Solar Physics

, Volume 282, Issue 1, pp 91–106 | Cite as

Comparison of Ground-Based and Space-Based Longitudinal Magnetograms

  • A. PietarilaEmail author
  • L. Bertello
  • J. W. Harvey
  • A. A. Pevtsov


We compare photospheric line-of-sight magnetograms from the Synoptic Optical Long-term Investigations of the Sun (SOLIS) Vector Spectro-Magnetograph (VSM) instrument with observations from the 150-foot Solar Tower at Mt. Wilson Observatory (MWO), the Helioseismic and Magnetic Imager (HMI) on the Solar Dynamics Observatory (SDO), and the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO). We find very good agreement between VSM and the other data sources for both disk-averaged flux densities and pixel-by-pixel measurements. We show that the VSM mean flux density time series is of consistently high signal-to-noise ratio with no significant zero offsets. We discuss in detail some of the factors – spatial resolution, flux dependence, and position on the solar disk – affecting the determination of scaling between VSM and SOHO/MDI or SDO/HMI magnetograms. The VSM flux densities agree well with spatially smoothed data from MDI and HMI, although the scaling factors show a clear dependence on flux density. The factor to convert VSM to HMI increases with increasing flux density (from ≈1 to ≈1.5). The nonlinearity is smaller for the VSM vs. SOHO/MDI scaling factor (from ≈1 to ≈1.2).


Magnetograms Photosphere Solar magnetic fields 



We thank R.K. Ulrich for providing the MWO mean flux time series. The SOLIS data used here are produced cooperatively by NSF/NSO and NASA/LWS. HMI/SDO is a project of NASA. MDI/SOHO is a project of international cooperation between ESA and NASA.


