Solar Coronal Data

The Solar Corona is the outermost layer of the sun's atmosphere--a very hot halo (millions of degrees), that, in the form of the solar wind, extends well past the Earth's orbit. The corona is observed in detail during solar eclipses. In practice, the corona is observed routinely by ground-based and satellite coronagraphs in the red line Fe X (634.7nm -- ten times ionized iron line) and the green line Fe XIV (530.3 nm -- 14 times ionized iron line), and occasionally in the high energy yellow line Ca XV (569.4 nm -- 15 times ionized Calcium line). White light observations of the solar corona are also made routinely, and used for detecting coronal mass ejections (CMEs) that may affect the Earth. The coronagraph is a special telescope with an occulting disk to block the direct light of the sun and thus able to measure the brightness of the fainter and less dense corona. The intensities are recorded in tabular form, historically in 5-degree increments around the sun's disk. The data center holds data in analog form from 12 stations covering the period 1943 to present. Currently, 2 stations send daily coronal scans to the data center. A coronal activity index from Lomnicky Stit, Slovak Republic, 1939-present, is also available. Coronal data exhibit the 11 year solar cycle variation. Solar X-ray measurements since 1991 by the Yohkoh and GOES Solar X-ray Imager (SXI) satellites allow continuous coverage of the constantly changing hot solar corona.

1. Green Coronal Emission Line Observations 1939-present ---- Download Data

   Yearly files of the daily coronal intensity observations, with measurements taken every 5 degrees around the solar disk (counterclockwise). Values are in millionths of intensity of the solar disk (coronal units) and converted to the photometrical scale of Lomnicky Stit Station at a height of 40 minutes above the solar limb. Several stations were used in this database, with Lomnicky Peak being the primary station since 1965. Data are kindly provided by Dr. V. Rusin, Astronomical Institute, Slovak Academy of Sciences. Please note that all values were recomputed in 2006. For those who used the earlier version of the data for projects and need access to these, this older version is still available.

2. Green (FeXIV 530.3 nm) Line Coronal Index of Solar Activity Lomnicky Peak 1939-present ---- Download Data

   Measures the total energy emitted by the sun's outermost atmospheric layer (the corona) at a wavelength of 530.3 nanometers, from Lomnicky Peak, full disk emission values. Units are in 10**16 Watts/steradian. Yearly tables of daily full disk values are kindly provided by Dr. Voyto Rusin, Astronomical Institute, Slovak Academy of Sciences. Please note that all values were recomputed in 2006. For those who used the earlier version of the data for projects and need access to these, this older version is still available.

3. Digital Solar Synoptic map.tifs in H-alpha (656.3 nm) wavelength Carrington Rotations 1512-1796 (Sep 1966-Nov 1987) ---- Download Data

   DIGITAL SOLAR SYNOPTIC CHARTS descriptive text for Carrington Solar Rotations 1512-1796 (Sep 1966-Nov 1987) is by Patrick S. McIntosh. Solar H-alpha (wavelength 656.3 nm) synoptic charts contain a wealth of information, including the locations of filaments, filament channels, large sunspots, plage, coronal holes, and large-scale magnetic polarity. The digital versions of the charts do not include the full range of data available in the original charts, but they contain the key elements: the large-scale magnetic field structure (positive or negative polarity) and the locations of coronal holes (also positive or negative polarity).

   The H-alpha synoptic charts display the entire solar globe in cylindrical, heliographic coordinates based on Carrington Rotations of 27.2753 days. They show patterns of neutral lines (lines of magnetic polarity inversion) mapped from filaments and from a variety of chromospheric structures whose forms and presence are governed by magnetic fields [McIntosh, 1972a, 1979]. Superposed on these patterns are the coronal holes observed with x-ray images (1973-74) and inferred from Helium I (1083.0 nm) spectroheliograms (1975-1987). The rotation-averaged nature of the charts has limitations for their use in studies of the short-term evolution of features. However, for studying the longer-term evolution of the Sun, this convenient format has advantages; evident when segments of many charts are combined to form stackplots.

