160 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 64 



high latitudes.^ Atmospheric density variations, which directly in- 

 fluence satellite drag, are interpreted as the result of temperature 

 changes in the atmosphere. Dr. Luigi G. Jacchia generated a com- 

 prehensive model of the major temperature variations — diurnal, with 

 solar activity, with geomagnetic activity and semiannual — for presen- 

 tation at the fifth International Space Science Symposium in Florence 

 in May. Dr. Jacchia and Jack W. Slowey found that the heating 

 accompanying geomagnetic disturbances was greater in the auroral 

 zones than at middle latitudes; on quiet days, however, there is no 

 detectable latitude effect. The relation between atmospheric heating 

 and the geomagnetic index Ap, which had been found to be nearly 

 linear during magnetic storms, was found to depart very markedly 

 from linearity on near-quiet days. This finding implies greater heat- 

 ing from this source than had been suspected before. 



Plans are being drafted for a construction of quasi-static atmospheric 

 models to be followed by dynamic models to fit the observed density 

 data. 



Techniques other than satellite tracking are also useful in high- 

 atmosphere studies by Observatory scientists. Instrumentation aug- 

 menting the Radio Meteor Project has been developed by Dr. Mario 

 D. Grossi to measure wind velocities at altitudes about 90 km. above 

 ground level by collecting and processing doppler information con- 

 tained in radar returns from meteor trails.* A network of three sta- 

 tions about 50 km. apart will allow at least two determinations per 

 hour of the three components of the wind velocity vector with an 

 accuracy of a few m sec"^. 



Dr. N. P. Carleton conducts a program of research that includes 

 laboratory study of certain atomic collision processes and analysis 

 of phenomena of the aurora and airglow in terms of the collision 

 processes involved.^ In the laboratory Dr. Carleton and Dr. Charles 

 H. Dugan have been continuing study of excitation of metastable 

 states of Na, O2, CO, and O by electron impact, combined with a 

 study of subsequent collision processes involving these metastable 

 atoms and molecules. Dr. Carleton has modified computer programs 

 to examine the solution of two new problems: (1) the exact heating 

 effects of the input of energetic photoelectrons into the ionosphere 

 during the day, with application to the excitation of the dayglow, and 

 (2) the calculation of the heating effects that could be produced in 

 the ionosphere by a rocket-borne transmitter. 



Dr. Carl Sagan and his colleagues considered several phenomena 

 and properties of the pin net Venus. The 8-13 micron limb-darkening 

 observations of Venus from MaHner II nnd other observations have 

 been shown to be consistent with a wide variety of models of the 



See footnotes, p. 177. 



