PB 151399-7

92o. 40 . 7

MEAN ELECTRON DENSITY VARIATIONS

OF THE QUIET IONOSPHERE

NO. 7 - SEPTEMBER 1959

BY J. W. WRIGHT, L. R. WESCOTT

AND D. J. BROWN

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March 3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and maintenance of the national standards of measurement and the provision of means and methods for making measurements consistent

with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials, devices, and structures; advisory services to government agencies on scientific and technical problems; invention and development of devices to serve special needs of the Government; and the development of standard practices, codes, and specifications. The work includes basic

and applied research, development, engineering, instrumentation, testing, evaluation, calibration services,

and various consultation and information services. Research projects are also performed for other government

agencies when the work relates to and supplements the basic program of the Bureau or when the Bureau's

unique competence is required. The scope of activities is suggested by the listing of divisions and sections on the inside of the back cover.

Publications

The results of the Bureau's research are published either in the Bureau's own series of publications or

in the journals of professional and scientific societies. The Bureau itself publishes three periodicals avail- able from the Government Printing Office: The Journal of Research, published in four separate sections,

presents complete scientific and technical papers; the Technical News Bulletin presents summary and pre- liminary reports on work in progress; and Basic Radio Propagation Predictions provides data for determining

the best frequencies to use for radio communications throughout the world. There Eire also five series of nonperiodical publications: Monographs, Applied Mathematics Series, Handbooks, Miscellaneous Publications,

and Technical Notes. A complete listing of the- Bureau's publications can be found in National Bureau of Standstrds Circular

460, Publications of the National Bureau of Standards, 1901 to June 1947 ($1.25), and the Supplement to National Bureau of Standards Circular 460, July 1947 to June 1957 ($1.50), and Miscellaneous Publication 240,

July 1957 to June 1960 (Includes Titles of Papers Published in Outside Journals 1950 to 1959) ($2.25); avail- able from the Superintendent of Documents, Government Printing Office, Washington 25, D. C.
NATIONAL BUREAU OF STANDARDS

40-7

April 1962

MEAN ELECTRON DENSITY VARIATIONS

OF THE QUIET IONOSPHERE No. 7 -September 1959

by

J. W. Wright, L. R. Wescott and D. J. Brown

Central Radio Propagation Laboratory

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referrt-d to in the open literature. They are for sale by the Office of Technical Services. V. S. l)ep;irt- ment of Commerce, Washington 25, I). C.

DISTRIBUTED BY UNITED STATES DEPARTMENT OF COMMERCE

OFFICE OF TECHNICAL SERVICES

WASHINGTON 25, D. C.

Price $1.50

MEAN ELECTRON DENSITY VARIATIONS

OF THE QUIET IONOSPHERE No. 7 - September 1959

by

J. W. Wright, L. R. Wescott and D. J. Brown

Central Radio Propagation Laboratory

ABSTRACT

The CRPL has initiated a program for large-scale

computation of electron density profiles from ionospheric

vertical soundings. Scaling is performed at field stations,

permitting computation of hourly profiles at the Central

Laboratory. These profiles are combined to form hourly

mean quiet profiles for each station and month. The results

of this program for the month of September are illustrated

graphically. This report is the seventh of a series illustrating the electron density variations in the mean quiet

ionosphere between latitudes 15 N and 50 N along the 75 W

meridian.

I

11

TABLE OF CONTENTS

PAGE

I. Introduction o 1

II. Description of Basic Data 3

III. Description of Graphical Representation 6

IV. Discussion and Applications of the Data 7

Acknowledgments 9

References 10

Hourly Vertical Cross Sections Along

75°W Geographic Meridian 1 Z

Isoionic Maps (150, ?,00, Z50, 300, 350, 400 km;

Nniax, hmax, Scat, Shmax, Shinf) 36

Electron Density vs. Time Curves (N(t)),

(Newfoundland, Ft. Monmouth, White

Sands, Grand Bahama, Puerto Rico) 17
I
1 MEAN ELECTRON DENSITY VARIATIONS

OF THE QUIET IONOSPHERE No. 7 - September 1959

by

J. W. Wright, E. R. Wescott and D. J. Brown

Central Radio Propagation Laboratory

I. Introduction

Part of the basic responsibility of the Central Radio Propagation

Laboratory is to gather ionospheric, solar, or other geophysical data

necessary in the pursuit of research leading to improvements in radio

communication and knowledge of the earth's upper atmosphere. The

existing network of ionospheric vertical sounding stations is an

important source of such data. Typically, the radio sounding data

directly provide observations of peak electron densities (corresponding to "critical" frequencies foE, foFl, foFZ), data on Sporadic E,

and certain derived propagation data such as maximum usable frequencies or MUF factors (Smith, 1939).

