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SYNOPTIC MAPS OF SOLAR CORONAL HOLE BOUNDARIES
DERIVED FROM He II 304 A SPECTROHELIOGRAMS
FROM THE MANNED SKYLAB MISSIONS:

24 May - 23 June 1973
2 August - 24 September 1973
21 November 1973 - 2 February 1974

by

J. D. Bohlin and D. M. Rubenstein
E. 0. Hulburt Center for Space Research
Naval Research Laboratory
Washington, D. C. 20375 U.S.A.

ABSTRACT

The disk boundaries of coronal holes have been determined from He II 304 A
spectroheliograms which were taken with the Naval Research Laboratory (NRL)
slitless XUV spectrograph during the manned Skylab missions. These boundaries
are plotted by Carrington rotation as synoptic charts in both the standard
rectangular as well as polar-view projections. The polar-view projections
emphasize that the major areas occupied by coronal holes during this period
were in the polar caps at latitudes 260° North and South. The periods of
time for which boundaries were determined are 24 May through 23 June 1973
(first manned Skylab mission), 2 August through 24 September 1973 (second
manned mission), and 21 November 1973 through 2 February 1974 (third
manned mission); the Carrington rotations covered (in part or totally)
are 1601 and 02; 1604, 05 and 06; and 1608, 09 and 10, respectively.

These charts are presented for use in the study of Skylab and corrobo-
rating space/ground-based data taken during the manned mission periods.

One of the earliest and most surprising discoveries from the NRL Skylab data was that the
resonance line of singly ionized helium, He II 304 A, reveals the presence of a coronal hole as a
region of decreased emission and loss of definition of the chromospheric network [Tousey et al.,
1973; Brueckner and Bartoe, 1974; Bohlin et al., 1975 a,b,c]. It is not obvious why this emission
line of helium, which theoretically forms in the upper chromosphere at 6-10 x 10"K, should reflect
large-scale temperature and density depressions in the overlying corona, especially since other XUV
chromospheric lines show a much less pronounced effect [Brueckner and Bartoe, 1974; Huber e¢ aZ.,
1974], Several theories have been advanced to account for this apparent anomaly, but it is outside
the scope of this atlas to discuss them here. For our purposes it is sufficient only to note that
usually a distinct and unambiguous He II 304 A signature of the coronal holes does exist and can be
used to determine their boundaries, subject to the limitations discussed below.

These data are presented here without interpretation or comparison to other observations. How-
ever, several papers have discussed the XUV phenomena of coronal holes (see references above), and
these particular maps have been used to derive a number of general conclusions concerning the evo-
lution of coronal holes and their relationship to large-scale magnetic fields [Bohlin et al., 1975c];
a more detailed paper is currently in preparation.

These He II coronal hole maps were generated from a standard series of exposures made daily
(typically 1200 to 1600 UT) throughout the manned Skylab missions under the general heading of the
synoptic program [Reeves et al., 1972]. High-contrast transparency enlargements were used to deter-
mine, by visual inspection, the coronal hole boundaries. Their heliocentric coordinates were
digitized directly using overlay projections of spherical coordinates (i.e., Stonyhurst disk grids)
and then plotted by computer in rectangular and polar projections. The elements of this Program are
considered in detail in the following paragraphs:

i) Validity of He IIT 304 A as an Indicator of Coronal Holes

The question is not whether He II 304 A spectroheliograms exhibit regions of abnormally low
intensity and lack of chromospheric network, but whether these regions reliably outline coronal holes.
With only a few exceptions, it has been found [Bohlin e¢ aZ., 1975c] that this resonance line of
helium does reveal the large-scale coronal hole boundaries to a high degree of accuracy when compared
to the soft X-ray coronal images obtained by the American Science and Engineering (AS&E) experiment

1



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UAG-35

UAG-36

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UAG-38

UAG-39

UAG-40

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UAG-45,

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"Catalogue of Digital Geomagnetic Variation Data at World Data Center A for Solar-Terrestrial
Physics", prepared by Environmental Data Service, NOAA, Boulder, Colorado, July 1974, 20 pages,
price 20 cents.

