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9

AFCRL-700422 27 JULY 1970 ENVIRONMENTAL RESEARCH PAPERS, NO. 327

AIR FORCE CAMBRIDGE RESEARCH LABORATORIES L. C. HANSCOM FIELD. BEDFORD. MASSACHUSETTS

Auroral Oval Plotter and Nomograph for Determining Corrected Geomagnetic Local Time, Latitude, and Longitude for High Latitudes in the Northern Hemisphere

JAMES A. WHALEN

D D C KfEGXmJE A 1CT 27 1970

c United States Air Force

3/

This dooumtnt ha« btm ipproytd for public its distribution it unlimitod.

MM MMJ

Qualifiod roquMton may obtain additional copiai from tba Dafanta Documtntation Cantar. All othart should apply to tht daarinflhouaa for Fadaral Sdantific and Tachnieal Information.

AFCRL-70 0422 27 JULY 1970 ENVIRONMENTAL RESEARCH PAPERS, NO. 327

IONOSPHERIC PHYSICS LABORATORY PROJECT S631

AIR FORCE CAMBRIDGE RESEARCH LABORATORIES L. C. HANSCOM FIELD, BEDFORD, MASSACHUSETTS

Auroral Oval Plotter and Nomograph for Determining Corrected Geomagnetic Local Time, Latitude, and Longitude for High Latitudes in the Northern Hemisphere

JAMES A. WHALEN

This document has been approved for public release and sale; its distribution is unlimited.

United States Air Force

Abstract

A nomographic computer is presPnte d whic h gr·aphically converts ge ographic al

coordinates and universal time into g eomagnetic coo t·clinatcs and geom agne ti lo al

time in the Correcte d Geomagnetic syste m of Hultq\"i s t , Th computer is fot· m u ­

late d as a map of high latitudes in t he North t·n He m isph r·e on whi h the position

of the auroral oval can be projecte d dit·ectly for any tim e o f day, fo r any magne ti ·

activity, with account being take n of s easonal \'a t· iation o f t he geomagn ti c local

time coordinate , Instructions for its us e , dis c uss ion o f its a ccu racy, and c xa mplc·s

of its applic ation are given.

iii

Contents

1. INTHOm CTION

2. ciroici: OK COORDINATKS

<. CG. LOCAL TIME CONVENTION

». DESCRIPTION OK A« ROKAI. OVAI. PLOTTER

4. 1 Map of the Northern Hemisphere at High Latitudes (see Insert which contains transparent map and page of directions)

4.2 Auroral Oval Rot in C.G. Latitude and CO. Local Time (Appendix A)

5. ACCKRACY

(i. APPLICATIONS

ß, 1 Constant Geographic" Path 6,2 Constant C.G. Local Time (;.:< Accelerated Local Time: The Circum-Oval Flight

\CKNOWLEDGMENTS

REFERENCES

APPENDIX A - Auroral Oval Plots

1

2

4

4

4

5

5

6

6 6 9

11

13

Al

Auroral Oval Plotter and Nomograph for Determining Corrected Geomagnetic

Local Time,Latitude, and Longitude for High Latitudes in the Northern Hemisphere

I. INTROINCTION

The coordinates of geomagnetic latitude and geomagnetic local time form a

very useful basis for ordering geophysical phenomena which depend on the solar-

magnetospheric interaction. Thes< :ire the coordinates of the auroral oval and

many other phenomena, and form the logical basis in which to map the boundary

interactions between magnetosphere and ionosphere. The conversion to these coordinates from geographic coordinates and universal

time is tedious even for observatories with fixed locations. For a moving observa-

tory with rapidly changing location, the practical problem of coordinate transforma-

tion particularly in real time is almost insurmountable without the use of an on-line

computer. This is the case for the AFCRL Airborne Ionospheric Observatory, an

NKC-135 jet aircraft instrumented with an ionospheric sounder, photometers, and

all sky cameras (Buchau et al, 1969).

Thus the Auroral Oval Plotter has evolved out of the necessity foi rapid coor-

dinate transformation, and is a descendant of Akasofu's mechanical auroral oval

model (Private Communication, 1968). Use of the Plotter has made it possible to

approach auroral observation by conceptually navigating in the auroral oval frame

of reference.

