1. SOLIS-VSM Magnetic Synoptic Maps
C.J. Henney
Magnetogram Workshop, April 2007

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)
Magnetogram Workshop, April 2007

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.
Magnetogram Workshop, April 2007

4. KPVT & SOLIS Transition
The Kitt Peak Vacuum Telescope (KPVT) operated between Sep 1973 until Sep 2003
Synoptic maps: CR
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
Magnetogram Workshop, April 2007

5. KPVT & VSM Comparison Photospheric longitudinal magnetograms: KPVT VSM
Spectral
Line(s)
Fe I nm
FeI nm
FeI nm
Resolution
200,600
230,000
Pixel Size
~1.1 arcsec
Obs Time for Full-disk
45 minutes
12 minutes
Noise Level
~3 Mx/cm2
< 1 Mx/cm2
VSM
(Images from August 23, 2003)
Magnetogram Workshop, April 2007

6. Example VSM LOS Magnetogram
AR 10810
AR 10808
VSM observation from September 20, 2005 at 15:47 UT (grayscale: +/-150 Mx/cm2)
Magnetogram Workshop, April 2007

7. Example VSM LOS Magnetogram
VSM observation from September 20, 2005 at 15:47 UT (grayscale: +/-25 Mx/cm2)
Magnetogram Workshop, April 2007

8. Example VSM LOS Magnetogram
VSM observation from September 20, 2005 at 15:47 UT (grayscale: +/-5 Mx/cm2)
Magnetogram Workshop, April 2007

9. Example VSM LOS Magnetogram
VSM obs from September 20, 2005 at 15:47 UT (grayscale: +/-5 Mx/cm2)
Magnetogram Workshop, April 2007

10. Example Map: CR 2029
Magnetogram Workshop, April 2007

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)
Magnetogram Workshop, April 2007

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).
Magnetogram Workshop, April 2007

13. (see Harvey & Worden 1998; Harvey et al. 1980)
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)
Magnetogram Workshop, April 2007

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)
854.2 nm Line-core field (KPVT algorithm)
630.2 nm photospheric
Magnetogram Workshop, April 2007

15. Sample VSM Stokes Profiles
Example Stokes profile fits using EHF (Expansion in Hermite Functions)
Magnetogram Workshop, April 2007

16. Photospheric Vector Info: QL example (from 3/2/2007)
Magnetogram Workshop, April 2007

17. Summary
Finalizing the processing of Fe I nm magnetograms. This line has greater sensitivity, plus “simpler” spectra in umbral regions, than Fe I nm. The 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 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.
Magnetogram Workshop, April 2007