"An Atlas of Extreme Ultraviolet Flashes of Solar Flares Observed Via Sudden Frequency Devia-
tions During the ATM-SKYLAB Missions", by R. F. Donnelly and E. L. Berger, NOAA Space Environ-
ment Laboratory, Lt. J. D. Busman, NOAA Commissioned Corps, B. Henson, NASA Marshall Space
Flight Center, T, B. Jones, University of Leicester, UK, G. M. Lerfald, NOAA Wave Propagation
Laboratory, K. Najita, University of Hawaii, W. M. Retallack, NOAA Space Environment Laboratory,
and W. J. Wagner, Sacramento Peak Observatory, October 1974, 95 pages, price 55 cents.

“Auroral Electrojet Magnetic Activity Indices AE(10) for 1966", by Joe Haskell Allen, Carl C.
Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Environ-
mental Data Service, December 1974, 142 pages, price 75 cents.

"Master Station List for Solar-Terrestrial Physics Data at NDC-A for Solar-Terrestrial Physics",
by R. W. Buhmann, World Data Center A for Solar-Terrestrial Physics, Juan D. Roederer, Univer-
sity of Denver, Denver, Colorado, M. A. Shea and D. F. Smart, A.F.C.R.L., Hanscom AFB, Massa-
chusetts, December 1974, 110 pages, price $1.60.

“Auroral Electrojet Magnetic Activity Indices AE(11) for 1971", by Joe Haskell Allen, Carl C.
Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Environ-
mental Data Service, February 1975, 144 pages, price $2.05.

"H-Alpha Synoptic Charts of Solar Activity For the Period of Skylab Observations, May, 1973-
March, 1974", by Patrick S. McIntosh, NOAA Environmental Research Laboratory, February 1975,
32 pages, price 56 cents.

“H-Alpha Synoptic Charts of Solar Activity Durina the First Year of Solar Cycle 20 October,
1964 ~ August, 1965", by Patrick S. McIntosh, NOAA Environmental Research Laboratory, and
Jerome T. Nolte, American Science and Engineering, Cambridge, Massachusetts, March 1075,
25 pages, price 48 cents.

"Observations of Jupiter's Sporadic Radio Emission in the Range 7.6-80 MHz 10 December 1971
through 21 March 1975", by James W. Warwick, Georae A. Dulk, and Anthony C. Riddle, Depart-
ment of Astro-Geophysics, University of Colorado, Boulder, Colorado 80302, Apri7 1975,

49 pages, price $1.15. :

“Catalog of Observation Times of Ground-Based Skylab-Coordinated Solar Observing Programs",
compiled by Helen E. Coffey, World Data Center A for Solar-Terrestrial Physics, May 1975,
159 pages, price $3.00.

"Synoptic Maps of Solar 9.1 cm Microwave Emission from June 1962 to August 1973", by Werner
Graf and Ronald N. Bracewell, Radio Astronomy Institute, Stanford University, Stanford,
California 94305, May 1975, 183 pages, price $2.55.

“Auroral Electrojet Magnetic Activity Indices AE(11) for 1972", by Joe Haskell Allen, Carl C.
Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Environ-
mental Data Service, May 1975, 144 pages, price $2.10.

"Interplanetary Magnetic Field Data 1963-1974", by Joseph H. King, National Space Science
Data Center, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, June 1975, 382
pages, price $2.95.

“Auroral Electrojet Magnetic Activity Indices AE(11) for 1973", by Joe Haskell Allen, Carl C.
Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center, Environ-
mental Data Service, June 1975, 144 pages, price $2.10.

"Synoptic Observations of the Solar Corona during Carrington Rotations 1580-1596 (11 October
1971 ~ 15 January 1973)", by R. A. Howard, M. J. Koomen, D. J. Michels, R. Tousey, C. R.
Detwiler, D. E. Roberts, R. T. Seal and J. D. Whitney, E.0. Hulbert Center for Space Research,
NRL, Washington, D. C. 20375 and R. T. and S. F. Hansen, C. J. Garcia and E. Yasukawa, High
Altitude Observatory, NCAR, Boulder, Colorado 80303, duly 1975, 200 pages, price $3.00.