(Received for publication 10 July 1970)

2

:!. CIIOICf. OF .OOROI~ . .\ TE

The magne tic field of the earth is a pproximately that of a dipole , yet the de­

partures from the dipole particularly in polar regions are significant enough to have

inspired a large va l'i d y o f c oordinate syste ms. Pendorff (1968) gives a surv~y of

many o f the m.

This report adopts the corrected geomagnetic (C. G.) system of Hultqvist (1958a,

1958b), using the coordinate s computed by Hakura (1965). The details o f the fo rmu­

la tio n of the C . G. syste m appear in the above refe r e nc es and will not be treate d

he r e .

This sys te m has ga ined wide acc eptance by many workers, a nd the Feldste in

a nd Sta rkov (1 967) auroral oval is formulated in it. Although derived from m e asure ­

m e nts o f the e arth's magnetic field made in 1945, it has been suc cessfully applied

to the rganization of auroral and r e lated data for a long pe riod of time, Table 1

l is ts e xamples o f t~e uses of the C. G. system including: date of the obse r vations;

phenom e na s tudie d ; he misphere, north or south (N+S m eans data from both he mi­

s phe r es a r e combined to form a consistent whole); whic !-1 of the C. G. coordinate s

r e m ployed (latitude, longitude, or longitude -local time , the latter two be ing

inte r· -de pendent ).

The m ost r ecent observa tions find that the C. G. latitude of the noontime aurora

is the sa m e in 1969-1 970 (Buc hau e t al, 1970) as it was in 1957-1958 (Feldste in and

Starkov, 1967 ) as we ll as in 1963 (Sandfo r d, 1968), 1967 (Buc hau e t al, 1969), a nd

in 196 8 (Wha l e n e t a l , 19 70 / . This indicates the stability of the C. G. coordin te

syste m - a uro ral phenome na r ela tionship whic h is of s pec ific inte rest to this work.

The~e meas ure m ents, couple d with the magnetic m e asur e m e nts pe rforme d as early

as 1932, indi ate a ve ry desirable s tability of the C .G . s ystem spanning nea r ly

fo ur decades .

In a dd itio n , the C . G. syste m has been compared with othe r s yste ms and found

s upe r ior. The tests have been the plotting of the da ta in ea c h system, a nd i n each

one the C . G . syste m has been found to be the m ore cons istent in o rde ring the data.

T a ble 1 s hows those ins ta nces noted by asterisk; the syste ms compared are the

au r·o r·a l a nd ecce ntric dipol e in the cas e o f Sandford ( 1963 ), nd cente r e d dipole for

the others .

o com pre he nsive co mparison of geoma gne t ic s ys te m s is a tte mpte d he r e, but

these examples do illus t rat e the bas is fo r c hoosing one syste m over another . In

addition, T a ble 1 s hows tha t Hultq vis t set a comme nda ble example i n ass uming the

burde n of proving the value o f the C . G. sys te m whi c h he o rigina ted.

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3. C.G. LOCAL TI\IE CO'J\'E'JTIO\

The definition of geomagne tic loc al time is quite arbitrary, since t here is no

regularly obse rvable geomagne tic time -refere nce (although Hultqvist and Gustafsson,

1960, de te rmine d o ne a pplicabl e to storm -time c onditions). This work adopts the

"equal te mpe r ed " time conve ntion of Mc Nish (1936) which is widely a cc e pted and

ve ry conve nie nt. In this conve ntion, the C. G. local m idnight meridian is defined

as tha t whic h passes thro ugh the anti-subsolar point; C. G. local tim e is computed

fr·om that m e ridian on the basis of one hour be ing equal to 15° of C. G. longitude .

With this convention, a particularly simpl e rel a tionship e xists be tween ( 1) a

m a p o f the e arth in C. G. l titude and C.G. longitude , nnd (2) the r e ference fram e

of C. G. l a titude and C. G . local t im e :

One is a l"igid fr·ame of r e fe r e nce moving within the fra m e of the othe r with the

passage o f universa l time (U. T. ). Motio n is in the di rec tion of C. G. longitude /

C . G. lo al time . C. G. lo al time is thus de fined a t all points o f the map s i multa ­

neous ly a t any instant o f U, T., by the alignme nt of the C. G. local midnight m e rid­

ian with the a nti- s ubsola r point a t that value of U. T,

l. UF:SCIUI•TIO\ Of -\IJilOIHL 0\'.\L PLOTTEil

The Auru ral Oval Plotte r o pe rates a c cording to the fore going princ iple , and

co ns ists o f two fram es of reference:

-l.l \1••1• of tlw \orthern llemi ><Jihe re at lligh Latitudes ( :;f•e ln:;t• rt "hil·h contuins truns parent map and page of directions ).