In fact, the vertical sounding is potentially capable of providing

the complete electron density profile of the underside of the ionosphere

(i. e. , below hmax FZ) and of providing a basis for extrapolation to

much greater altitudes. However, because a lengthy and difficult

calculation is required, little of this work had bt'cn doni- until quite

recently when techniques and computers have become available and

the exigencies of the ICY and satellite programs have made it imperative.

In the course of its development of facilities for electron density

profile calculations, tlie CRPL has succeeded in devising means by

which basic data for this purpose may be scaled by the individual field

stations, thereby decentralizing and simplifying the most onerous part

of the work. Through its own station network and those of the U. S.
2

Army Signal Radio Propagation Agency^ and through cooperation with

closely associated stations in other countries _, the CRPL has initiated

an extensive systematic data reduction program^ from which hourly

electron density profiles are being computed for the following stations:

Puerto Rico (NBS, January 1959)

Grand Bahamia Island (U. S. Army Signal Corps^ February 1959)

Fort Monmiouth, New Jersey (U.S. Armiy Signal Corps^ Feb. 1959)

White Sands^ New Mexico (U.S. Army SignalCorps^ March 1959)

St. Johns , Newfoundland (Def. Res. Tel. Establ. Canada^ June 1959)

Adak^ Alaska (U.S. Army Signal Corps ;, June 1959)

Okinawa, Ryukus (U.S. Army Signal Corps, June 1959)

Thule, Greenland (U.S. Army Signal Corps, July 1959)

Huancayo, Peru (January I9 60)

Talara, Peru (January I960)

Baguio, Philippines (February I960)

Affiliation and approximate date of initial participation in this program

are given in parentheses.

The hourly electron density profiles are extensively used in the

research programs of CRPL and are supplied directly to certain other

agencies as part of various research and practical activities. However,

in this comparatively early stage, broad dissemination of the computed

data is a some-what difficult problem.

In an attempt to make at least a summary of the results of the

programi widely and rapidly available, the CRPL has initiated the

present series of reports. These provide graphical representations of

the mionthly mean quiet hourly electron densities fromi certain of the

stations in the preceding list, from which a fairly clear picture of the

local ionosphere morphology may be obtained.

These reports contain N(h) data for the stations at Newfoundland,

Fort Monmouth, Grand Bahamia Island, White Sands, and Puerto Rico.

Pertinent facts concerning these stations are given in the following

table:
Table 1

Geomag. Coordinates Geog. Coordinates

fH Lat. Dip

St. Johns, Newf. 1.38Mc/s 58. 5°N 72°N 47°33'N 52°40'W

Ft. Monmouth, N.J. 1.46 51.7°N 71.5°N 4o"l5'N 74°0rW

White Sands, N.M. 1.30 41.2°N 60°N 32°24'N 106°52'W

Grand Bahama Island 1.30 37.9°N 59. 5°N 26°40'N 78°22'W

Puerto Rico 1.15 30°N 51.5°N 18°30'N 67°12'W

II. Description of Basic Data

True heights of reflection of radio waves are calculated from the

observed or "virtual" heights by the method of Budden (1954); this

method need not be described her e, but it should be pointed out that

full correction for geomagnetic field effects is made and that tlie

usual restrictions to monotonic profiles apply.

Tabulations of the mean electron density data at 10 km intervals

and certain related quantities are the bases for the graphs and charts.

A sample for the Puerto Rico September data is given on Pagi' 1 1 . The table on the following page identifies the quantities appearing on

the tabulation.
Quantity Units Remarks

Average Electron Density (N)

3 3 xlO = electron/cm

-5

( 1 on maps)

Body of table; given at each

10 km of height from the

lowest hmin to 950 km.

