5/3 or -17/3 could only roughly be confirmed from our high spatial resolution data. Coherence and phase difference of intensity and velocity fluctuations indicate convective motions down to scales of 0:005.

The results are encouraging and further investigations with the same or with better resolution are to follow. The analysis of time sequences will allow the proper separation of granular motions from evanescent (5-min period) and short period waves. This will give insight into the temporal evolution of both granular dynamics and waves at small structural lengths. Smaller bandwidths in wavelength than used here will lead to a better discrimination of the height ranges from which the signals stem. And finally, studies of structures with sizes smaller than 0:002-0:004 need more photons from telescopes with larger aperture than the VTT on Tenerife.

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© European Southern Observatory (ESO) 2000

Online publication: August 23, 2000