This m ap e nt itl e d "Ge ographic Coordinates Plotted in Corre cted Geomagne tic

Coo r·d inate s " is a polar azimuthal equidistant projection in C. G. latitude (cl>c) and

C . G . longitude ( \ ) a bout t he C. G. pole (at B0°N B1°W ge ographic ). The C . G . c

po la r· - coo r·din a te g rid is not plotted e xpl ic itly, although the cir c les of co ns tant C. G.

la titude a nd r a dii o f constant C. G. longitude can be constructed from the fidu c ial

ma r· ks a nd fro m the val ues o f Ac a nd ci>c at the pole and at the margin of the map.

Ins tead , the grid of geographic latitude and geographic longitude is explic itly shown

togethe r with the appr·o xi m ate land mass es and the locations of some points of inter ­

est. This avo ids the confusion of two overlapping grid sys terns which, in any case ,

are unnec ess a ry fo r the co nve rsion from geographic coordinates and U. T. to C. G.

la titude and C. G. local time .

4.2 Worul Oval I'loi in V.M. I.iiliiud«- und CM. l.wul 'IW ( \p|M*ndU \)

This is the oval of Feldstein and Starkov (19«7) sliuwn in nine versions, one

for each value of magnetic index Q from 0 to 8. The three versions of the "UT

Seale"'marked "Dec.", "Mar.-Sept.". and "June" are correct for winter solstice,

equinoxes, and summer solstice, respectively. They arise from tin* Hcasonul

variation in the C G. longitude of the anti-subsolar point for a given I'.T. This

point moves north or south with season at constant geographical longitude, which

is not in general constant C.G. longitude but varies in the manner shown.

The map functions as an overlay of th? oval plot for the desired value of Q,

and pivots about an axis through the common pole. This pole is indicated by the

double circle which in addition is labelled '^,90 " on the map. The map makes

one complete rotation per day corresponding to the rotation of the earth; for any

value of U.T. its position is determined by aligning that value of I'.T. on the ap-

propriate "U.T. Scale" (on the oval plot) with the "U.T. Index" (the dotted line on

the map). This places the C.G. local midnight meridian through the anti-subHolar

point at this value of I'.T., and so defines C.G. local time everywhere as de-

scribed earlier. C.G. latitude and C.G. local time for any point on the map are

read directly from the oval plot on which the map is superimposed. In addition,

the position of the oval is given with respect to any point on the map. (An approxi-

mate U.T. scale sufficiently accurate for many purposes is the C.G. local time

scale as read directly from the oval plot at.the point of the arrow on the U.T.

Index.)

5. \(:tiR\(:Y

The precision with which the C.G. coordinates can be read from the nomograph

exceeds their inherent uncertainty which Hultqvist (1958b) estimates to be of the

order of 50 km. Feldstein and Starkov (1967) estimate that the oval boundaries

have an uncertainty of about 1.0 of latitude. The oval itself is derived from ob-

servations averaged over C.G. local time intervals of _^2 hours observation.

An additional uncertainty arises from the possible variation of the latitude of

the noon aurora with season, or more specifically with "tilt angle" between mag-

netic axis and earth-sun line. Fukushima's (1965) work indicates that in the Wes-

tern Hemisphere during summer, for example, the latitude of the noon sectors of

the ovals may be displaced as much as 5° poleward of the values presented here.

Maehlum (1968) finds additional evidence of this displacement from satellite

observations.

6

6 . . \I"PUC.\Tit.l~ :i

The Aur·o r a l Oval Plotte r has e volved ove r the past three ye ars c hie fly throug h

airbo rne stud i s. It is, of course , not l im ited to this use but has applic:ation to

gro und-based s tudi es and to the c onceptualization of the oval as a whole . The ova l

fo r· Q =3 is a typical configuration of use in e stimating the location of the au r o ra i n

gene r al .

In fl ight plann ing the plotte r c an optimize aircraft naviga tion in the ova l

fr·a m e o f r·e fe r e nce give n the o the r constraints (a ircraft pe rfo rm:1nc e , geography ,

geopolitic s, s un, m oon, a nd of c ourse the phe nomena to be studied).

