1. DOT tomography of the solar atmosphere Leenaarts, J. and Wedenmeyer-Böhm, S. 2005 A&A 431, 681 Comments on the optimization of high resolution Fabry-Pérot filtergraphs Sharmer, G. B. 2006 A&A 447, 1111 Speaker: S. Kamio Solar Seminar 2006.02.27

2. Dutch open telescope 45cm diameter with open design High resolution (0.2") image by Speckle reconstruction Ongoing projects  BBSO/NST(1.6m), GREGOR(1.5m), ATST(4m), DOT++(1.4m)

3. G-band image bright points in the intergranular lanes  magnetic flux Movies available at http://dot.astro.uu.nl/ (79" x 63")

4. Reversed granulation dark intergranular-lane (G-band) bright cell-boundary (Ca II H)

5. Simulations CO 5 BOLD code (Wedenmeyer 2003) radiation + hydrodynamics non-magnetic 140x140x200 grids Synthesize Ca II H spectra with SPANSAT (396.0-396.8nm) blue continuum (396.0nm) in stead of G-band 5600km 1400km 1710km photosphere

6. Results simulation reproduces actual contrast Not all dark intergranular lanes show bright in Ca II H blue continuum Ca II H core Obs Calc Calc + smear

7. Brightness distribution solid curves are derived from simulations. solid curve 2 (smear with realistic Airy function) is close to the observation

8. Fourior analysis Phase difference G-band -- Ca II H Power spectra in good agreement Obs Simulation

9. Conclusions High resolution G-band and Ca II H images were obtained with DOT Results of non-magnetic hydrodynamics simulations agree well with observations Reversed granulation (i.e. dark intergranular lane and Ca II H brightening) can be explained by non-magnetic process

10. Fabry-Pérot interferometer (FPI) Basic parameters Reflectivity: R and cavity distance: d Benefit high transmission, rapid tuning, no-polarization, spectral resolution 2x10 5 Shortcomings Telecentric optics, wings of transmission profile R

11. FPI systems VTT/TESOS (Kentischer et al. 1998) Triple FPI THEMIS/IPM (Cavallini 1998) UBF + FPI THEMIS/IBS (Cavallini et al. 2003) dual FPI IMAX/SUNRISE (Martinez-Pillet 2004) ATST ?

12. Calculation 2 FPI system Parameters: d 1, d 2, R 1, and R 2 Estimate parasitic light, ghost intensity, and FWHM Cavity error < 2 nm d1d1 d2d2 R1R1 R2R2

13. Paracitic light level R=83% R=89% R=94%

14. Results Item

15. Conclusion Cavity ratio has a significant impact on FPI system performance Homogeneity can be achieved by lowering reflectivity of small cavity FPI Optimal setup Low resolution & low reflectivity + high resolution & high reflectivity (cavity ratio 0.3-0.4)

16. Template Item