Bibcode
Felipe, T.; Khomenko, E.; Collados, M.; Beck, C.
Bibliographical reference
"12th European Solar Physics Meeting, Freiburg, Germany, held September, 8-12, 2008. Online at http://espm.kis.uni-freiburg.de/, p.2.12"
Advertised on:
9
2008
Citations
0
Refereed citations
0
Description
Observations in different spectral lines give us information about the
different layers of the solar atmosphere. Here we analyze the
propagation of waves in sunspots from the photosphere to the
chromosphere using time series of cospatial Ca II H intensity spectra
and polarimetric spectra of Si I 10827 A and He I 10830 A multiplet.
From the Doppler shifts of these lines we retrieve the temporal
variations of the velocity along the line-of-sight at several heights.
Phase spectra are used to get the relation between oscillatory signals
measured at each spectral signature. Our analysis reveals standing waves
for frequencies lower than 3.5 mHz and propagating waves for higher
frequencies, which steepen into shocks in the chromosphere. Oscillations
are detectable in Ca II H wings and they are propagated along line wing
layers to the line core. Ca II H core forms at a lower height than the
He I 10830 A line. A time delay of about 30 s is measured between the
Doppler signals detected at both wavelengths. We also find that in
"cold" sunspots the Si I 10827 A forms deeper than in the quiet sun.
This type of measurements demonstrate the importance of simultaneous
co-spatial observations at different wavelengths. Future
infrastructures, such as GREGOR and EST, should include multi-wavelength
capabilities to make possible the study of the photosphere-chromosphere
connection with the highest spatial and temporal resolution.