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Sac Peak Full-Disk Coronal Map GIF Images...(1Sep93)
Available through Anonymous FTP
(from NSO, NOAO Newsletter No. 35, 1 September 1993)

The Solar Terrestrial Dispatch in cooperation with the USAF Phillips
Laboratory and the National Solar Observatory are pleased to announce
the availability of pseudo-full-disk solar Fe XIV 5303 A and Ca XV 5694 A
coronal map images through anonymous FTP from: XI.ULETH.CA (IP number
142.66.3.29).

Maps are provided on a daily basis at this site in the directory
"pub/solar/Corona/Maps" as GIF-image files.

Observations are made at the National Solar Observatory at Sacramento
Peak with the Emission Line Coronal Photometer (ELCP). This instrument
photoelectrically records the solar corona when fed with the Evans
Solar Facility 40-cm Coronagraph. It operates at high precision due to
its ability to subtract the sky background from the signal in emission
lines through use of a lock-in amplifier oscillating at a rate of 100
kHz between the continuum and lines at 6374 A (Fe X), 5303 A (Fe XIV) and
5694 A (Ca XV), which are formed at approximate temperatures of 1, 2 and
3 MK, respectively. A 1.1 arcmin aperture is scanned around the limb
daily from 1.15 to 1.45 solar radii for Fe XIV, 1.13 Ro for Ca XV and
1.15 Ro for Fe X. The output of the ELCP is sensed by a
photomultiplier, digitized and recorded every 3 degrees of latitude.
Absolute intensities in millionths of the brightness of the center of
the disk at each wavelength are obtained by calibrating the system
through a neutral density filter. All Fe X, Ca XV and the 1.45 Ro Fe
XIV scans are scaled to have at least one absolute zero intensity data
point. Fe XIV scans at other radii are adjusted by the amount
subtracted from the 1.45 Ro scan.

Pseudo-full-disk maps are produced by joining together 15 days of 1.15
Ro (Fe XIV) or 1.13 Ro (Ca XV) data from the East or West limbs into a
synoptic map and projecting it onto a sphere. For the East-limb maps,
the scan from the date of the map is at the left side (East) of the
map, and the data on the central meridian are from seven days prior to
the date of the map. West-limb maps, which show the far-side of the Sun
on the day they are produced, have been given an effective date two
weeks into the future, so that they may be compared with East-limb maps
of the same date. Under this naming convention, both East- and
West-limb maps show the Earth-facing side of the Sun. For the West-limb
maps, the scan from 14 days before the date of the map is at the left
side (East) of the map, and the data on the central meridian are from
21 days prior to the date of the map. Data are incremented from the
central meridian at 12.857 degrees per day. For Fe XIV maps, all
missing data are interpolated. For Ca XV maps, single missing days are
interpolated; two or more consecutive missing days are shown as "N/A"
(not available < =>  black). Maps are currently only produced for Fe XIV
and Ca XV and are normally available for each Monday through Friday,
excluding holidays.

Each image in the "pub/solar/Corona/Maps" directory contains both an Fe
XIV and a Ca XV map. The images are identified as "mapMMDDx.gif", where
MM is the month, DD is the date, and "x" is "e" or "w". East-limb data
are identified in the filenames by postfixing the date with an "e"
(e.g., "map0512e.gif" for 12 May). West-limb data are similarly
identified with a "w" postfixed to the date (e.g., "map0526w.gif" for
26 May).

These data are freely available with one restriction:  If you use the
data or some product based on the data in a published paper, we ask
that you include an acknowledgement as follows:

NSO data used here are produced cooperatively by USAF/AFMC/PL/GPSS and
NSF/NOAO/NSO/SP.

GIF image plots are produced cooperatively by the above and the Solar
Terrestrial Dispatch.

For further information, contact thenry or raltrock at NOAO:: or
noao.edu.

CAUTION: Contact the above for current information concerning
calibration before using these maps for any modeling, etc.,
applications requiring absolute calibrations.

For questions or problems concerning this service, contact:
Oler@Rho.Uleth.CA, Solar::COler or COler@Solar.Stanford.Edu

Dick Altrock

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