"Catalog of Standard Geomagnetic Variation Data", prepared by Environmental Data Service, NOAA,
Boulder, Colorado, August 1975, 125 pages, price $1.85.

“High-Latitude Supplement to the URSI Handbook on Ionogram Interpretation and Reduction", by
W. R. Piggott, British Antarctic Survey, c/o SRC, Appleton Laboratory, Ditton Park, Slough,
England, October 1975, 292 pages, price $4.00.

“Synoptic Maps. of Solar Coronal Hole Boundaries Derived from He II 304A Spectroheliograms from
the Manned Skylab Missions", by J. D. Bohlin and D. M. Rubenstein, E. 0. Hulbert Center for
Space Research, Naval Research Laboratory, Washington, D. C. 20375 U.S.A., November 1975.

30 pages, price 54 cents.
“Experimental Comprehensive Solar Flare Indices for Certain Flares, 1970-1974", compiled by

Helen W. Dodson and E. Ruth Hedeman, McMath-Hulbert Observatory, The University of Michigan,
R95 Lake Angelus Road North, Pontiac, Michigan 48055 U.S.A., November 1975.

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d) The fine-tip pen used for tracing made a line typically 1/2° wide; and
e) The visual reading of the boundary was no more accurate than a degree and rounded to whole degrees.

Thus, for the central disk portions, assuming a random addition of errors, each boundary point has a
possible rms error of the order of 2° peak-to-peak. As a general rule this level of uncertainty is
completely dominated by the uncertainty of the boundary itself (see paragraph (iii) above) combined
with the inherent small-scale evolutionary changes in the boundaries over the three-day intervals
between observations; this latter effect alone has typical peak-to-peak values of 4 to 8°.

v) Plotting of the Data

The data have been plotted by computer to allow the option of easily displaying the same material

in different ways. In particular we have plotted the data in three formats, all by Carrington rotation:

a) Rectangular disk projections (490° latitude in width and 360° longitude in length, plus 30° overlap
at each end) with both Tatitude and longitude in equal linear scales; b) Polar-view projections
(radius = cosine of heliographic latitude) for both north and south poles; and c) Equal-area rectangu-
Jar projections (similar to (a) except the vertical scale follows the sine of the latitude). Plots

a) and (b) are contained in this atlas; plots (c) were generated for in-house study of the areas
covered by coronal holes; copies can be made available upon request. In all cases a Carrington ro-
tation rate of 13.2° per day was used. To avoid cumulative errors, each rotation was independently
registered to start with the day (to two decimal places) as listed in the Amertcan Ephemeris and
Nautical Almanac. The date scales on both the rectangular and polar plots are referenced to central
meridian passage in the usual way, and are supplemented with a day-of-year (DOY) index just inside

the boundary of the rectangular disk projection plots. The rectangular plots have been scaled to
duplicate in size the Ha synoptic charts contained in an earlier UAG Report [McIntosh, 1975].

These coronal hole charts differ from usual synoptic maps of solar activity and magnetic fields
in the fundamental respect that the data are taken from the entire disk (to typically 0.1 Rs of the
limb) on three-day centers instead of from a restricted longitude zone near central meridian every
day. The chosen three-day cadence combined with the ability to determine the boundaries to within
25° of the limb (somewhat less for the polar holes) means that any one coronal hole feature is plotted
as many as four times during a given disk passage.

The resulting multiplicity of overlapping lines may appear confusing, but retention of all the
data on these charts does have several significant advantages. First, since the coronal hole bound-
aries in certain areas occasionally could not be determined, observations three days on either side
fill in the gap. Thus the continuity of the averaged boundary is preserved. Second, since the data
were plotted independently for each day by computer, the degree to which they overlap confirms that
our original subjective determination was reasonably self-consistent and valid. Well-defined and
temporally stable boundaries frequently superpose to within a few degrees (e.g., the south polar
coronal hole in rotations 1604 and 1605). Third, failure of the boundaries to overlap is an indica-
tion that either small-scale evolution has occurred over the time scale of 3 to 12 days, or that the
boundaries themselves were initially poorly defined. In order to differentiate between the two
cases, -the original transparencies were re-examined, and cross-hatching added within the peak-to-peak
envelope of boundaries in those areas where the identification of the coronal holes was uncertain
(e.g., the north polar hole in rotation 1601 shown on the rectangular plot).

