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SOLIS-VSM Magnetic Synoptic Maps C.J. Henney

Learn about the SOLIS-VSM instrument operating on Kitt Peak, its magnetic synoptic maps, and a comparison with the KPVT telescope. Explore the process of creating synoptic maps and upcoming developments in data products.

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SOLIS-VSM Magnetic Synoptic Maps C.J. Henney

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  1. SOLIS-VSM Magnetic Synoptic Maps C.J. Henney

  2. Instrument Overview KPST • Currently the SOLIS mount, Integrated Sunlight Spectrometer (ISS) and Vector SpectroMagnetograph (VSM) are operating on Kitt Peak. • Full-Disk Patrol (FDP) in Tucson: • being used for guider development VSM ISS FDP (Status: nominal; installed at KPST) (Status: need to complete final optical alignment) (status: need to install guider)

  3. VSM Basics • The 50-cm aperture VSM utilizes a Ritchey-Chrétien optical design. • Full-disk parametergrams are constructed from 2048 individual steps in declination of the projected solar image on the entrance slit. • The observed spectrum lines would be curved due to the relatively large angular deviation of 0.57 degrees in the spectrograph. However, the slit is curved to compensate for the curvature. • The VSM utilizes two interim CMOS hybrid cameras made by Rockwell Scientific.

  4. KPVT & SOLIS Transition KPVT • The Kitt Peak Vacuum Telescope (KPVT) operated between Sep 1973 until Sep 2003 • Synoptic maps: CR 1625 - 2007 • The SOLIS-VSM began taking daily full-disk observations in August 2003. • Synoptic maps: CR 2007 – present • During Aug/Sep 2003, the KPVT & VSM operated jointly. • The VSM was installed at Kitt Peak in May 2004; KPVT was renamed to SOLIS Tower (KPST). KPST

  5. KPVT & VSM Comparison KPVT Photospheric longitudinal magnetograms: KPVT VSM VSM (Images from August 23, 2003)

  6. Example VSM LOS Magnetogram AR 10808 AR 10810 VSM observation from September 20, 2005 at 15:47 UT (grayscale: +/-150 Mx/cm2)

  7. Example VSM LOS Magnetogram VSM observation from September 20, 2005 at 15:47 UT (grayscale: +/-25 Mx/cm2)

  8. Example VSM LOS Magnetogram VSM observation from September 20, 2005 at 15:47 UT (grayscale: +/-5 Mx/cm2)

  9. Example VSM LOS Magnetogram VSM obs from September 20, 2005 at 15:47 UT (grayscale: +/-5 Mx/cm2)

  10. Example Map: CR 2029

  11. Synoptic Map Recipe Steps from full-disk data to synoptic map are: • Apply zero point correction: • Stable (dependent on modulator package) • Apply geometric corrections: • Slit curvature correction, p-angle • Estimate limb and disk center • Map into Carrington frame (sine-lat, CMD): • 2 resolutions: 180x180 and 900x900 [pixels] • 3 maps: net flux, total flux, and the spatial weighting • Flux conserved (using KPVT code)

  12. 4. Pole Estimation • Steps to fill data gaps at the poles: • For each pole with missing data, the pole-ward rows of the synoptic map are split at 180 deg and the opposing longitudes are aligned for each pole (i.e. rotating the 180 to 360 deg longitude columns by 180 degrees). • Remove any data spikes with median filter along each row of the new polar region array. Also, smooth along each row. • Fit across data gaps at each pole: • Spline fit (to match data) • Least abs deviation (LAD) fit (to match local trend) • Combine fits with inverse distance weighting (weights are clipped at 0.5 if gap has fewer than 5 pixels): wt*Splinefit + (1. - wt)*Ladfit • Median filter & smooth rows while increasing the window width towards the pole (pad edges with columns separated by 360 deg).

  13. VSM Synoptic Maps Net Flux Frame (CR 2009) • Current magnetic synoptic FITS files • include 3 frames (sine-lat vs. long): • net flux [Mx/cm2] • total flux [Mx/cm2] • spatial weighting: • cos4(cmd) for 180x180 • wt pixels set to -1 where unobserved polar regions are filled with values Total Flux Frame Weights for filled values set to -1 Spatial Weight Frame cos4(cmd) weighting (see Harvey & Worden 1998; Harvey et al. 1980)

  14. New Data Products: Ca II 854.2 nm 854.2 nm Line-core field (new algorithm) 854.2 nm Line-wing field (new algorithm) 630.2 nm photospheric 854.2 nm Line-core field (KPVT algorithm)

  15. Sample VSM Stokes Profiles Example Stokes profile fits using EHF (Expansion in Hermite Functions)

  16. Photospheric Vector Info: QL example (from 3/2/2007)

  17. Summary • Finalizing the processing of Fe I 630.25 nm magnetograms. This line has greater sensitivity, plus “simpler” spectra in umbral regions, than Fe I 630.15 nm. The 630.25 full-disk magnetograms and synoptic maps will replace the currently available photospheric data. • Further development is needed with regards to the VSM zero-point & geometry correction. • Plan to create Ca II 854.2 nm photospheric and chromospheric synoptic maps. • In addition, need to “finalize” synoptic map pole estimation algorithm. • Plan to include active region fields determined from photospheric vector magnetograms in synoptic maps.

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