NMAX xlO^ = electron/cm

(10"5 on maps) The mean value of Nmax.

COUNT Count of the number of

profiles entering the miean.

HMIN Kilometers The average height of zero

or very lo-w electron density^

obtained by linear extrapolation of the electron density

of the individual profiles.

HMAX Kilomieter s The average height of maximum electron density, deter

mined by fitting a parabola

to the upper portion of the

individual profiles.

SCAT Kilonneter s One half of the half -thickness of the parabola best

fitting the upper portion of

the F-region profile. Approximates the scale height

near the true HMAX.

SHMAX 10 xlO = electrons/

(10

12

cm column

on maps)

Obtained by averaging the

integration of the individual

profiles between the limits

HMIN and HMAX.

SHINF xlO = electrons/

2 , cm column

-13

( 10 on maps)

The average total number

of electrons in a column to

infinity obtained by extrapolation of observed profiles

into the region above HMAX.

(See text. )
5

The following particular features of the tabulated data should be

noted:

A. Averaging process . Each hour of each day is identified with

its magnetic character figure^ Kp. For each hour, those days for

which Kp is less than 4+ are included in the "quiet" average. The

other days are similarly combined to form a "disturbed" average;

however, this rarely has physical significance because the number of

disturbed periods is usually small and the behavior of the ionosphere

during disturbed hours is not consistent. Thus^ graphs for these

latter averages are not presented here.

B. Determination of hmax. The nature of the "true height"

process is such that no direct measure of hmax F2 is obtained, the

virtual height at Nmax being imnneasurable. A useful procedure is

to fit the portion near hmaxFZ with a suitable curve and to determine

hmax from this curve. A parabola is quite satisfactory for this purpose; it is fitted to two of the highest true heights and the measured

value of Nmax(foF2).

C. Extrapolation of profiles above hmax. Before averaging, the

individual profiles are extrapolated above hmax by a Chapman distribution of 100 km scale height. This assumed model seems to agree

well with the few published measurements dealing with the profile of

the F region above hmax (Wright, I960). Extrapolation is necessary

in order to calculate homogeneous averages near hmax, and the average

profiles are, in fact, given to 950 km.

D. Integrated electron densities . The total number of elt-c Irons

in a unit column of the ionosphere between the effective bottom (hmin)

and hnnax is called Shmax; it is obtained by numerical integration of

the observed profiles between these limits. An estimate of the total

electron content to infinity, based upon the Chapman model, is called

Shinf. It is obtained by adding to Shmax tlie quantity Na = 2.82HNmax

where H is an (assumed constant) scale height for the region above

hmax. Current evidence (Wright, I960) indicates H = 1 GO km, is an

acceptable choice.
III. Description of Graphical Representation

The relative smoothness of mean quiet ionosphere data lends

itself to various kinds of graphical presentation which offer convenient aids to the visualization of the height, geographic, and temporal variability of the ionosphere. Included here are three such

graphical forms prepared from the tabulations described in Section II.

A. Vertical cross sections of the ionosphere along the 75 W

meridian. Pages 12 through 35 give, for each hour, a vertical cross

section of the mean quiet ionosphere along a nneridian section,

nominally the 75 W geographic meridian, for the month of September

1959. Contours are parametric in "plasma" frequency (f]\[) related to

electron density N by

12,400 f-^ (Mc/s) = N(electrons/cm ). The height of maximum electron density is represented by a dashed

line. Note that the vertical scale is expanded about 5. 5 times.

With the exception of White Sands, each of these stations is

reasonably close to the 75 W mieridian (see Table 1). There is the

possibility that some of the anomalies imposed by White Sands on

these contours are the result of the well-known longitudinal asymmietry

of the ionosphere.

B. Local timie vs. Latitude Maps . Another form of presentation,

useful for indicating the two-dimensional geographic variations of the

ionosphere, is that illustrated by the miaps of pages 36 through 45.

