SECRETARY’S REPORT Q7 
time, rapidly converging procedures for calculating the structure of 
model atmospheres for hot stars, with given chemical composition, 
effective temperature, and surface gravity. He has formulated a 
method for calculating the structure of shock fronts in completely 
ionized hydrogen and in the presence of magnetic fields. The 
calculations contribute to our understanding of the fundamental 
properties of ionized gases. Procedures were devised for translating 
a microscopically formulated problem of gas dynamics into an ap- 
proximately equivalent continuum problem. This method applies par- 
ticularly to cases in which the Knudsen number, X, is not very small. 
Dr. Krook continues to study various problems in the dynamics of 
gases and the kinetic theory of gases. 
Dr. Charles A. Whitney has begun a study of atmospheric structure 
and its correlation with solar activity. This work involves empirical 
analyses of satellite and solar data as they relate to atmospheric 
physics. Dr. Whitney continued his study of gas dynamics in astro- 
physical contexts, to obtain a numerical solution of the nonadiabatic 
equations of motion for the solar atmosphere. The procedure involves 
integration of the equations of motion for a variety of conditions. 
This is the first critical investigation of the propagation of nonlinear 
and nonadiabatic waves in the solar atmosphere. It will provide a 
basis for the interpretation of high-resolution photographs of the 
solar disk obtained by balloon-mounted telescopes. A comparison 
between the adiabatic and nonadiabatic equations will have a direct 
bearing on the theory of stellar chromospheres. A program to pro- 
vide a firm basis for the theory of stellar pulsation was initiated by 
Dr. Whitney in 1955. This fundamental problem of classical astro- 
physics requires a variety of procedures, primarily theoretical. With 
the help of Dr. John Cox, the development of machine methods for 
the solution of pertinent equations has made considerable progress. 
Upper atmosphere.—Dr. Jacchia’s research on the secular accelera- 
tion of artificial satellites enabled him to establish marked transient 
effects on the acceleration of Satellite 1958 Delta One, which coincided 
with the great magnetic storms of July and September 1958. Dr. 
Jacchia’s study established that these variations in acceleration were 
not due to solar electromagnetic radiation but to solar corpuscular 
radiation. ‘This novel result is of outstanding significance in the field 
of solar-terrestrial relationships. 
Studying the orbital accelerations of Satellites 1958 Beta Two and 
1958 Delta Two, Dr. Jacchia found that they show semiregular fluctua- 
tions with an average period of 29 days. Further study suggested 
that a semiperiodic variation in the solar radiation with the synodic 
period of rotation of the sun, 27 days, seemed a more probable cycle. 
Dr. Theodore E. Sterne completed a study of the inferential 
