UNIVERSAL ASPECTS OF ATMOSPHERIC HLECTRICITY 
ometers during normal weather but, in the vicinity of 
storms, effects which may be attibuted to these factors 
(particularly the last two) were observed by O. H. Gish 
and G. R. Wait at considerably higher altitudes. 
The rate of ion formation g, when cosmic radiation is 
the only ionizing agent, depends on factors (1) and (2). 
Values for ¢ as a function of altitude are shown in Fig. 1. 
These computed values are based on observations of 
cosmic radiation reported by Bowen, Millikan, and 
Neher and on average data for temperature and pres- 
sure for each of the two latitudes. The value of g in- 
creases from a low value at sea level to a maximum at 
an altitude of 12 to 13 km. The maximum for the higher 
latitude is more than two times that for the lower lati- 
tude. 
OMAHA, U.S.A. 
(MAGNETIC LATITUDE 5I°N) 
| 
MADRAS, INDIA 
(MAGNETIC LATITUDE 
1 
I 
ALTITUDE ABOVE SEA LEVEL (KM) 
fo) 10 20 30 40 50 
RATE OF ION FORMATION (ION-PAIRS CM °SEC'!) 
Fic. 1—Rate of ion formation by cosmic radiation for 
tea low latitudes. (From data of Bowen, Willikan, and 
eher. 
An increase of conductivity with altitude was first 
shown. by measurements of \ made on twelve balloon 
flights during the period 1905-20. Eleven of these 
started in Germany and one in Russia. The maximum 
altitude at which measurements were made was less 
than 6 km except for one in which it was nearly 9 km. 
Continuous registration of \ up to a maximum alti- 
tude of 22 km was made during the flight of the strato- 
sphere balloon Haplorer IJ [14]. The results for this 
flight are shown in Fig. 2. The crosses on graph A 
represent direct measurements of \,, and the circles 
represent values derived from direct measurements of 
A» by multiplying the latter by 0.78. This factor is the 
ratio of the mobility of positive ions to the mobility of 
negative ions. The smooth graph B represents values 
105 
calculated from measured values of cosmic radiation and 
of temperature and pressure, the latter two observed 
during the flight. During this flight the conductivity in-' 
creased from the surface up to an altitude of 18 km 
(60,000 ft) where it was about 100 times the value at the 
surface. In the altitude range 18-22 km, it varied ir- 
regularly but in general decreased with altitude. This 
70 
L 
- 60 
iva} 
WW 
te i 
Ww 
(S) 
0 50 
(a) 
= _ 
a [ S 
=) x 
2 Ss 
= 40 a) 
ce _ 
=} W 
ita} =) 
ci 
WW qt 
=) \ wu 
30b ! 
qt i 
<i y LEGEND | w 
® ii A—POSITIVE CONDUCTIVITY FROM 5 
w [ ‘ REGISTRATIONS DURING DESCENT., | @ 
3 26 f B- POSITIVE CONDUCTIVITY CALCU- w 
a =u LATED FROM OBSERVATIONS OF 3 
w ne COSMIC RADIATIONS, ASSUMING Jo FE 
a Ex THAT SMALL IONS ALONE ARE E 
= yi INVOLVED. a 
= 10 i| | | 
< 1 
x 4 
x 
i \ n ieee oO 
0) 
20 40 60 80 100 
XIN UNITS OF 10°* ESU 
Fic. 2.—Air conductivity, flight of Hxplorer IJ near Rapid 
City, South Dakota, November 11, 1935. 
last feature may be attributed to the presence there of 
substances (perhaps Aitken nuclei) which served for the 
formation of large ions. This decrease of conductivity 
is in the same region where ozone was simultaneously 
found to be especially abundant. Whether this feature 
is universal, whether it is generally associated with 
ozone, and whether there are factors in the atmosphere 
at yet higher levels which effect a similar diminution 
of the conductivity are questions which have important 
bearing on other than electrical aspects of the atmos- 
phere. Therefore, further investigation of the con- 
ductivity of the high atmosphere is called for. At 
present, there is indirect evidence which indicates that 
this diminution of conductivity at high levels is either 
not universal or else is rather limited in vertical extent. 
The unexplored region to which this statement applies 
extends from 22- to about 60-km altitude. Above 60 
km the concentration of ions has been determined at a 
number of places on the earth by quantitative studies 
of the “reflections” of radio waves. Such observations 
demonstrate that the air above that level is extraordi- 
narily conductive. 
Other measurements of \ up to an altitude of over 14 
