National Solar Observatory/ Kitt Peak Synoptic Solar Data

The National Solar Observatories have made data available on-line.

The data are produced with the NSO Vacuum Telescope located on Kitt Peak,
Arizona. There are several types of data derived from daily full disk
observations of the sun.

**** ASCII files ****
1. A file named mag.dat contains daily averages of the magnetic field.
2. A file named he.dat contains daily values of the equivalent width
of the 1083 nm HeI line averaged across the solar disk.

**** FITS files ****
These data are images of the sun in the FITS format. Experiments with
widely available compression algorithms show only modest reduction in the
size of these files can be realized so they are unaltered.

1. Synoptic magnetogram maps, one per Carrington rotation.
2. Synoptic HeI 1083 nm maps, one per Carrington rotation.

Each of these maps represents one Carrington rotation of the sun. Longitude
increases from left to right (or increasing pixel number) in steps of
1 degree starting at 0 degrees. There are therefore 360 elements in each
row. There are 180 rows which represent equal steps in the sine of the
latitude ranging from -1 (south pole) for row 1 to +1 for row 180 (north
pole).

There are two types of maps prefixed with an m to denote line of sight
magnetic field strength in gauss and with an h to denote the strength of
the 1083 nm neutral helium line in arbitrary but constant units. The next
4 digits represent the Carrington rotation number. The suffix 'fits'
means that the maps are in a standard fits format. Specifically, each
pixel is represented as a two's complement integer value in 16 bits.
To maintain resonable precision, a bscale value of 0.1 was used meaning
that the values were divided by 0.1 before being converted to the fits
format.

The maps were constructed by making a weighted average of daily maps of
the sun. The original observations were made with 1 arc sec pixels and
then converted to daily, low resolution maps in a Carrington longitude vs.
sine latitude format. The original synoptic maps exist in a 32 bit, floating
point format in several versions at NSO/Tucson. The series starts with
rotation 1601 for magnetic measurements and 1611 for the 10830 observations.
To conserve disk space only data since 1985 are placed here in a slightly
less precise format than the original maps.

The zero level of the magnetic data has a slight positive bias since early
1985. That is, a value of about 0.3 gauss should be subtracted from all the
measurements from rotation 1762 onward.

3. Daily magnetograms.
4. Daily 1083 nm maps.

These images have been reduced from the original one arc sec per pixel
resolution to four arc sec per pixel. The pixels in each row run from
heliographic east to west. The first row is at the south and the last row
is toward the north. The naming convention is m (or) hyymmdd.fits.
Data are available from: "http://nsokp.nso.edu/dataarch.html"
Current images and data are available from "http://diglib.nso.edu/recent.html"