A diurnal study of the electrical structure of the equatorial middle atmosphere

A diurnal study of the electrical structure of the equatorial middle atmusphere C. Communications

and

Space

L. CKOSEKS.L. c’. HALE.

J. D. MITCHELL.

D.

MOCHA

Sciences Laboratory. Department of Electrical Engineering. Universlt~.~~niversity Park. PA 16801. U.S.A.

The

Pennsylvania

State

and

Laboratory

for Extraterrestrial Physics. National Aeronautics and Space Administration. Goddard Space Flight Center. Greenbelt, MD 20771. U.S.A.

Abstract-Electrical parameters measured from I iS km down to below 20 km during the Project Condor campaign at the Punta Lobos Rocker Range near Lima. Peru. are presented Ten rocker-launched payloads measured electrical conductiv!t!. A strong diurnal influence due to solar ultraviolet radiation is shown. Nine of the payloads also measured electric fields. No large mesospheric vertical electric Fields are found in the data. A calculation of the d.c. global conduction current density at 18 km is smaller than previously measured at low latitudes and does not show the conventional diurnal variation.

1. INTROOtKT10?c

During the Project Condor rocket campaign conducted at the Punta Lobos Range near Lima, Peru (lZ.YS, 76.8”W). a diurnal study of middle-atmosphere electrical parameters was performed using rockets launched between 1635 UT (1 I35 local time) on 8 March 1983 and 1300 UT (0800 LT) on 9 March 1983. Ten rocket-launched payloads were used to measure mesospheric conductivity, and nine of them also measured electric fields. Eight of the payloads were parachute-borne. enabling measurements to be made into the stratosphere. Six of these eight paytoads were Iaunched by Super Arcas rockets. *Present address: 01731. U.S.,\.

I\FGL

PHG,

I-l;mscnm

-\FB.

.\lA

Each had a vertical lanyard and four deployable booms for measurements of electric fields and a Gerdien condenser for measurements of conductivities, ion mobilities and ion densities. The other two parachute-borne payloads, launched by Nike Orion rockets, had the same sensors as the Super Arcas payloads. In addition, these two paxloads aiso had X-ray and Geiger detectors to measure energetic particle flux densities. The remaining two payloads in this series were free-falling. They wsre launched by Nike Orion rockets to higher altitudes and used a small ‘patch’ probe to measure conductivities. Deployable booms on one of these latter two payloads measured night-time electric fietds. A summary of the launch parameters for the payloads of this series is shown in Table 1.

Table 1. Launch paramercrs ior Punta Lohos Range. Peru (12’s. Payload no.

.__~~~ 1 2 3 4 5 6 7 x 9

1r1

Fhght

.-......._ S 8 S 8 9 9 9 9 9 9

March March March March March March March March March March

~~ 19X3 1987 i9S7 19X.3 t9S.: 1983 1943 19X.7 19x3 19X.3

LLfuIlctl rime i l:Ti

Rocket N i ke Oriotl Super Arcaz Super Arcas Super Arcas Super Amis Nike Oriori Nike Ortoll Nikc Orion Super Arcas Super Arcas

Rocket Ilight no.

77’W)

Apogee (km) 113 76 i2 Yi 69 111 89 s9 79 7-t

c. L. CK0SKt.VCl Cr/

836 2. INSTRUMENTATION

The two high altitude free-falling payloads were designed to measure both the electrical conductivity and the three-dImensiona components of the electric held IMAWARD YI al., 1981). This free-falling payload was spin-plane stabilized by two short booms. Six larger. I m fiberglass booms were terminated with 8.$9 cm spherical collectors. High input impedance (greater than IO’” Q) preamps measured the potential of each collector with respect to the 30.5 cm spherical central body of the payload. Various differential combinations of the collector potentials were then telemetered to ground. A small ‘patch’ probe was included on the downward surface of the central body to measure electrical conductivity by observing the V-I characteristic. A Imear sweep of - 5 to f 5 V was applied to the collector and guard electrodes. and the resulting current measured. This probe technique is similar to that of the blunt probe which has been used for many years (HALE er al., 1968). The SIX Super Arczs payloads (Fig. I) used a Gerdien condenser for measurement of the conductivity by observing the V-I characteristic (MITCHELL er al., 1983). The applied collection voltage ranged from about - 25 to + 19.5 V on a high voltage sweep. which alternated with a low voltage sweep of about --4 5 to +3.6 V. The Gerdien condenser also measured ion mobilities and ion densities, which are presented in a companion paper (MITCHELL el trl., 1985). Figure 1 also shows four short booms with exposed IO cm whips at the ends. The potential at each electrode was measured with a high impedance (> lOI Q) amplifier. The supporting electronics telemetered the raw electrode voltages. as well as various differential combinations of the boom electrode voltages. For the test payload shown in the figure, the booms were arranged in two orthogonal pairs with a net electrode spacing of 50 cm horizontally and FO cm vertically between the planes of the elcztrodes The only difference between the test payload (shown 111Fig. I) and the Super Arcas payloads flown as part of Project Condor was that for the Project Condor payloads all four booms deployed radially in the same horizontal plane. Also. each pair of booms was a different length. to enable observation of centralbody wake effects. The net horizontal difference between the sensor centroids was 40 cm for one pair and 30 cm for the other pair. Also shown in the figure is the end of the vertical E-field ‘lanyard’ sensor, This electrode consisted of an exposed metal braid of the same length as the length of the main payload. The nylon lanyard which attached to the parachute was