Here, for fixed levels in the ionosphere (150, 200, 250, 300, 350,

400 km), contours of electron density are drawn in the latitude vs.

local time plane. To the extent to which longitude anomialies are

negligible, these maps give also the longitude vs. latitude distribution

of electron densities at the indicated heights when it is noon over the

75 W meridian. Similar maps for the peak density, Nmiax; its height,

hmax; its characteristic thickness. Scat; the total electron content to

Nmax, Shmax; and the estimated total electron content, Shinf, are also

shown.
C. Electron density vs. time curves (N(t) curves) . The mean

quiet diurnal variation of electron density between 150 and 400 km

heights above the sounding stations is illustrated by these curves.

Dashed lines are used wherever the electron density at any height

falls below the peak density (i.e. when the height hmaxFZ falls below

the height for the curve in question.) Such electron densities are the

result of the extrapolations by the Chapman model discussed in

Section II C.

IV. Discussion and Applications of the Data

Mean quiet electron density data over wide geographic areas are

essential for application to numerous problems of both practical and

scientific interest. For example, the assessment of the radio refraction errors and Faraday rotation effects in satellite tracking requires

a knowledge of the electron density profile in the direction of the satellite or an estimate of the electron density at the satellite itself.

Alternatively these properties of the ionosphere, or estimates of the

total electron content in a column, may be measured by observations

from rockets and satellites, or from radar moon-echoes, and compared with ground-based observations of the kind shown here.

Frequently it will be necessary to use instantaneous density data

because of the considerable variability of the ionosphere about the

quiet mean. In such cases, the mean data are of value as a "reference

level" in the design of the experiment; for example, in the choice of

radio frequencies, satellite heights, antennas, etc.

Since electron density data represent virtually our only source of

continuous, widespread data on the earth's upper atmosphere, such

data also are essential to geophysical problems involving the electrical,

neutral, and magnetic properties of the atmosphere.
8

For example^ data on the vertical cross sections may be compared

with theoretical expectations for the mieridional height dependence of

the quiet ionosphere. Several workers (Hirono, 1955; Martyn 1956)

have investigated the equilibrium height (of hmax) for an ionosphere

controlled by diffusion^ height-varying electron loss rate^ and uniform

(or zero) vertical electron drift. The results are qualitatively in agreement with these observations in predicting a rise of hmax towards the

equator in daytimie and a reversal of this tendency at night.

The N(t) curves are perhaps the most physically significant representation of electron density data. The strong solar control at all levels

and the important perturbations of this solar control in the upper F

region may be easily seen.
Acknowledgments

We are indebted to Mr. A. H. Shapley for guidance in the

initiation of this work, and to Dr. H. H. Howe for the development of the computer programs upon which the whole system

heavily depends. This series of reports results from the com

bined efforts of the NBS Electron Density Profile Group,

including at various times L. R. Wescott, L. Hayden, D. J. Brown, F. J. Burmont, I. Ford, N. Moore, M. Durham,

G. Lira, under the direct supervision of G. H. Stonehocker.

The cooperation of the U. S. Army Signal Radio Propagation

Agency is gratefully acknowledged.
10

References

Budden^ K. G. , "A method for determining the variation of

electron density with height (N(z) curves)

from curves of equivalent height against frequency (h'(f) curves). Proc. Cambridge Conf.

on the Physics of the Ionosphere^ pp 33Z-339^

September 1954, Pub. by the Physical Society

(1955).

Martyn, D. F.

Hirono, M. ,

Smith, N. ,

Wright, J. W.

"Processes controlling ionization distribution

in the ionosphere," Aust. J. Phys. 9, pp 161-

165, March 1956.

"Effect of gravity and pressure gradient on

vertical drift in the F2 region," Rpt. on lono.

Res. in Japan, % No. 2, pp 95-104, (1955).

"The relation of Radio Sky\vave Transmission

to Ionosphere Measuremsents, " Proc. IRE, 27,

No. 5, pp 332-347, (1939).