Of course, this evaluation itself is highly subjective and should be used only as an indication
that the exact boundary from He II for a given area and day could not be determined better than 3-5°
heliocentric. As a rule of thumb, a mean boundary drawn through the average of such shaded zones
will give an accurate (+ 2-4°) measure of the coronal hole.

One last point should be noted: the anomalous break in the boundaries from 4 to 7 June (rota-
tion 1602) was caused by a camera malfunction in the first manned Skylab mission, and no He II
images were exposed from 31 May through 8 June 1973.

Acknowledgements

These data were obtained under the direction of the NRL/Skylab Principal Investigator, Dr. R.
Tousey, through the dedication and untiring contributions of many individuals. In particular, the
mission science support team consisted of J. -D. F. Bartoe, G. E. Brueckner, C. C. Cheng, W. R.
Crockett, M. W. Frank, 0. K. Moe, K. R. Nicolas, N. P. Patterson, J. D. Purcell, D. Schneible,

V. E. Scherrer, W. R. Sidle, N. R. Sheeley, Jr., M. E, VanHoosier and K. G. Widing. Most of all
we acknowledge the Skylab Astronauts whose dedication and talent made Skylab such a success. This
work was supported by NASA contract DPR-S-60404-G,



on board Skylab [Timothy et al., 1975; A. S. Krieger, private communication]. The major difference
occurs in coronal holes which are undergoing rapid evolution on a time scale of a few days, as opposed
to the more usual scale of weeks. In these instances the overlying corona and He II chromospheric
patterns can be 'out of phase'; i.e., the X-ray corona can show a small hole or a fine-scale detail
in a larger coronal hole while the heliogram does not, or vice-versa. The other major difference
concerns the presence of holes in close proximity to complex active regions. Pictures which show
the corona projected on the disk, e.g., AS&E X-ray data or NRL spectroheliograms in the coronal line
Fe XV 284 R [Sheeley et aZ., 1975], often show small-scale regions of open field lines and reduced
coronal intensity in complexes of disk activity that are difficult to reliably recognize and measure
from He II 304 A images. Therefore these small active region coronal holes are not included in this
atlas.

ii) Frequency of Observation

Although daily observations were available, we soon discovered that the usually slow evolution
of the coronal hole boundaries permitted their complete documentation using frames taken at three
day intervals. This three-day cadence greatly reduced the amount of data to be digitized, at
a negligible loss in information for all but a few cases where rapid evolution was taking place.
(Those particular situations are being studied with finer time resolution for separate publ ication.)
The boundaries were determined from limb-to-limb (+ 60-70° about central meridian), so that any one
feature was determined at least three times during its disk passage.

iii) Visual Determination of Coronal Hole Boundaries from He II 304 A

After some experimentation it was found that first-generation, high-contrast transparencies
(Kodak Super Neg) seemed to be optimum for visual measurements. These enlargements (18 cm solar
diameter; “11 arc sec/mm) were examined on a light table and the boundaries of all coronal holes
were traced onto clear acetate overlay sheets using a fine-tip felt pen. The boundary lines were
determined independently for each image, without any effort to project the boundaries from a pre-
vious image forward with time. However, images three days on either side of the one being traced
were examined as an aid in those cases where evolution had changed the visibility of a hole. Cor-
responding Ho observations (provided by NOAA during Skylab) were used to discriminate long narrow
coronal holes from filaments and/or filament channels, which can be remarkably similar to coronal
holes in He II 304 A.