During flight one c an monitor the expected position of the ova l as a n a id i n

m a inta ining his o rie ntation with respect to the aurora, which i s frequ ntl y v0r·y

confu s ing if the flight path is a t a ll irre gula r. One can r a pidly de te r mine whe thc •·

the au rora is northorsouth ofthe e xpe c te d position, and he nce if c onditions a r e qu iC'l

o r dis tu1·be d a nd whe ther o r not this necessita tes c ha nges in flight pla n. In a dd i ­

tio n it is a n aid in c hoosing be twe en alte rnatives whe n c ha nges in fl ig ht pl a ns a r·c

ne c e s s ary f0 r ope rational r e asons.

Three basic flight patte rns will be illustrate d : c ons tant geographic pa th, con­

s ta nt loc al time, accele rated loc al time. E xamples co m e fro m a c tua l da ta flight s

planne d , m onitore d , and analyze d by the aid of the auro r al plotte r.

b. I Con,;lunl l ;t'O(.!ruJthic l•uth

T he s i m pl st fli ght path is tha t \vhi c h patrols bac k and forth along a fixe d geo ­

g r·aph i a pa ll-.. Figur·e I (lower portio n) shows a geographic m a p (no t pa r't of the

uval plo tte r desc ribe d in th is wor h), o n whic h the ~ligh t le gs are a ctually coinc ide nt

but a r·e s how n d isplaced fr·o m o ne a no the r in orde r to r e s o lve the m in ti m e . The

a ctual rout o r igina te d and te n11ina te d a t Goose Bay, moving alte rnate ly north a nd

south geo g r a phic a lo ng a cons tant geographic lo ngitude. The times, give n at U . T . ,

ide ntify s pecific po ints in the two c oordinate s ystems . F igure 1 (upper por tion) is

the p lo t of this fligh t in . G . latitude and C. G. local time superimpose d on the Qo: 3

ova l a s g r a phic a lly tra c e d on the oval plot using the C . G . map described earlie r .

6.2 t:un:<lunl Lf.. l.ocul Time

An e xample of a constant C . G. local t1me flight is the flight of 8 January 1970

s hown in Figure 2. This flight originated in Eie lson AFB, Alaska, and terminated

in Keflavik, Iceland . It sta yed within 2 hours of C. G. local noon fo r a duration of

approxi mate ly 10 hours , simultane ously scanning in latitude. C . G. local midnight

flights be tween Labrado r and Alaska have maintained the midnight sector of the

oval for similar pe riods of time. However since the midnight oval is at lower

18 APRIL 69

Figure 1

^"•^^O 0Ö30-L S

r;o

,7- / -r ■- r

8 JAN 70

Figure 2

latitudeB where the velocity of the earth Is greater, the aircraft ran make only very

limited latitude scans, the greatest component of its velocity being required to keep

up with the rotation of the earth.

6.3 WrH.-riUfd (••(•. Lor«! Time: The • ir.um-OMil Kllifhl

Flying in the direction of the rotation of the earth accelerates im-al time. Fly-

ing along the auroral oval in this sense affords the opportunity of examining its

continuity over extended sectors in a manner not possible from ground xtationn.

The navigation problem of computing the intersection of the path of the oval over

the earth with that of a rapidly moving aircraft is in general quite complicated, but

greatly simplified by use of the auroral oval plotter. With its aid it has been pos-

sible to achieve a flight completely around the oval (less about one hour). This

flight (5 January 1970 shown in Figure 3) which originated in Keflavik, Iceland,

and terminated in Eleison, Alaska, succeeded for the first time in examining the

continuity of the oval as a whole (Buchau et al, 1970).

10

5 JAN 70

Figure 3

11

Acknowledgments

The author wishes to thank the following: 8, -I. Akasolu is the originator of

the mechanical rotating oval model of which this plotter is a lonceptual ck'sc-end-

ant. J. Buchau and R. A. Wagner have given invaluable aid throughout the entire

evolution of the Auroral Oval Plotter into a working instrument.

Preceding page blank ia

References

Buchau, J., Whalen, J. A., and Akasofu, S.-I. (1969) Airborne obsc-rvation of the midday aurora J. Atmos. Terr. Phys. 31:1021-1026.