"A model of the F region above hmaxF2,"

Journal of Geophysical Research, 65,

185-191, January I960.
11

^ a o

O- WMM

O O rWO » f

V •« ^ -fi « O r )» c^ooooooO(^«^-«tf^«»>n•oc^<

-* O •« *^ O

D X a X a • o I r I X :

t«tf>4P» ^Otf>(^fwm«4>r» r«J^•<^JP~M4•M.0•-•Artrf^(^fn49>Mr^t^MOOO'Mr^iO^«n4Ofr<^'4m^'rv^>m9<O'^«O•f«

•'OiA BA^O* -0^0««^-4al^rvSr>'0^ >. o — f^ « « •<

UJ hi O -* P r4r>» o>OOMMr<4«M<nfn4 4^^,f%o,o«r^P-^-^-r-r

i«in4l«« r»»»oo-nim<nrf% <^«Ol^(^(

- tf <f o o o -

X X O

O rw« rfi <r O «

> 4 « « « « r *-zMMNu. ooooooooo oooooooooooooooooooooooooooooooooooeoeeooooo

12 SEPTEMBER 1959

0000 75° W TIME

800

700

600

O) 500

liJ UJ3

^ 400

z

X

o

I 300

200 -

100 CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

\ I

I

VERTICAL SCALE 55 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RICO

J_ _i_ 50" 45° 40" 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20° 15°
13 SEPTEMBER 1959

0100 75* W TIME

800

700

600 —

tn 500

(T

llJ I-UJ3

^ 400

X

o

I 300

200 —

100 —

CONTOURS OF f

N

h-MAXIWUM

NEWFOUNDLAND FORT MONMOUTH

\ 1

I

VERTICAL SCALE 5.5 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RICO L _L -L. 50° 45"' 40" ^5" 30° 25° NORTH GEOGRAPHIC LATITUDE

20°
800

700

600

(/) 500

cru

Ul3

^ 400

X

CO

UlX 300

14 SEPTEMBER 1959

0200 75" W TIME

200

100

-N- CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

\ I I

VERTICAL SCALE 55 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RICO

[ , I . i \ 50° ^S" 40° 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20° 15'
15

800

700

600

cn 500

LlI UJ3

i^ 400

X

o

UJX 300

SEPTEMBER 1959

0300 TS** W-TIME

200

100 —

CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

I I

I

VERTICAL SCALE 5.5 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RICO L J_ _L. 50° 45° 40° 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20° 15°
16

SEPTEMBER 1959

0400 75" W TIME

800

700 -

600

en 500

cr

ill

iii 3

^ 400

IO

X 300

200 —

100 CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

VERTICAL SCALE 55 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA

JL

PUERTO RICO

50* 45° 40° 35" 30' 2

5'

NORTH GEOGRAPHIC LATITUDE

20* 15'
17 SEPTEMBER 1959

0500 75" W TIME

800

700

600 —

CO 500

OCUJH

UJ3

^ 400

X

o

LUX 300

200 —

100 —

CONTOURS OF fN h-MAXIMUM VERTICAL SCALE 5.5 X HORIZONTAL SCALE

NEWFOUNDLAND FORT MONMOUTH

I I

I WHITE SANDS GRAND BAHAMA

___! I L j_

PUERTO RICO

I 50° 45° 40° 35° 30° 25° NORTH GEOGRAPHIC LATITUOE

20°
li SEPTEMBER 1959

0600 75° W TIME

800 rT=^

700

600 —

(n 500

UJ

liJ 3

^ 4001—

I

C9

UJX 300

200

100

i

CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

\ I \

VERTICAL SCALE 55 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RICO

I I . ^ I 50° 45° 40° 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20° 15*
19

^1

800

700

600

en 500

ocUJ

hliJ 3

^ 400

X

COI 300

200 —

100

SEPTEMBER 1959

0700 75" W TIME

i

CONTOURS OF fN h-MAXIMUM VERTICAL SCALE 5.5 X HORIZONTAL SCALE

NEWFOUNDLAND FORT MONMOUTH

\ I I WHITE SANDS GRAND BAHAMA

I I \ .