In spite of these aids, however, determination of coronal holes by this visual method was
fundamentally a problem of subjective pattern recognition, and thus liable to personal bias. We
guarded against bias by two techniques: First, the original sketching of the boundaries was done
by one of us alone. Then working as a team, we re-evaluated each image and its overlay tracing to
arrive at a mutually agreed-upon decision. This process was greatly facilitated by flipping the
clear overlay tracing against the spectroheliogram, a process we found to permit discrimination of
many otherwise doubtful or subtle cases. Second, to insure that our level of visual sensitivity
to the boundaries did not change over the five weeks involved in processing all the images, we re-
examined every image a second time, thereby picking up several small coronal holes and/or complexi-
ties in boundaries overlooked the first time.

However, some portions of a few boundaries remained simply too ambiguous or obscure to determine
with a reasonable level of certainty. In these cases (perhaps 25 in all) the boundaries were not
drawn. However, in every one of these instances, the boundary was sufficiently defined sometime
during its disk passage so that no break occurs when the multiple patterns are finally plotted.

iv) Transformation to Heliocentric Coordinates and Digitization of Data

These data did not warrant mathematical transformation from projected orthogonal (x, y) into
spherical heliographic coordinates, so Stonyhurst disk grids were used instead. The heliographic
latitude and longitude were read point-by-point at sufficiently fine intervals (minimum of 1°) to
specify completely the convolutions of the boundaries. In no case was the maximum interval between
two points allowed to exceed 5° in either latitude or longitude. The 38 separate spectroheliograms
required 3550 points in all to specify the boundaries.

The various uncertainties (peak-to-peak, heliocentric) for any one point in the central portion
of the disk (i.e., r < 3/4 Rg) can be estimated as follows:

a) The inherent uncertainty in determining a reasonably distinct boundary was typically ~1°;

b) A slight eccentricity in the He II solar images caused a mismatch to the circular Stonyhurst
grids of v1°;

c) The Stonyhurst grids discriminated between values of the tilt of the solar axis, B, by 1°
increments, so a maximum error of v1/2° could result;

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SYNOPTIC MAPS OF SOLAR
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DERIVED FROM
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BOHLIN, J. D.,
N. R. SHEELEY, Jr. and
R. TOUSEY

BOHLIN, J. D.,

S. N. VOGEL,

J. D. PURCELL,

N. R. SHEELEY, Jr.,
R, TOUSEY and

M. E. VanHOOSIER

BOHLIN, J. D.,
D. M. RUBENSTEIN and
N. R. SHEELEY, Jr.

BRUECKNER, G. E. and
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SHEELEY, Jr., N. R.,
J. D. BOHLIN,

G. E. BRUECKNER,

J. D. PURCELL,

V. E. SCHERRER and
R. TOUSEY

TIMOTHY, A. F.,
A. S. KRIEGER and

G. S. VATANA
TOUSEY, R.s

J. -D. F. BARTOE,

J. D. BOHLIN,

G. E. BRUECKNER,

J. D. PURCELL,

V. E. SCHERRER,

N. R. SHEELEY, Jr,
R. J. SCHUMACHER and
M. E. VanHOOSIER

1975a

1975b

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REFERENCES

Structure of the Sun's Polar Caps in the Wavelengths
240-600 A, Paper given at COSPAR XVII (June 1974)
Sao Paulo, Brazil; in press for Space Research, XV,
A. C. Stickland, ed. (Akademie-Verlag, Berlin).

A Newly Observed Solar Feature: Macrospicules in
He II 304 A, Astrophys. J., 197, L133-L135.

The Sun's Polar Caps as Coronal Holes: Their Sizes,
Evolution and Phenomenology During the Skylab Mission,
Bull. Am, Astron. Soe., 7, 457 (revised abstract avail-
able on request).

The Fine Structure of the Solar Atmosphere in the Far
Ultraviolet, Solar Physics, 38, 133-156.

Extreme-Ultraviolet Observations of Coronal Holes,
Initial Results from Skylab, Astrophys. J., 194,
L115-L117.

Ha Synoptic Charts of Solar Activity for the Period of
Skylab Observations: May, 1973 - March, 1974, Report
vAG-40, World Data Center A for Solar-Terrestrial Physics,
NOAA, Boulder, Colorado 80302 U.S.A.

Observing Programs in Solar Physics During the 1973
ATM Skylab Program, Solar Physics, 27, 251-270.