  1. Balasubramaniam, K.S., Pevtsov, A.: 2011, Ground-based synoptic instrumentation for solar observations. In: Fineschi, S., Fennelly, J. (eds.) Solar Physics and Space Weather Instrumentation IV., Proc. SPIE 8148, 814809. Google Scholar
  2. Berger, T.E., Lites, B.W.: 2002, Weak-field magnetogram calibration using Advanced Stokes Polarimeter flux-density maps – I. Solar Optical Universal Polarimeter calibration. Solar Phys. 208, 181. ADSCrossRefGoogle Scholar
  3. Berger, T.E., Lites, B.W.: 2003, Weak-field magnetogram calibration using Advanced Stokes Polarimeter flux density maps – II. SOHO/MDI full-disk mode calibration. Solar Phys. 213, 213. ADSCrossRefGoogle Scholar
  4. Cauzzi, G., Smaldone, L.A., Balasubramaniam, K.S., Keil, S.L.: 1993, On the calibration of line-of-sight magnetograms. Solar Phys. 146, 207. ADSCrossRefGoogle Scholar
  5. Demidov, M.L., Golubeva, E.M., Balthasar, H., Staude, J., Grigoryev, V.M.: 2008, Comparison of solar magnetic fields measured at different observatories: peculiar strength ratio distributions across the disk. Solar Phys. 250, 279. ADSCrossRefGoogle Scholar
  6. Freeland, S.L., Handy, B.N.: 1998, Data analysis with the SolarSoft System. Solar Phys. 182, 497. ADSCrossRefGoogle Scholar
  7. Harvey, J.W., Branston, D., Henney, C.J., Keller, C.U., SOLIS and GONG Teams: 2007, Seething horizontal magnetic fields in the quiet solar photosphere. Astrophys. J. Lett. 659, L177. ADSCrossRefGoogle Scholar
  8. Isobe, T., Feigelson, E.D., Akritas, M.G., Babu, G.J.: 1990, Linear regression in astronomy. Astrophys. J. 364, 104. ADSCrossRefGoogle Scholar
  9. Jones, H.P.: 1996, Online analysis and compression of spectra-spectroheliograms. In: Rust, D.M. (ed.). Missions to the Sun, Proc. SPIE 2804, 110. Google Scholar
  10. Jones, H.P., Ceja, J.A.: 2001, Preliminary comparison of magnetograms from KPVT/SPM, SOHO/MDI and GONG+. In: Sigwarth, M. (ed.) Advanced Solar Polarimetry – Theory, Observation, and Instrumentation, ASP Conf. Ser. 236, 87. Google Scholar
  11. Jones, H.P., Duvall, T.L. Jr., Harvey, J.W., Mahaffey, C.T., Schwitters, J.D., Simmons, J.E.: 1992, The NASA/NSO spectromagnetograph. Solar Phys. 139, 211. ADSCrossRefGoogle Scholar
  12. Jones, H.P., Harvey, J.W., Henney, C.J., Keller, C.U., Malanushenko, O.M.: 2004, Measurement scale of the SOLIS vector spectromagnetograph. Bull. Am. Astron. Soc. 36, 709. ADSGoogle Scholar
  13. Keller, C.U., Harvey, J.W., Giampapa, M.S.: 2003, SOLIS: An innovative suite of synoptic instruments. In: Keil, S.L., Avakyan, S.V. (eds.) Innovative Telescopes and Instrumentation for Solar Astrophysics, Proc. SPIE 4853, 194. Google Scholar
  14. Leka, K.D., Barnes, G.: 2012, Modeling and interpreting the effects of spatial resolution on solar magnetic field maps. Solar Phys. 277, 89. ADSCrossRefGoogle Scholar
  15. Liu, Y., Hoeksema, J.T., Scherrer, P.H., Schou, J., Couvidat, S., Bush, R.I., Duvall, T.L., Hayashi, K., Sun, X., Zhao, X.: 2012, Comparison of line-of-sight magnetograms taken by the Solar Dynamics Observatory/Helioseismic and Magnetic Imager and Solar and Heliospheric Observatory/Michelson Doppler Imager. Solar Phys. 279, 295. ADSCrossRefGoogle Scholar
  16. Livingston, W.C., Harvey, J., Pierce, A.K., Schrage, D. Gillespie, B., Simmons, J., Slaughter, C.: 1976a, Kitt Peak 60-cm vacuum telescope. Appl. Opt. 15, 33. ADSCrossRefGoogle Scholar
  17. Livingston, W.C., Harvey, J., Slaughter, C., Trumbo, D.: 1976b, Solar magnetograph employing integrated diode arrays. Appl. Opt. 15, 40. ADSCrossRefGoogle Scholar
  18. Rees, D.E., Semel, M.D.: 1979, Line formation in an unresolved magnetic element – A test of the centre of gravity method. Astron. Astrophys. 74, 1. ADSGoogle Scholar
  19. Scherrer, P.H., Bogart, R.S., Bush, R.I., Hoeksema, J.T., Kosovichev, A.G., Schou, J., et al.: 1995, The Solar Oscillation Investigation – Michelson Doppler Imager. Solar Phys. 162, 129. ADSCrossRefGoogle Scholar
  20. Scherrer, P.H., Schou, J., Bush, R.I., Kosovichev, A.G., Bogart, R.S., Hoeksema, J.T., et al.: 2012, The Helioseismic and Magnetic Imager (HMI) investigation for the Solar Dynamics Observatory (SDO). Solar Phys. 275, 207. ADSCrossRefGoogle Scholar
  21. Thornton, C.E., Jones, H.P.: 2002, Comparison of three solar magnetographs. Bull. Am. Astron. Soc. 34, 1243. ADSGoogle Scholar
  22. Tran, T., Bertello, L., Ulrich, R.K., Evans, S.: 2005, Magnetic fields from SOHO MDI converted to the Mount Wilson 150 foot Solar Tower scale. Astrophys. J. Suppl. 156, 295. ADSCrossRefGoogle Scholar
  23. Ulrich, R.K., Evans, S., Boyden, J.E., Webster, L.: 2002, Mount Wilson synoptic magnetic fields: Improved instrumentation, calibration, and analysis applied to the 2000 July 14 flare and to the evolution of the dipole field. Astrophys. J. Suppl. 139, 259. ADSCrossRefGoogle Scholar
  24. Wenzler, T., Solanki, S.K., Krivova, N.A., Fluri, D.M.: 2004, Comparison between KPVT/SPM and SoHO/MDI magnetograms with an application to solar irradiance reconstructions. Astron. Astrophys. 427, 1031. ADSCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2012

Authors and Affiliations

  • A. Pietarila
    • 1
    Email author
  • L. Bertello
    • 1
  • J. W. Harvey
    • 1
  • A. A. Pevtsov
    • 2
  1. 1.National Solar ObservatoryTucsonUSA
  2. 2.3010 Coronal LoopNational Solar ObservatorySunspotUSA

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