threaded through the center of the braid. Another high impedance amplifier measured the potential of the exposed braid with respect to the main payload body (HALE e: ol., 1979. I9Sl). The two Nike Orion parachute-borne payloads also used a Gerdien condenser to measure conductivities, mobilities and densities. Long booms with 20 cm exposed whips iverc al-ranged in arthogonal pairs to produce b+,th horirontal and vertical differential (‘boom-dir) voltage measurements. The net vertical displacement of the measurement planes was I m; the net horizontal displacement of the measurement planes was 2 m. A vertical ‘lanyard’ potential measurement was implemented by an exposed metallic braid stretched over the lanyard attached to the parachute. X-ray and Geiger detectors (GOLDBERG et al.. 1981) were used to monitor background radiation levels and the energy deposition produced by the X-ray stellar source. Sco X-I.

3. ELECTRICAI.COI;DLCTf\IT\ The measured conducttvities from the two high altitude flights are shown in FIN. ?(a). The positive conductivities in the mesosphers should be accurate representations of those of the medium. however. the negative conductivities and higher altitude measurements are less accurate. but should still be good relative to each other. (See YORK rt al.. 1982, for a discussion of negative conductivit! accuracy.) Of interest is the wave-like structure in the data above S9 km. which may be related to long wavelength irregularities seen in receat electrojst studies (PFAFF et al.. 1982). However. :he mos! srrlklng feature is the large (two orders of magnitude) drop in negative conductivity at X9 km. The positive conduct;\ ities !‘rom the sight parachute-borne Gerdien ca~?dtnse:r n?~aSurements are shown in Fig. 2(b). .As tii< iisarc, shows. the stratospheric conductlvit! deLlales Irtrle irom ;+1: exponential form escept for the midda! i?i and late nighi (S and 9) measurements. ,+,b~\s 55 km the effects of solar ultravioter penetrdtlons are much more evident. The midday f?~ enhancement is apparent. as well as a rapid dro? In conductivlt\ between sunset (4~ and evening (51 rnsasurzments A; eariier sunrise series (Miictit.Lr <‘I,I/ :9)--l has :ilso observed such strong solar zffscts. The subsequent recovery i7) indicates some undsr+,cct i n the response due to the change iii sold]- II .. probabt:, Lyman-z ioi:izing NO. at SUIIW.

Electrical

SUPER

ARCAS

GERDIEN

837

strt~cture of the middle atmosphere

CONDENSER

PAYLOAD VERTICAL LANYARD/ E-FIELD PROBE

SUPPORTING ELECTRONICS/ BATTERIES CIRCULAR ANTENNA

SLOT

INSULATING SPACER/ ELECTROMETER HOUSING E-FIELD

PROBE

(I

GERDIEN CONDENSER ELECTRODES: L

GUARD RETURN COLLECTOR (NOT SHOWN)

Fig. I. Super Arcas Gerdlen

condenser payload

OF 4)

Electrical

839

structure of the middle atmosphere

120

I IO

100

“CONDOR”

PERU

8 MARCH 8 MARCH

I983 1983

I I35 2206

LST LST

cD UN

I-

/-

I-

7c )-

6C I--

5C )-

IC

CONDUCTIVITY Fig. 2(a). Conductivities

(S/m)

from high altitude payloads !I 076 (d:ny)cind :I 027 (night)

80-

70-

60-z r g x IF 2

9.5.4.10.8

50-

“CONDOR” 8-9 MARCH I983 PUNTA LOBOS RANGE. PERU

s7.3.2

NO ROCKET EST 2 15216 1216 3 15223 1700 4 IS.221 1827

40-

5 7 0 9

15 220 31.032 31.033 15.219

2000 2227 0357 0511

0100 0327 0057 1011

IO

15 222

0700

I200

20 POSITIVE

I o-g

1 0’0

IO”