PUERTO RICO

50° 45° 40° 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20°
20

SEPTEMBER 1959

0800 75" W TIME

800

700

600

W) 500

3

^ 400

X

o

UiX 300

200 —

100 CONTOJRS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

I I

I

VERTICAL SCALE 55 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RICO

_L _l_ JL. 50° 45° 40° 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20° 15°
21 SEPTEMBER 1959

09 00 75" W TIME

800

700

600

en 500

a:UJ

h-UJS

o_J^ 400

CD

LlJ 300

200

100 CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

I

VERTICAL SCALE 5.5 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RICO

I ^ \ i ^_l

50° 45° 40° 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20° 15"
22

SEPTEMBER 1959

1000 75° W TIME

800

700

600

CO 500

cr

lij

I

400 —

iLl I 300

200 —

100 CONTOURS OF fN h-MAXIMUM VERTICAL SCALE 55 X HORIZONTAL SCALE

NEWFOUNDLAND

\ i

FORT MONfylOUTH

I WHITE SANDS

^ I L.

GRAND BAHAMA

__J i__

PUERTO RICO

_! I 50" 45- 40° 35" 30" 25"

NORTH GEOGRAPHIC LATITUDE

20" I3«
800

700

600 —

en 500

QCUJ

I-UJ3

^ 400

X

UJI 300

200

100

23

SEPTEMBER 1959

HOOTS" W TIME

I

i

CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

\ i I

VERTICAL SCALE 5.5 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RICO

-i I I I 50° 45° 40° 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20° 15°
24

SEPTEMBER 1959

1200 75° W TIME

800

700

600

en 500

q:

UJ3

:^ 400

X

o

UJI 300

200

100 CONTOLfRS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

_L

VERTICAL SCALE 55 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RICO

I \ ^ ^ \ 50» 45» 40" 35" 30° 25" NORTH GEOGRAPHIC LATITUDE

Ze- is*
25

SEPTEMBER 1959

1300 75** W TIME

800

700

600 —

in 500

crui

UJQ

z

400 —

I-X

o

LUX 300

200 —

100

I

CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

I

VERTICAL SCALE 5.5 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RICO

I I . I 50° 45° 40° 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20° 15°
26

SEPTEMBER 1959

1400 75" W TIME

800

700

600

if) 500

q:UJUJ3

i^ 400

X

o

UlX 300

200

100 CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

\ I I

VERTICAL SCALE 55 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA

_L. -L.

PUERTO RICO

J I 50' 45» A<y 35" 30" 25*

NORTH GEOGRAPHIC LATITUDE

20* 19*
800

700

600

m 500

q:UJ

h-ui?

^ 400

o

LlI X 300

200 —

100 —

27

SEPTEMBER 1959

1500 75* W TIME

(

CONTOURS OF f

N

h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

I . I

VERTICAL SCALE 5.5 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RICO J \ I \ 1 _!_ 50° 45° 40' 35° 30" 25°

NORTH GEOGRAPHIC LATITUDE

20° 15°
28

SEPTEMBER 1959

1600 75° W TIME

800

700

600 —

en 500

a:UJ

hiij 3

:^ 400

Z

»-X

o

iLl X 300L_

200

100 CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

\ I I

VERTICAL SCALE 55 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA

_l_

PUERTO RICO

_. I 50' ^b' 40° 35" 30° 25" NORTH GEOGRAPHIC LATITUDE

20° IS'
29

SEPTEMBER 1959

1700 75" W TIME

800

700

600

ID

LlI H

UJ3

X

500

400 —

liJ I 300

200

100 CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

I ^ I

VERTICAL SCALE 5.5 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA

JL J_ JPUERTO RICO

J I 50° 45° 40° 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20° 15°
30 SEPTEMBER 1959

1800 75° W TIME

600

700 -

600

m 500

cr

LlJ (-ui3

ic 400

X

UJI 300

200

100 CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

I I I

VERTICAL SCALE 55 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RiCO

I i I . I \ 50° 45° 40° 35° 30° 2 5° NORTH GEOGRAPHIC LATITUDE

20° 15*
31 SEPTEMBER 1959

1900 75* W TIME

800

700

600

en 500

DCUJH

UJ3

^ 400

X

UJI 300

200 —

100 CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

VERTICAL SCALE 5.5 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA

I i \ ^

PUERTO RICO

I 50° 45° 40° 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20° 15°
800

700

600

32 SEPTEMBER 1959

2000 75° W TIME

if) 500

OC

LiJ \-UJ3

^ 400

X

UJX 300

200 —

100 —

CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

I I I

VERTICAL SCALE 55 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RiCO

_L. -L. _l_ 50° 45° 40° 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20° 15'
33 SEPTEMBER 1959

