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Solar Photosphere

The solar photosphere is sometimes referred to as the visible solar surface. It is the layer of the Sun where plasma density is low enough that most of the radiation in the optical part of the electromagnetic spectrum begins propagating freely into space. Sunspots and faculae are observed as variations in the almost uniform brightness of the photosphere.

NOAA/NCEI has acquired these legacy data sets from multiple sources over many decades. The data presented here are provided, ‘as is,’ and in most cases the linked documentation is the entirety of available information. In some cases, older data may also be found in the Space Weather Legacy Print Publications.

Questions and comments may be directed to ncei.info@noaa.gov. 

White-light image of the solar disk (1998-08-13) from the Debrecen Observatory.

White-light image of the solar disk (08-13-1998) from the Debrecen Observatory.

Synoptic charts represent two dimensional maps of the entire surface of the photosphere usually constructed from observations taken at disk center over a full solar rotation period.

Datasets

Sunspot Numbers

The relative sunspot number is an index of the activity of the entire visible disk of the Sun. It is determined each day without reference to preceding days. Each isolated cluster of sunspots is termed a sunspot group, and it may consist of one or a large number of distinct spots. The international sunspot number is produced and continually maintained by the Solar Influences Data Analysis Center (SIDC), World Data Center for the Sunspot Index, at the Royal Observatory of Belgium. The SIDC Sunspot Index and Long-term Solar Observations Site has the most up-to-date data and published sunspot numbers, and we recommend using their data for scientific analyses. The below historical data are preserved for the record. Many of these data sets have since been reprocessed, and that work is not reflected in these data.

Datasets

Sunspot Drawings

Photometry

The data presented here are based on synoptic full-disk images obtained by photoelectric photometry of sunspots at the solar San Fernando Observatory (SFO) at the 672.3 nm wavelength (see Chapman et al., 1989, 1992, 1994). Rapid changes in the total solar irradiance from space borne sensors are largely due to the passage of large sunspots across the disk. The effects of sunspots have often been modeled using ground-based observations by the use of a Photometric Sunspot Index (PSI), usually assuming all sunspots have the same thermal structure. The SFO data measures the mean temperature or bolometric contrast and corrected hemispherical areas, incorporating these into the PSI calculation.  

The tables give the date and time of the observations, the hemispherical area in pixels (5" square), the corrected total area, corrected umbral area, photometric deficit, and photometric sunspot index (PSI) in parts per million (PPM) of the solar hemisphere (millionths of the solar hemisphere). Zeros mean there were no sunspots visible. In the 1985 data there are no times for the first nine entries which were made before the clock was on-line. Also, there are some days with inconsistent UT date and time because the SFO date does not change when observations continue past 24:00:00 UT.  If an observation is shown with a UT time of between 00:00:01 and 03:00:00 UT, then that observation belongs to the previous UT day. The date is always the correct local date.

White light

Full disk white light observations from a number of observatories are linked below. Some of the files are scans of photographic plates (JPG) with handwritten markings to indicate the solar frame of reference. The 
United States Air Force (USAF) Improved Solar Observing Optical Network Limb (ISOON) data products (PDF) include some level of automated analysis to identify active region location and coverage.

Photographs

Drawings

Daily (with some gaps) full Sun drawings of solar features from various sources and observatories.

Product Details And Data

Solar Indices Bulletin is a prompt monthly information product that is distributed within two weeks after the observation month closes. For the month just ended, this 2-page circular tabulates daily values of sunspot numbers and 10.7 cm solar radio flux observed at Penticton (previously at Ottawa); flux measurements at eight other wavelengths are included.

Page 2 of the Bulletin gives a table of smoothed monthly mean sunspot numbers for the current solar cycle--a table that begins with smoothed observed values for each month and ends with predictions.

1995 - 2015, PDF

White Light

Solar White Light Faculae are areas of bright plages on the solar disk. These were routinely measured at the Royal Greenwich Observatory in the UK from 1874 to 1976, producing a record of over 100 years of continuous monitoring of this solar phenomenon. Detailed positions and areas of sunspots and faculae for each day in the year are available. As part of a data rescue effort in 1999, NOAA had these analog records keyed into digital form.

The record includes photograph time, observing station (Greenwich, Cape of Good Hope, Kodaikanal, and Mauritius), group number, position of the spot group and/or faculae, area of the spots, and faculae area for each group. The dark sunspot group areas block the solar radiation from the Sun. The bright white light faculae enhance the solar radiation from the Sun. Models of the total solar irradiance include both these opposing forces of dark sunspot group areas and the bright white light faculae areas.

Greenwich data are also available via Solar Sunspot Regions in a different format, compiled by Fred Ward, USAF AFCRL, in the 1960s and later updated by Doug Hoyt in the 1990s. The Greenwich data books have two sections and the data are somewhat different between the two sets.