Buchau, J., Whalen, J.A,, and Akasofu, S.-I. (1970) On the Continuity of the Auroral Oval, submitted to J. Geophys. Res.

Feldstein, Y. I. and Starkov, G. V. (1967) Dynamics of auroral belt and polar geomagnetic disturbances Planet. Space Sei. 15:209-229.

Fukushima, N. (1965) Seasonal change of auroral zone in corrected geomagnetic latitudes Rep. lonosph. Space Res. Jxpan 19:367-370.

Gustafsson, G. (1967) On the orientation of auroral arcs Planet. Space Sei. 15:277-294.

Hakura, Y. (1964) Patterns of polar cap blackouts drawn in geomagnetic coordin- ates corrected by the higher terms of spherical harmonic development Rep. lonosph. Space Res. Japan 18:345-365. —

Hakura, Y, (1965) Tables and maps of geomagnetic coordinates corrected by the higher order spherical harmonic terms Rep. lonosph. Space Res. Japan 19:121-157.

Hultqvist, B. (1958a) The spherical harmonic development of the geomagnetic field, epoch 1945, transformed into rectangular geomagnetic coordinate systems Ark Geofy. 3:53-61.

Hultqvist, B. (1958b) The geomagnetic field lines in higher approximation Ark. Geofys. 3:63-77.

Hultqvist, B. (1959) Auroral isochasms Nature 183:1478.

Hultqvist, B. and Gustafsson, G. (1960) On i e magnetic time dependence of the auroral zone currents J. Atmos. Terr. Phys. 19:246-259.

Maehlum, B. N. (1968) Universal-time control of the low-energy electron fluxes in the polar regions J. Geophys. Res. 73:3459-3468.

14

R«f«r«nc«t

Mayautl, I». N. (1900) Un Noveui Systfius de Ctx>rdonncc8 Magnetiguea jiour I'Kiiulf dp la Haute AtmoHphorc: lea Coordonnoca 'le 1'anncau Equatorial Ann. Gi-i>pliy>?iquf 1(5:278-288.

McNlHh, A.G. (1936) Goomuf^ietic coordinatos for the entire earth Terr. Magn. 41:37-43.

IVnrulorff, H. (1988) The Antarctic lonoaphere Part A: Survey and Baaic Informa- tion, Antarctic Research and Data Analyaia Scientific Reporf No. 28, AVSSD- IRIS3-68-CR, Contract NSF-C-515, Office of Antarctic Programs. National Science Foundation, Wash., D.C,

Sandford, B. P. (1968) Variations of auroral emissions with time, magnetic activity, and the solar cycle J. Atmos. Terr. Phys. 30:1921-1942.

Whaien, J.A,, Buchau, J., and Wagner, R.A. (1970) Noontime Aurora, Discrete and Continuous, Detected by Airborne Ionospheric and Optical Measurements, submitted to J. Atmos. Terr. Phys.

Al

Appendix A Aursrol Oval Plots

A'i

AURORAL OVAL

18 h

C«rr«(l«4 G«»»«f .»tic L»c«l Tta«>

\A

AURORAL OVAL

C«"«c<t4 0«»«««««< c Lacal Tia*^

H06

A4

AURORAL OVAL

C«rr««tt4 0«*a««*«*>c L»c«l Tia«!

A5

AURORAL OVAL IFcUllti« 19671

C«rrt(t«4 OtaaafMttic L»c«l TiaO

« LoMy««

A6

AURORAL OVAL C*rr«fl«4 Gti>««*«*ic L««al Ti««i

-06

A7

AURORAL OVAL

C*rr«(««4 0«*B«f iit*<c L*<«l Ti«M

AH

AURORAL OVAL

C«rr«tUtf 0***««««lic L«c«l Ti««l

18-

A!)

AURORAL OVAL ('•Itftiti« i««T)

C*rr«ct«4 G«*a««it«*ic Lactl T.»«!

AK)

AURORAL OVAL ('•IJittiii i9»n

18-

C«rr«tlt4 0«»a«t***>( Ltcal Tia«)

-06

WRKI.TIONS iso'e^.-

DIRECTION SHEET •wc 'Ait..

he transparent

rdinates,' »U^j^oth

izo»*

and su

C*PC

GEOGRAPHIC COORDINATES pioM.d i« CORRECTED GEOMAGNETIC COORDINATES

DIRECTION SHEET

INHKCTIONS

The AUHOKAL OVAL PLOTTKH conHlst« of two clenu-ntH: (I) the tranHpuront

mup titled 'GeoKraphlc Coordinates plotted in Corrected Geomagnetic CoordinateH,"

which is enclosed in this envelope; and (2) one of the nine auroral oval plots. Both elements have been constructed to rotate about the same axis (the center point of the C.G. poles).