XUV Observations of Coronal Magnetic Fields, Solar
Physics, 40, 103-121.

The Structure and Evolution of Coronal Holes, SoZar
Physics, 42, 135-156.

A Preliminary Study of the Extreme Ultraviolet Spectro-
heliograms from Skylab, Solar Physics, 33, 265-280.



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WORLD DATA CENTER A

for
Solar-Terrestrial Physics

Report UAG-51

SYNOPTIC MAPS OF SOLAR CORONAL HOLE BOUNDARIES

DERIVED FROM He II 304 A SPECTROHELIOGRAMS
FROM THE MANNED SKYLAB MISSIONS

by
J. D. Bohlin and D. M. Rubenstein

E.O. Hulburt Center for Space Research
Naval Research Laboratory
Washington, D. C. 20375 US.A.

November 1975

Solar-Terrestrial Physics, NOAA, Boulder, Colorado
and printed by

Published by World Data Center A for Sly
BZ

GZ
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NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION ZS
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UAG-6 "International Geophysical Calendars 1957-1969", price 30 cents.

UAG-7 “Observations of the Solar Electron Corona: February 1964-January 1968", price 15 cents.

UAG-8 “Data on BS a geornystcal Activity October 24-November 6, 1968", price (includes Parts 1
and 2) $1.75,

UAG-9 "Data on Cosmic Ray Event of November 18, 1968 and Associated Phenomena", price 55 cents.

UAG-10 "Atlas of Ionograms", price $1.50.

UAG-11 "Catalogue of Data on Solar-Terrestrial Physics" (now obsolete).

UAG-12 "Solar-Geophysical Activity Associated with the Major Geomagnetic Storm of March 8, 1970",
price (includes Parts 1-3) $3.00.

UAG-13 "Data on the Solar Proton Event of November 2, 1969 through the Geomagnetic Storm of November
8-10, 1969", price 50 cents.

UAG-14 "An Experimental, Comprehensive Flare Index and Its Derivation for 'Major' Flares, 1955-1969",
price 30 cents.

UAG-15 "Catalogue of Data on Solar-Terrestrial Physics" (now obsolete).

UAG-16 "Temporal Development of the Geographical Distribution of Auroral Absorption for 30 Substorm
Events in each of I0SY (1964-65) and IASY (1969)", price 70 cents.

UAG-17 "Ionospheric Drift Velocity Measurements at Jicamarca, Peru (July 1967-March 1970)", micro-
fiche only, price 45 cents.

UAG-18 "A Study of Polar Cap and Auroral Zone Magnetic Variations", price 20 cents.

UAG-19 "Reevaluation of Solar Flares 1967", price 15 cents.

UAG-20 "Catalogue of Data on Solar-Terrestrial Physics" (now obsolete).

UAG-21 "Preliminary Compilation of Data for Retrospective World Interval July 26 - August 14, 1972",
price 70 cents.

UAG-22 “Auroral Electrojet Magnetic Activity Indices (AE) for 1970", price 75 cents.

UAG-23 "U.R.S.I. Handbook of Ionogram Interpretation and Reduction", price $1.75.

UAG-24 "Data on Solar-Geophysical Activity Associated with the Major Ground Level Cosmic Ray Events
of 24 January and 1 September 1971", price (includes Parts 1 and 2) $2.00.

UAG-25 "Observations of Jupiter's Sporadic Radio Emission in the Range 7.6-41 MHz, 9 September 1968
through 9 December 1971", price 35 cents.

UAG-26 “Data Compilation for the Magnetospherically Quiet Periods February 19-23 and November 29 -
December 3, 1970", price 70 cents.

UAG-27 "High Speed Streams in the Solar Wind", price 15 cents.

UAG-28 "Collected Data Reports on August 1972 Solar-Terrestrial Events", price (includes Parts 1-3)
4.50

UAG-29 "Auroral Electrojet Magnetic Activity Indices AE (11) for 1968", price 75 cents.
UAG-30 "Catalogue of Data on Solar-Terrestrial Physics", price $1.75.

UAG-31 TAuroral Electrojet Magnetic Activity Indices AE (11) for 1969", by Joe Haskell Allen, Carl
¢. Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center,
Environmental Data Service, February 1974, 142 pages, price 75 cents.

