Solar Physics with a Night-Time Instrument

1. Solar Physics with a Night-Time Instrument Carsten Denker Astrophysical Institute Potsdam Solar Observatory Einstein Tower PEPSI Team: K.G. Strassmeier, M. Woche, I. Ilyin, E. Popow, S.-M. Bauer, F. Dionies, T. Fechner, M. Weber, A. Hofmann, J. Storm, R. Materne, W. Bittner, J. Bartus, T. Granzer, T. Carroll, M. Kopf, I. DiVarano, E. Beckert and M. Lesser

2. Introduction • When Solar Physicists use Night-Time Instruments … • Solar Disk Integrated (SDI) Telescope • Mount • Optical Design • Extinction Monitor • Comparison with other solar instruments • SDI Science • Data management • What’s wrong with the Sun? Second Generation Science with LBT

3. When Solar Physicists use Night-Time Instruments … Second Generation Science with LBT

4. Instrument Characteristics • Sun-as-a-Star telescope, which ties into PEPSI calibration unit via an optical fiber (no polarimetry!) • External calibration source for PEPSI ultra-high-resolution (UHR) mode • Monitor instrument profile and long-term stability • Operation for one Solar Cycle • Spectral resolution: 310,000 (resolve telluric spectral lines  remove line blends) • Spectral range: 390–1065 nm (covered in 2 × 3 exposures) • Kitt Peak Fourier Transform Spectrometer (predominantly for IR observations: CO, CO2, NO2, O2, water vapor, … & spectral atlas) • SOLIS Integrated SunlightSpectrometer (ISS)  SDI higher S/N and continuous spectral coverage Second Generation Science with LBT

5. Alt-azimuth mount (SPTRV5 tracking system from Dr. Schulz+Partner) in an environmentally protected box SDI located on the LBTO kitchen balcony Four-quadrant cell with 8° for solar disk acquisition and guiding 0.02° (72″) positioning accuracy Telescope aperture: 13 mm, f /13 achromat The pupil of a solar-certified eyepiece is used to feed a 300µm fiber STELLA control system Commissioning with sunlight (PEPSI/SDI) Q2 2010 SDI Telescope & Mount Second Generation Science with LBT

6. Location, location, location, … Second Generation Science with LBT

7. Overall Fiber-Feed Concept Second Generation Science with LBT

8. SDI Optical Fiber Path Second Generation Science with LBT

9. SDI Optical Design Second Generation Science with LBT

10. Extinction Monitor • Monitor extinction gradients across the solar disk • Gradients can lead to unexpected weighting and thus influence the interpretation of spectral features (shape and line strength) • Five full-disk images to derive wavelength dependence (interference filters with 10 nm bandpass) • Images (100 pixel across) are captured simultaneously (wedge steering prisms) with the same CCD camera • 15 Hz data acquisition • Software monitors gradients and overall intensity level • Information will be stored in a database Second Generation Science with LBT

11. NOAA 10892 SOLIS Context Data Second Generation Science with LBT

12. SOLIS ISS Data Second Generation Science with LBT

13. Compare high-resolution spectra with solar-full disk observations from photosphere to corona Precision Solar Photometric Telescope (PSPT) Global Hα Network Solar TErrestrial RElations Observatory (STEREO) Solar Dynamics Observatory (SDO) to be launched December 2008 Full-Disk Proxy Magnetometry Second Generation Science with LBT

14. The Sun at High Spatial Resolution Second Generation Science with LBT

15. SDI Science • Measure line-bisector curvatures and variations over an entire activity cycle (signature of convection) • Solar cycle related irradiance changes • Strong response of Ca II H & K to magnetic activity (20+ year data base at NSO and other observatories – Mt. Wilson program for solar-type stars) • Strong correlation between Ca II K and luminosity variations • Rotational modulation of spectra in the presence of sunspots and plages • Spectral lines of interest: CN λ388.3 nm, Ca K λ393.3 nm, Ca H λ396.8 nm, C Iλ538.0 nm, Mn Iλ539.4 nm, Hαλ656.3 nm, O Iλ777.4 nm and Ca IIλ854.2 nm • Magnetic fields  subtle effects of Zeeman broadening in absorption line wings • Special observing modes with only one cross-disperser setting for helioseismology (1-min cadence with S/N of 1000:1 to resolve 5-min oscillation) Second Generation Science with LBT

16. Synoptic Solar Science • Network of synoptic telescopes (recommended for SOLIS by NSF AST senior review and decadal survey) • Evolution of the 3D magnetic field over the 11-year activity cycle  long-term (25-year project) • Causes of the solar cycle? • Eruptive events: flares and coronal mass ejections • How is energy stored and released in the solar atmosphere? (time scales ≈ minutes, spatial scale Mm) • Space weather predictions and forecasts • Solar-stellar connection  stellar flares Second Generation Science with LBT

17. Data Management • Single 2 s exposure (200 MB)  S/N ≈ 500:1 • 100 exposures (20 GB)  S/N ≈ 5000:1 • 6 cross-disperser (CD) settings (blue & red arm) • 12+1 s read-out time per frame  3 × 25 min = 1.25 h data acquisition (4–6 data sets per day) • Raw data flow is about 500 GB/day • Total archive need would be 120 TB/year!!! • 1D spectrum = 340 kB per CD setting  2 MB full PEPSI spectrum  2 GB/day for all 1D spectra • (6+2) × 200 MB co-added raw frames  1.6 GB/day • Total: 4 GB/day (2 GB/day with loss-less compression) • TOTAL: 1–2 TB (or hard drives) per year • Web-based access to data archive (Virtual Solar Observatory): a few full 1D spectra per day (storage requirements negligible) Second Generation Science with LBT

18. What's Wrong with the Sun? • The Sunspot Enigma: The Sun is “Dead”—What Does it Mean for Earth? • The Sunspot Enigma: The Sun Seems Eerily Calm • Could a new sunspot drought plunge us into another decades-long cold spell? • Still no sunspots ... • Where are the Sunspots? Are we in for a Quiet Solar Cycle? • Unusual Absence of Sunspots Sparks Climate Concerns Second Generation Science with LBT