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SOLIS: Status and results. Alexei A. Pevtsov (National Solar Observatory, USA). SOLIS.

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solis status and results
SOLIS: Status and results

Alexei A. Pevtsov

(National Solar Observatory, USA)



Synoptic Optical Long-term Investigations of the Sun (SOLIS) is a synoptic facility for solar observations over a long time frame that is funded by the National Science Foundation (NSF) and designed and built by the National Solar Observatory (NSO).




  • SOLIS is composed of a single equatorial mount carrying three instruments:
  • the 50 cm Vector Spectromagnetograph (VSM), Fe I 6301-02, Ca II 8542, He I 10830
  • the 14 cm Full-Disk Patrol (FDP), and
  • the 8 mm Integrated Sunlight Spectrometer (ISS).
  • In operation since 2003, plans for relocation and upgrades
solis vsm

The Vector Spectromagnetograph (VSM) is designed to obtain high- quality magnetic field observations in the photosphere and the chromosphere.






Long-term spectral irradiance


Old Sac Peak CaK observations

recent improvements
Recent Improvements
  • SOLIS/VSM full Stokes profiles are now inverted using VFISV (Very Fast Inversion) code developed by J.M. Borrero et al. (2009) for the Helioseismic and Magnetic Imager (HMI) on NASA's Solar Dynamics Observatory.
  • SOLIS synoptic maps are produced via same interface as GONG maps .
  • Synoptic maps of photospheric vector magnetic field (Carrington rotations CR2109-2131).



nisp atmosphere highlights
NISP/Atmosphere Highlights
  • Effect of uncertainties in synoptic maps on potential field extrapolation
  • Sun-as-a-star research (CaK basal profiles)
  • Vector field synoptic maps and helicity studies
  • Large-scale NLFFF modeling
  • Current/magnetic and kinetic helicity
cak basal profiles solis iss
CaK Basal Profiles (SOLIS/ISS)
  • Basal profiles represent non-magnetic chromosphere and thought to be independent of solar cycle
  • SOLIS/ISS data from Dec 2006 – July 2011
  • Deconvolved quiet-Sun and active-Sun profiles and studied their cycle variation

Pevtsov et al, 2013

cak basal profiles
CaK Basal Profiles
  • Basal profiles originating from the non-magnetic chromosphere may vary slightly between the minimum and rising phase of the sunspot cycle.
  • This may indicate a possible change in properties of “mean” chromosphere with phase of the solar cycle.
  • For active-Sun profiles, we see a difference in amplitude between K2R and K2V, which may be related to dependency of flux of acoustic waves on the phase of solar cycle.

Reference range “a”

Reference range “b”

Reference range “c”

K3 of basal profile

K3 in basal profile vary with solar cycle;

three reference ranges (a-c) do not.

synoptic vector maps solis vsm
Synoptic Vector Maps (SOLIS/VSM)


  • Weak photospheric fields systematically deviate from vertical direction
  • Hemispheric helicity rule is confirmed.
  • Helicity has opposite sign for strong and weak fields



Gosain et al (2013)

synoptic vector maps in nlfff global modeling solis vsm
Synoptic Vector Maps in NLFFF Global Modeling (SOLIS/VSM)

NLFFF global model

EIT image

Magnetic free energy


  • First ever use of synoptic vector maps for NLFFF extrapolation
  • Magnetic free energy can be used to characterize flare/CME potential of active regions.

80 Mm above photosphere

Tadesse et al (2013)

helicity of subsurface flows and photospheric magnetic fields
Helicity of subsurface flows and photospheric magnetic fields
  • Current helicity of photospheric field and kinetic helicity of subphotospheric flows have the same sign
  • In about 70% of all locations, kinetic helicity follows the hemispheric rule
  • Amplitude of kinetic helicity is larger in areas of sunspot activity
  • There is an indication of possible reversal in helicity rule for kinetic helicty early in Cycle 24 in low latitudes.

Current helicity (SOLIS/VSM)

Kinetic helicity (GONG)

Komm et al, 2013