Plollrr Wi'mbK

1) Lay the transparent map over an auroral oval plot. Adjust them so that the C.G. poles on both coincide exactly. (The C.G. poles are the crosses at the center of the double circles marked ♦90 on the map.)

2) Place a pin or tack through the center points of both crosses to serve as an axis of rotation.

The U.T. PoHilion

Rotate the map until the U.T. Index (dashed line on the map) aligns with the desired time on the U.T. Scale (near the center of the oval plot). The C.G. local time (and C.G. latitude) can then be read from the oval plot for any point on the map. For example, aligning the U.T. Index with 20 on the U.T. Scale marked l)ec. places the oval at the correct position with respect to the earth at 20 U.T. for winter solstice (Fairbanks, Alaska (FA on the map) is seen at 08:32 C.G. local time J.

The U.T. Scales marked Mar. Sept. and June correspond to the equinoxes and summer solstice, respectively.

Unclassified Securiry Classificarion

r DOCUMENT CONTROL DATA · R&D , (.~.curily classificotion of till•. body of ab51tacl and index in;; unnotalion mu.<t be rnt•red when the ovno/1 report is clauifi•d)

I. ORIGINATING ACTIVITY (Corporal< aulhor) 2a. RCPORT SECURITY CLASSIFICATION

Air Force Cambridge Research Laboratorie s (CRP) Unclassifie d L.G . Hanscom Field 2u. GROUP

Bedford, Massachusetts 01730 1 REPORT TITLE

AURORAL OVAL PLOTTER AND NOMOGRAPH FOR DET ERMING CORRECTE D GEOMAGNETIC LOCAL TIME, LATITUDE, ~ND LOGITUDE FOR HIGH LATITUDES IN THE NORTHERN HEMISPHERE 4. DESCRIPTIVE NOTES (Type of report and incl115ivt dolts)

Scientific. Interim. ~ AUTHORISI (first ..• ,.,.., rrriddlt initial, lost nant)

James A. Whalen

I. REPORT DATE 70. TOTAL NO. OF PAGES 171:\ NO. OF REFS

27 July 1970 30 17 .... CONTRACT OR GRANT NO • '"' ORIGINATOR'S REPORT NUMBE,_-5)

AFCRL-70-042~ b. PROJECT, TASK, WORK UNIT NOS. 5631-14-01

c. DOD ELEMENT 61102F tb. OT~ERfJ.PORT N'fSI (Anyothtrnumbtt! thai may bt ouosne ,. report J.:: H p N

0. 3 27

d. DOD SUB ELEMENT 681310

10. !>ISTRI'3UTION STATEMENT

1-This document has bee n approved for public releaf;e and sal e ; its distribution is unlimited.

II. SUPPLEMENTARY NOTES 12. SPONSORING MILITARY ACTIVITY

Air Force Cambridge He s ear·ch Labora to r ies (CRP)

TECH, OTHER L.G . Hanscom F ield Bedford, Massachusetts 01730

13, ABSTRACT

A nomogra phic compute r is presented which graphica lly conve rts geographical coordinates and universal time into geomagnetic coordinate s a nd geomag ne tic local time in the CoM'ected Geomagnetic syste m of Hultqvis,t. The computer is formu-lated as a map of high latitude s in the Northern He misphe r e on which th e position of the auroral oval can be projected direc tly for any time of day, for any magne tic activity, with account being take n of seasonal variation of the geomagne tic l ocal time coordinate . Instructions for its use , discussion of its accuracy, and examples of its application are given.

DD 1 !~:"as 1473 Unclass ified

S•curi1y Classifica1ion

Sec:urily Cluai&c:uion

, .. IIlEY WO"OI

LINK A LINK a LINK C

"OLIE WT "OLIE WT "OLE WT

Auroral Oval

Nomogr a ph

Geo magne tic Coordinates

Geomagne tic Lot:al Time

Arctic Ionos phe r e

Airborne R e s earch

Unclassified Sec:urily Clulli fi cation