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The Wilcox Solar Observatory

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The Wilcox Solar Observatory (WSO) began collecting daily observations of the Sun's global (or mean) magnetic field in May 1975 (Scherrer+1977), with the goal of understanding changes in the Sun and how those changes affect the Earth. That science is called space weather. Since May 1976 daily low-resolution maps of the Sun's magnetic field have been made at WSO, along with observations of solar surface motions. The observatory is located in the foothills just south of the Stanford University main campus.

Current WSO research topics include space weather, the large-scale magnetic field, and the solar cycle. The observatory and staff are also associated with the Helioseismic and Magnetic Imager (HMI) project on the Solar Dynamics Observatory (SDO) and the COFFIES DRIVE Science Center. HMI provides continuous real-time high-resolution solar observations of the velocity, intensity, and magnetic field from geosynchronous Earth orbit. The Solar Observatories Group previously operated the Solar Oscillations Investigation that uses the Michelson Doppler Imager (MDI) instrument on the SOHO spacecraft to observe the inside of the Sun.

More information is available concerning the Solar Observatories Group, the Hansen Experimental Physics Laboratory (HEPL), the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), and about the Experimental and Observational Astrophysics and Cosmology and Theoretical Astrophysics and Cosmology programs in the Stanford University Physics Department.

NASA funding for WSO ended in 2018. Historically WSO has been supported by NASA Heliophysics, the NSF, and the Office of Naval Research.
Prof. J. Todd Hoeksema serves as WSO director.

	Visit the SOLAR Center -- our award winning educational web site providing on-line activities to encourage and share the wonder of solar science exploration. You can also learn about Space Science at Windows to the Universe. When is Sunrise?	The Sky Above

** ** ** Announcements ** ** **

The WSO Guiding System stopped magnetogram observations again on January 11, 2026. We are still working to fix it (March 2026).
The Guiding System was restored and magnetograms resumed on June 15, 2025.
A problem with the WSO Guiding System stopped magnetogram observations on April 10, 2025.

WSO Solar Magnetic Field Observations

• Latest Preliminary Magnetogram: [.gif] | [.ps], Synoptic Chart [.gif] | [.ps], or Coronal PFSS map [.gif] | [.ps].
• Form for requesting WSO Synoptic Data.
• Summary and Complete descriptions of available WSO data. (Note - formulae refer to Classic PFSS model coefficients.)
• How to use Harmonic Coefficients (Radial PFSS Model Coefficients) in the PFSS model.
• The WSO Data Use Policy and References.

Magnetograms

sn=16752 time=2026:01:10_20h:07m:53s CT2306:170 trouble=40000001 sky= 5 NOTE: 1 not complete 24 do not use for anything!
	Most recent WSO Magnetogram
	[.gif] | [.ps]

Daily Magnetogram Atlases

• Contour: GIF, PS, & PDF: DAILY magnetograms plots available from 1994 onward showing B as well as Velocity and Intensity (updated monthly)
• Contour Postscript and gif Daily photospheric magnetic field: 1995-present (updated daily). This year:
  2025: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec
  2024: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec
  2023: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec
  2022: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec
  2021: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec
  2020: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec
  2019: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec
• Colorized GIF: An atlas of magnetograms in gif format since 1988.

Synoptic Charts of the Photospheric Magnetic Field

• An ATLAS [GIFs, PS plots + Tables] of photospheric field synoptic charts for Carrington Rotations since May 1976 or
• A preliminary plot of the most recent 360 degrees: [gif] [ps] of data. [pdf] of data.

Computed Coronal Field Maps

• An ATLAS [GIFs & PS plots + Tables] of computed coronal field synoptic charts since May 1976 or
• Our most recent preliminary classic 360 degrees [ps] line-of-sight computation.
• Our most recent preliminary radial Rs=2.5: 360 degrees [ps] computations.
• Our most recent preliminary radial 3.25 Rs: 360 degree [ps] calculations.

Numerical Data Tables

• Synoptic Charts and
• Harmonic Coefficients and
• Level 3 Magnetograms

Radial Boundary Condition
• Latest Harmonic Coefficients to order 20; an archive of daily coefficients.
• Radial Harmonic Coefficient for each rotation.
• See .txt entries in the WSO model coronal field ATLAS
Classic Line-of-Sight Photospheric Boundary Condition Rs=2.50 with standard polar field correction
• Harmonic Coefficients
• See .txt entries in the WSO model coronal field ATLAS
• Latest preliminary values.

The Mean Magnetic Field of the Sun

Warning: WSO Polarization Sensitivity was reduced from 16 December 2016 to 18 May 2017.
Mean field values have NOT been recalibrated and are a factor of about 1.55 too small during that interval.

2020 |	2021 |	2022 |	2023 |	2024 |	2025 |
2010 |	2011 |	2012 |	2013 |	2014 |	2015 |	2016 |	2017 |	2018 |	2019 |
2000 |	2001 |	2002 |	2003 |	2004 |	2005 |	2006 |	2007 |	2008 |	2009 |
1990 |	1991 |	1992 |	1993 |	1994 |	1995 |	1996 |	1997 |	1998 |	1999 |
1980 |	1981 |	1982 |	1983 |	1984 |	1985 |	1986 |	1987 |	1988 |	1989 |
					1975 |	1976 |	1977 |	1978 |	1979 |

• Complete MF Time Series from 1975:05:16 to 2024:03:19
• 45-year MF Plot showing data from May 1975 - March 2024: postscript gif
• Recent meanfield plot in Bartels calendar: .ps | .gif .

Other Quantities