Reference 12 are reproduced here. Figures 17 and 18 show the field
strengths of NSS as measured by DRL at Kirlmewton, Scotland and Thule,
Greenland, respectively. These are essentially north-south paths, with
that to Kirlmewton skirting the auroral zone, and that to Thule penetrating the auroral sone. Figure 19, for the NPM-Thule path, is also
north-south penetrating the auroral zone.
Figures 20 and 21 are plots
of the field strengths of NPM and NSS, as measured by DRL at Austin on
the same days and at the same times. These data are for an east-west
path.
It is readily apparent that there was considerable variation in
recorded field strengths from day-to-day and during the day. Day and
night variations in signal strength are generally more pronounced on
The magnitude of diminution in
24 March 1954
27 April 1954
6 May 1954
1.00
0.90
080 .
0.70
060
>
oO
050
°
FIELD STRENGTH (MILLIVOLTS PER METER)
the north-south path than east-west.
oO
°
uw
Sunrise at midpoint
4-F
mann
}
1
t
°
fo)
fo}
°
iy
+
0000
0500
1000
1500
2000
2400
GREENWICH MEAN TIME
Figure 17 Plot of the field strength of NSS as measured by
DRL at Kirknewton, Scotland.
signal from dark-to-daylight paths was apparently greater when the
auroral zone was penetrated. At Thule and Austin field strengths were
lower during magnetically dieturbed periods (i.e. 24 March 1954) than
during relatively quiet magnetic periods (4.0. 6 May 1954). Magnetic
factors from the Cheltenham Magnetic Observatory were used as criteria.
The average daytime field strength from NSS at Kirknewton (5,800
km) was about 0.45 mv/m, while at Thule (4,000 km), it was about 0.03
mv/m. If equal attenuation per 1,000 km is assumed for both paths,
then NSS-Thule is low by 25 to 30 db as compared with NSS-Kirknewton.
The NPM-Austin path on 24 March, 27 April and 6 May 1954 showed
higher day and night field strengths during magnetically disturbed
periods than when comparatively quiet. This is an apparent disagreement with the NSS-Thule and NSS~Kirknewton results; however, it is in
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