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Speaker: S. Kamio Solar Seminar 2006.02.27

Discusses high-resolution solar imaging using DOT and Fabry-Pérot interferometers, simulations, brightness distribution, and conclusions on granulation phenomena. Details on FPI systems and parameters. Results on FPI performance impact and optimal setups.

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Speaker: S. Kamio Solar Seminar 2006.02.27

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  1. DOT tomography of the solar atmosphereLeenaarts, J. and Wedenmeyer-Böhm, S. 2005 A&A 431, 681Comments on the optimization of high resolution Fabry-Pérot filtergraphsSharmer, 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 (79" x 63") Movies available at http://dot.astro.uu.nl/

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

  5. Simulations • CO5BOLD code(Wedenmeyer 2003)radiation + hydrodynamicsnon-magnetic • 140x140x200 grids • Synthesize Ca II H spectrawith SPANSAT(396.0-396.8nm) • blue continuum (396.0nm)in stead of G-band 1710km photosphere 5600km 1400km 5600km

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

  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 differenceG-band -- Ca II H • Power spectrain 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 parametersReflectivity: R and cavity distance: d • Benefithigh transmission, rapid tuning, no-polarization,spectral resolution 2x105 • ShortcomingsTelecentric 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 R1 R2 • 2 FPI system • Parameters: d1, d2, R1, and R2 • Estimate parasitic light, ghost intensity, and FWHM • Cavity error < 2 nm d1 d2

  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 setupLow resolution & low reflectivity +high resolution & high reflectivity (cavity ratio 0.3-0.4)

  16. Template • Item

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