2100 75* W TIME

800

NEWFOUNDLAND FORT MONMOUTH

I I \

VERTICAL SCALE 5.5 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RICO

_L _!_ 50° 45° 40° 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20° 15"
34

SEPTEMBER 1959

2200 75° W TIME

800

700

600

(A) 500

CC

LlI

X

400

I 300

200

100 CONTOURS OF fN h-MAXIMUM

NEWFOUNDLAND FORT MONMOUTH

\ I I

VERTICAL SCALE 55 X HORIZONTAL SCALE

WHITE SANDS GRAND BAHAMA PUERTO RICO

\ I i i i I 50° 45° 40" 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20° 15'
35 SEPTEMBER 1959

2300 75* W TIME

800

700

600

CO 500

CCUJH

LiJ 3

^ 400

X

C£

UJX 300

200 —

100

-N- CONTOl^S OF fN h-MAXIMUM VERTICAL SCALE 5.5 X HORIZONTAL SCALE

NEWFOUNDLAND FORT MONMOUTH

I I I

WHITE SANDS GRAND BAHAMA

__l I L _u

PUERTO RICO

-L. 50° 45° 40° 35° 30° 25° NORTH GEOGRAPHIC LATITUDE

20° 15°
N" 50

NF45

FM1^-

35

WS30

GBh

25

20-

PR

36

ELECTRON DENSITY AT 150 KILOMETERS

SEPTEMBER 1959

1500

- I / 1 I I I I L

00

75° W TIME

CONTOURS' cTtTS

• ^-^ « 10"*
37

N" 50

NF45

FMTC35

WS30

GBl25

20-

PR

ELECTRON DENSITY AT 200 KILOMETERS

SEPTEMBER 1959

151 I I I 1 I 00

J 1 I L

75° W TIME

00

CONTOURS --T^ X

10"*
38

N" 50

GBI

ELECTRON DENSITY AT 250 KILOMETERS

SEPTEMBER 1959

75° W TIME

8 00

CONTOURS'

^ X 10

'
39

ELECTRON DENSITY AT 300 KILOMETERS

SEPTEMBER 1959

I

75* W TIME CONTOURS--^ X I0~*
40

ELECTRON DENSITY AT 350 KILOMETERS

SEPTEMBER 1959

GBI

TS** W TIME

8 00

CONTOURS' r^ X lO"'
41

ELECTRON DENSITY AT 400 KILOMETERS

SEPTEMBER i959

GBl

75** W TIME CONTOURS: r^ X

10"®
42

GBI

MAXIMUM ELECTRON DENSITY

NMAX

SEPTEMBER 1959

75° W TIME CONTOURS* —^ « 10' cm ^
43

HEIGHT OF MAXIMUM ELECTRON DENSITY

HMAX

SEPTEMBER 1959

GBl

5° W TIME

00

CONTOURS = Km
44

QUARTER THICKNESS OF F-REGION PEAK

SCAT

SEPTEMBER 1959

GBI

15 J A \l I

I ^'* — -L-^ I I I t 1 1 1 1 1 I II 1 L 00 06 12 00

7 5° W TIME CONTOURS KfT<
45

ELECTRON DENSITY INTEGRATED TO HEIGHT

OF MAXIMUM ELECTRON DENSITY

SHMAX

SEPTEMBER 1959

GBI
46

ELECTRON DENSITY INTEGRATED TO INFINITY

SHINF

SEPTEMBER 1959

GBI75° W TIME

CONTOURS ' -^col «I0"'
25

47

N(t) NEWFOUNDLAND SEPTEMBER 1959

FIXED HEIGHTS IN Km

20

i

I 15

lOg

X

V

cn

O

cc

I-<j

UJ

_iUJ
25

20

o

15

48

N(t) FT MONMOUTH SEPTEMBER 1959

FIXED HEIGHTS IN Km

z

UJo

z

o

(ES 10

_jUJ
49
50
51

N(t)PUERTO RICO SEPTEMBER i959

FIXED HEIGHTS IN Km
IJ. S. UKPAHIMIM UF CUMMLKLL

Luther H. Hodge.s, Secretary

iNATIONAL RURKAU OF STAN DA R OS

A. V. Astin, director

THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its major laboratories in Uushington, D.C, and

Boulder, Colorado, is suggested in the following listing of the divisions and sections engaged in technical work.