UAG-32 "Synoptic Radio Maps of the Sun at 3.3 mm for the Years 1967-1969", by Earle B. Mayfield and
Kennon P. White III, San Fernando Observatory, Space Physics Laboratory and Fred 1. Shimabukuro,
Electronics Research Laboratory, Laboratory Operations, The Aerospace Corporation, E1 Segundo,
California, 90245, April 1974, 26 pages, price 35 cents.

UAG-33 "Auroral Electrojet Magnetic Activity Indices AE(10) for 1967", by Joe Haskell Allen, Car?
C. Abston and Leslie D. Morris, National Geophysical and Solar-Terrestrial Data Center,
Environmental Data Service, May 1974, 142 pages, price 75 cents.

UAG-34 "Absorption Data for the IGY/IGC and IQsY", compiled and edited by A. H. Shapley, National
Geophysical and Solar-Terrestrial Data Center, NOAA, Boulder, Colorado, U.S.A., W. R.
Piggott, Science Research Council, Slough, U.K.
Weltraumforschung, Freiburg, G.F.

sand K. Rawer, Arbeitsgruppe flir Physikalische
+» dune 1974, 381 pages, price $2.00.



WORLD DATA CENTER A

National Academy of Sciences
2101 Constitution Avenue, N. W.
Washington, D. C., U.S.A., 20418

World Data Center A consists of the Coordination Office

and seven Subcenters:

World Data Center A
Coordination Office

National Academy of Sciences

2101 Constitution Avenue, N. W.

Washington, D. C., U.S.A. 20418

[Telephone:

Glaciology:

World Data Center A:
Glaciology
U.S. Geological Survey
1305 Tacoma Avenue South
Tacoma, Washington, U.S.A. 98402
[Telephone: (206) 593-6506]

Meteorology (and Nuclear Radiation):

World Data Center A:
Meteorology
National Climatic Center
Federal Building
Asheville, North Carolina, U.S.A. 28801
[Telephone: (704) 258-2850]

Oceanography:

World Data Center A:
Oceanography

National Oceanic and Atmospheric

» Administration

Washington, D. C., U.S.A. 20235

[Telephone: (202) 634-7249]

Rockets and Satellites:

World Data Center A:
Rockets and Satellites
Goddard Space Flight Center
Code 601
Greenbelt, Maryland, U.S.A. 20771
[Telephone: (301) 982-6695]

Notes:

(1)

(2)
(3)

World Data Centers conduct international exchange of geophysical observations in accordance
with the principles set forth by the International Council of Scientific Unions. WDC-A is
established in the United States under the auspices of the National Academy of Sciences.
Communications regarding data interchange matters in general and World Data Center A as a
whole should be addressed to: World Data Center A, Coordination Office (see address above).
Inquiries and communications concerning data in specific disciplines should be addressed to

the appropriate subcenter listed above.

(202) 389-6478]

Rotation of the Earth:

World Data Center A:

Rotation of the Earth
U.S. Naval Observatory
Washington, D. C., U.S.A. 20390
[Telephone: (202) 254-4023]

Solar-Terrestrial Physics (Solar and
Interplanetary Phenomena, Lonospheric
Phenomena, Flare-Associated Events,
Geomagnetic Variations, Magnetospheric
and Interplanetary Magnetic Phenomena,
Aurora, Cosmic Rays, Airglow):

World Data Center A

for Solar-Terrestrial Physics
Environmental Data Service, NOAA
Boulder, Colorado, U.S.A. 80302
[Telephone: (303) 499-1000, Ext. 6467]

Solid-Earth Geophysics (Seismology,
Tsunamis, Gravimetry, Earth Tides,
Recent Movements of the Earth's
Crust, Magnetic Measurements,
Paleomagnetism and Archeomagnetism,
Volcanology, Geothermics):

World Data Center A

for Solid-Earth Geophysics
Environmental Data Service, NOAA
Boulder, Colorado, U.S.A. 83002
[Telephone: (303) 499-1000, Ext. 6521]



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