I o-‘2

CONDUCTIVITY

Fig. 2(b). Positive conductivitlrs

UT I’:6 2200 2327

(S/ml

from eight parachute-borne

payloads

4. EIXCTRIC

FIELDS

The electric field sensors on the high altitude daytime flight did not function properly. On the nighttime high altitude flight at 2206 LT, a downwards mesospheric field of about 0.25 V m-’ was observed, however, this is not considered significant within the limits of error f -0.5 V m- ’ 1.The E-field data from the eight parachute-borne payloads are shown in Figs. 3 and 4. The vertical electrical field data from two independent vertical field sensors on payloads 7 and 8 are shown in Figs. 3(a) and 3(b). Previously at high latitudes, the ‘lanyard’ and ‘boom-dir data have shown good agreement at ali altitudes. Figure 3 shows that the two techniques are in agreement for the fair weather field below 20 km, while between about 20 km and 55 km the ‘lanyard’ shows a large and relatively noisy ‘artifact’ field. Examination of the telemetry record shows jump field changes and recoveries stmilar to those of lightning fields. The individual boom data which was telemetered to ground shows no central body charging effect that could explain the lanyard artifact. It is concluded

that the artifact is probably due to rectification of fast transient lightning waveforms from lightning (present on the night in question in the coastat mountains of Peru and Ecuador) which were picked up by the longer ‘lanyard’. The horizontal magnetic field may prevent a simple direct return of the transient currents to the ionsphere and global circuit. This spreading of the return currents would increase the radius over which such transients would be observed. The electric fields measured on the six smaller Super Arcas payloads are shown in Figs. 4(a), 4(b) and 4(c). On these payloads only the ‘Ian!-ard’ sensor provided vertical field data. The possible lightninginduced ‘artifact’ is present to some degree on all but the midday (2) measurement. The spurious data below about 13 km is due to the loss of good plasmaelectrode contact when the conductivity becomes too small. ‘Large mesospheric fields’ are not evident in any of the measurements. except possibly flight 3 at 1700 LT [Fig. 4(a)]. An errant trajectory of the rocket caused this payload to deploy with a large

“CONDOR” PERU 8 MAR I983 2227 ES-i

90

+

85

3 ,

I .

LANYARD

“CM&R” 8MAR 2227

1983 EST

70

“L

/

E=7

SATURATION LEVEL Of

3.

60

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i

r

3M=D

1

I *

50

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-..

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0

,

DOWNWARD

z

3

E, V/M.

4

5

6

7

B

-2

0

iI ,

DOWNWARD

“LANYARD”

Fig. 3(a). Vertical

11 -I

etectric field on payload

2

3

E. V/M,

31.032 by two methods.

1

II

4

5

“BOOM

11 6

DIF”

7

a

Electrical

structure of the middie atmosphere

841

“CC$gu”R”

“CONDOR” PERU 9 MAR I983 0357 EST

80 LANYARD

3 I ,

-

9 MAR 0357

1983

EST

“L

60

..

SATURATION LEVEL OF ELECTRONICS

..3

.

‘I50

. f..

+

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d :

D

;

r

3M=D

“L-VP

:

60

D=3 50

:I

:.

.. 40

c

. 30

+

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;. . :-

PAYLOAD

40

-

30

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.

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+

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I

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3

4

E, VIM.

5

I

I

I

II

6

7

8

2

velocity at a low altitude. The apparent electric field peak at 50 km may be an artifact. The ‘common mode’ voltage sensed on the individual booms on this payload indicated the ‘Come11 artifact’ (KELLEY et al., 1983) in that the voltage was larger in magnitude on the shorter pair of booms (30 cm horizontal displacement), which are in more of the payload wake.

5.

CONDtXTiON

:

pdybxld

3 1.0!3

._ ‘I

11

11 0

-/

I

DOWNWARD

“LANYARD”

Fig. 3(h). Vertical electric field on

.’

+

10

. .

hq two

2

D= I . .

11 3

E, V/M,

4

“BOOM

11 5

6

J 7

8

DIF”

methods

A decrease in conductivity caused the decrease below 1 pA me2 at 0357 LT (8). while an increase in the electric field at 051 t LT (9) produced a current over 7 pA m- ‘. The values are generally much smaller than we have observed previously in Kenya (t6 February 1980) and at higher latitudes. The diurnal variation did not, in this series of measurements. reflect the Carnegie’ diurnal variation. which is a variation in unl\ersal time with ;I maximum near IX00 t_T

CL RRFNT

The conductivity data (a) and the electric field data (E) from the parachute-borne payloads have been combined to yield the vertical ‘fair weather’ conduction current density (J) shown in Fig. 5. Conductivity profiles for payloads 7 and 8 are shown in a companion paper (GOLDBERG et a/., 1985). An altitude of 18 km. where the combined E-field and conductivity data were most complete, has been used. The figure shows that the current was relatively steady, except for the two late-night Rights (8 and 9).