In general, each section carries out specialized research, development, and engineering in the field indicated by

its title. A brief description of ttie activities, and of the resultant publications, appears on the inside of the

front cover.

r

WASHINGTON, D.C.

Klectricity. Resistance and Keactance. Electrochemistry. Electrical Instruments. Magnetic Measurements.

Dielectrics. High Voltage.

Metrology. Photometry and Colorimetry. Rcfractometry. Photographic Research. Length. Engineering Metrology.

Mass and Scale. Volumetry and Densimetry.

Heat. Temperature Physics. Heat Measurements. Cryogenic Pliysics. Equation of State. Statistical Physics.

Radiation Physics. X-ray. Radioactivity. Radiation Theory. High Energy Radiation. Radiological Klquipment.

Nucleonic Instrumentation. Neutron Physics.

Analytical and Inorganic Chemistry. Pure .Substances. Spectrochemistry. Solution Chemistry. Standard Refers ence Materials. Applied Analytical Research.

Mechanics. Sound. Pressure and Vacuum. Fluid Mechanics. Engineering Mechanics. Rheology. Combustion

Controls. Organic and Fibrous Materials. Rubber. Textiles. Paper. Leather. Testing and Specifications. Polymer Structure. Plastics. Dental Research.

Metallurgy. Thermal Metallurgy. Chemical Metallurgy. Mechanical Metallurgy. Corrosion. Metal Physics. Electrolysis and Metal Deposition.

Mineral Products. Engineering Ceramics. Class. Refractories. Enameled Metals. Crystal Growth. Physical

Properties. Constitution and Microstructure. Building Research. Structural Engineering. Eire Research. Mechanical Systems. Organic Building Materials. Codes and Safety .Standards. Heal Transfer. Inorganic Building Materials. Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Mathematical Physics. Operations Research. Data Processing Systems. Components and Techniques. Computer Technology. Measurements Automation.

Engineering Applications. Systems Analysis.

Atomic Physics. Spectroscopy. Infrared Spectroscopy. Solid State Physics. Electron Physics. Atomic Phy«ic«.

Instrumentation. Engineering Electronics. Electron Devices. Electronic Instrumentation. Mechsnical Instru- ments. Basic Instrumentation. Physical Chemistry. Tliermochemistry. .Surface Chemistry. Organic Chemistry. Molecular Spectroscopy. Molecular Kinetics. Mass Spectrometry.

Office of Weights and Meastres. BOULDER, COLO.

Cryogenic Engineering, (pyogenic Equipment. Cryogenic Processes. Properties of Materials. Cryogenic Technical Services. Ionosphere Research and Propagation. Low Frequency and Very Low Frequency Research. Ionosphere Hesesrrh.

Prediction Services. Sun-Earth Relationships. Field Engineering. Radio Warning Services. Vertical Soundings Research. Radio Propagation F.ngineering. Data Reduction Instrumentation. Radio Noisr. I amnents.

Iropospheric Analysis. Propagation-Terrain Effects. Radio-Melrorolopv. Lower Aii Radio Standards. High Frequency Electrical Standards. Radio Rro rvice. H

.lis. Atomic Fre()uenry and Time Interval StandiU'ds. Electronic ( .1 n Center. Microwave! (Circuit Standards. Radio Systems. Applied Electromagnetic Theory. High Frequency and Very High Frequency

Research. Antenna Research. Navigation Systems.

Upper Atmospliere and Space Physics Ilnn«r Aimr>ank»» «?.* Tm.... Pi.v. Scatter. Airglow and Aurora. lono

>l>>dulstion

lysics. llppor Atmosphere

spheric Radio Astronomy.

.. I. unti K*« n«iih<*rr iiKr
NBS