   There is one file for each digital synoptic chart covering a single Carrington Rotation of the Sun. Within each file, a pixel value is defined at each one degree of location, either in longitude (0 to 359 degrees) or in latitude (90 degrees north to 90 degrees south). This gives a total of 360x181 data points. Actual data fall into the latitude range of 75 degrees north to 75 degrees south latitude. Pixel values are coded 1 to 5, signifying coronal hole and magnetic field polarities -- see the and legend. These synoptic map pixel files are also plotted in tif format.

4. Solar Coronal Hole Data 1970-1995 -- Report UAG-102 Catalogue of Coronal Holes 1970-1991 by A. Sanchez-Ibarra and M. Barraza-Paredes, with additional data through September 1995

   Coronal Holes were first noted as M regions that produced periodic geomagnetic disturbances. These were first observed in 1970 by instruments on the Orbiting Solar Observatory (OSO) satellites, and also were noted with optical observations during the total solar eclipse of March 7, 1970. The Apollo Telescope Mount (ATM) on the Skylab manned mission observed in short wavelengths the real nature of Coronal Holes as regions of lower density and temperature than the rest of the solar corona. Three observational periods from Skylab produced substantial data on the development of Coronal Holes as well as their relationship with other types of solar activity. After Skylab, although Coronal Holes were later deduced from radio observations, the main data were obtained by observing the He I 10830A line at the Vacuum Solar Telescope at Kitt Peak National Observatory. These data, continuous from 1977 to date, were published in Solar-Geophysical Data (SGD) as Helium synoptic charts by Carrington Rotation or as Coronal Hole contours plotted on H-alpha synoptic charts. The Skylab observations of Coronal Holes were the subject of exhaustive examination. However, the main data source on Coronal Holes were the synoptic maps published in SGD. This compilation was motivated by the lack of a global reference guide. It Intends to help many statistical researchers by making it easier to work with more organized information spanning a little more than one and a half solar cycles. Although this catalogue is based only on summary data for each Carrington Rotation, it presents interesting values and enough data to analyze several aspects of the evolution of Coronal Holes.

   Coronal Holes are almost permanently visible on solar poles, except at the time of the maximum of solar cycle, when polarity inversion occurs. It is very common that coronal holes on solar poles expand to lower solar latitudes, following a sector of equal polarity. Moreover, isolated coronal holes appear at several latitudes at any time, connecting or disconnecting with holes prolongated from the pole. We classify coronal holes by two types: those which are an extension from the Coronal Holes at the poles (Polar Coronal Holes), and those which are isolated at any latitudes (Equatorial Coronal Holes). Measurements of Coronal Holes were made on the position and the extension over boundaries marked in synoptic charts. Both heliographic latitude and Carrington longitude of each hole were measured in the middle points of their north-south and east-west boundaries.

   August 1-September 30, 1995, Coronal Holes are measured on a daily basis from images taken from the Soft X-ray Telescope on board the YOHKOH Japanese spacecraft instead of the previous method of reducing the data solely from Kitt Peak Vacuum Telescope He 1083 nm images. Daily YOHKOH Soft X-ray Telescope combined images with a grid overlay are used to determine heliocentric coordinates of coronal holes. A daily synoptic chart is used to help in the identification of both equatorial (isolated) and polar (polar extension) holes. Images are calibrated using as a reference the level of brightness from holes at the poles to identify the lower densities of the corona. Preliminary identification and measurements of positions and extensions of the holes are done daily with the uncertainty level remarked. These data are on-line after 1900 UT daily at our World Wide Web Internet site (http://www.uson.mx/unison/eos/eos.htm). An extended revision is done every month before publishing the data. Identification of the coronal hole's main polarity is made using magnetograms from the National Solar Observatory Kitt Peak Vacuum Telescope -- descriptive text.

   • Catalogue of Coronal Holes 1970-1991 -- Report UAG-102 descriptive text
   • Format
   • Table 1 -- Catalog of polar holes 1970-July 1995
   • Table 2 -- Catalog of equatorial holes 1970-July 1995
   • Table 3 -- Catalog of long duration polar holes 1970-July 1995
   • Table 4 -- Catalog of long duration equatorial holes 1970-July 1995
   • Table 5 -- Catalog of all holes August-September 1995