A diurnal series of rocket-borne payloads has yielded conductivity data and electric field data over the 115-20 km region. The conductivit~es above 55 km show a strong solar ultraviolet dependence. as expected. Wave-like structure is seen in the data in the E-region. At sunset there is an apparent conductivity undershoot in the mesosphere, which recovers later in the night. The vertical etectric held data show several types of artifacts. but no apparent ‘large field’. A calculation of the global dc. current density

c.

842 3”

+

80

+

70

2:. 2. .. 4;‘ .. :_,

L.

CROSKEY PI a/.

“CONDOR” PERU 8 MAR 1983 1216 EST

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3

4

5

6

7

8

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“LANYARD” Fig.

90

30

E.+p

\

DOWNWARD

4(a). Vertical

electric

fields for pa\loads,I

t

.:y

80

“CONDOR” PERU 8 MAR 1983 I827 EST

1’ ‘; :.i \

70

5;

90

+

80

+

70

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3

E. V/M,

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4

5

6

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15.22:

“CONDOR” PERU 8 MAR I983 2000 EST

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6

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“LANYARD” Fig. 4(b). Vertical

11 -2

‘;

+

-I

11 0

I

DOWNWARD electric

fields for pa!loads

I 2

II 3

E. V/M.

IS.ZZIand

4

1 5

“LANYARD”

15.270

Efectrical

90

+

80

+

structure

of the middle

90

c

80

+

“CONDOR” PERU 9MAR 1983 051 I EST

843

atmosphere

“CONDOR” PERU 9 MAR 1983 0700 EST

70

60

60

50

50

+

40

40

+

30

30

+

20

20

+

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2

3

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“LANYARD”

Fig. 4(c). Vertical

electrtc

fields for payloads

“CONDOR” 8-9 E,cr,

E. V/M.

IS.?19 and

5

f

f

I

6

7

a

“LANYARD”

I5.1?2

PERU

MARCH, J AT

I983 18

km

6 4

,,I

I,,

*

is-r

12

t6

20

US

17

21

I

Fig. 5. Electric

field. conductivity

I

0 5 and conduction

t

4 9 currents

I

ISI4 8 i3

at IS km.

844

C. L. CROSKEY et (11.

observed at 18 km produces small values which not follow

the ‘Carnegie’

universal

time

payloads and rocket launches

do

variation

(ISRAEL. 1973).

Comision spatial.

Ackrloa,ledye,,tp,cts-- -We gratefully tance of the personnel of Wallops

acknowledge the ass,sFlight Facility with the

Launch

support at the Punra

Lobos Range, Peru. was also provided by the Institute Geofisico del Peru (Dr R. WOODMAN. Director) and the

National This work

nautics and Space NAG 6-7).

de Investigation

y Desarrollo

was sponsored

by the Kational

admlnistrdtion

(grants

AeroAero-

NsG-600-l

arid

REFERFJVCFS GOLDBERG R. A.. JACKMAU C. H.

and BARCUSJ. R. GOLDBERG R. A.. BARCVS J. R. and MITCHELL J. D. HALE L. C. and CROSKEI. C. L. HALE L. C.. HOULT D. P. and BAKER D. C. HALE L. C.. CROSKEYC. L. and MITCHELL. J. D. ISRAELH. KELLEY M. C.. %EFKlVG C. L. and PF.~FF R. F. JR MAYNARD I\I. C.. CROSKEY C. L.. MITCHELL J. D. and HALE L. C. MITCHELL J. D., SAGAR R. S. and Orsr:

1984 198s 1979 I968

Nature 278, 2S9. Space resseorch 1111. p. 320. North-Holland

1981

Geophys. Res. Lett. 8.927

1973 1983

Geophys. Res. Letr.

1981

Geophys. Res. Len. 8. 923

1977

1983

RYCROFT M. J. and ST~CKLANDA. C Eds. p. l9Y. Pergamon Ox ford. J. armos. terr. Phys. 45, 5 I5

I985

J. ut~)ws. ICI’I‘. P/IIX. 511hmlrtrd

19e2

Geopllys. Res. L~rr. 9. 688.

I982

J. atmos. terr. Pltys. 44. 251

R. 0.

MITCHELL J. D.. HALE L. C., CROSKE~ C. L. and OLSEN R. 0. MITCHELL J D.. FUCNTESJ. R.

J. geophys. Res. 89

Atmsphrric

Kcter Press. Jerusalenl IO, 733

E/,vrricir~..

Space Research X C’II,

and CROSKCVC. L.

PFAFF R. F.. KELLEY M. C.. FUER B G.. MAYNARD N. C. and BAI;FR K. D. YORK T. I\f. OLSEY R. 0.. MITCHELL J. D. and MOTT D. L

Amsterdam

Press.

!ilr !>u[>llc~t,~,>