ASTRONOMY AND ARTIFICIAL SATELLITES—GOLDBERG 295 
prehend the physical nature of flares and to understand the causes of 
disturbances to the earth’s atmosphere, it is necessary to observe 
directly the ultraviolet radiation that is now screened from observa- 
tion on the ground by the earth’s atmosphere. The ultraviolet radia- 
tion responsible for ionospheric disturbances has, as a result of rocket 
investigations, been narrowed to a choice between the so-called Lyman- 
a line of hydrogen, which falls at 1216 A., and soft X-rays of wave- 
length between 5 and 10 A., although the most recent evidence favors 
the X-rays. 
To resolve the question as to whether the Lyman-a radiation 1s 
directly responsible for sudden ionospheric disturbances, it would 
be sufficient to monitor continuously the total flux of the radiation 
from the whole solar disk that strikes the top of the earth’s at- 
mosphere. Observations of this type have been made during short- 
time intervals from rockets, but continuous surveillance for extended 
periods from satellites is an absolute necessity. However, such ob- 
servations can yield little information concerning the origin and basic 
physics of the flare phenomenon and its interactions with other related 
solar activity. The integrated flux observations are also not suitable 
as a basis for the refined prediction of sudden ionospheric disturb- 
ances. For these broader purposes we require monochromatic photo- 
eraphs of the sun in the radiation of Lyman-e, similar to and con- 
current with those now being obtained in the red Ha line from the 
ground. The first detailed photograph of this type was obtained by 
Tousey and associates at the Naval Research Laboratory from an 
Aerobee rocket on March 13, 1959 (see pl. 4). 
Eventually, simultaneous photographs should also be obtained in 
the ultraviolet lines of other elements in addition to Lyman-a of neu- 
tral hydrogen. The most significant lines for this purpose would 
be those of He I at 584 A. and of He II at 304 A. An interesting 
byproduct of this program would be the light it would cast upon 
the detailed structure of the chromosphere, a subject about which 
there is considerable controversy at present. Thus, there is much 
evidence that the chromosphere is not homogeneous and that it con- 
sists of heterogeneous hot and cold columns with widely differing 
temperatures ranging from perhaps 5,000° to 50,000°. The high- 
excitation helium lines seem to be produced in the hot regions, 
whereas the radiation in low excitation lines defines the cool regions. 
Comparison of monochromatic photographs made in the different 
lines might reveal the detailed character of the temperature 
fluctuations. 
A most valuable byproduct of the solar observations would be the 
detailed information they could provide on the earth’s upper atmos- 
phere. About 12 years ago, and even prior to the first successful 
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