We thank Nienteecomesembra for the signal.
Artificial strontium and barium clouds in the upper atmosphere purchase $ 31.50
H. Föppla, G. Haerendela, L. Hasera, J. Loidla, P. Lütjensa, R. Lüsta, F. Melznera, B. Meyera, H. Neussa and E. Riegera
Max-Planck-Institut für Physik und Astrophysik, Institut für extraterrestrische Physik, Garching bei München, Germany
Received 24 September 1966. Available online 21 October 2002.
Experiments with strontium and barium vapour releases in the upper atmosphere, carried out in the Sahara and in Sardinia in 1964, are discussed. The yield of evaporated metal was tested for different chemical reactions. Sr proved to have efficiencies up to 40 per cent. For Ba a mixture of CuO and Ba gave the best results with a yield of nearly 7 per cent. No Sr ions were observed in the experiments. Barium, however, is strongly ionized. The ionization proceeds in two different steps: during the initial phase with a characteristic time of about 5 sec and by a slower photoionization process with a characteristic time of about 100 sec. The diameter of the neutral clouds increased as one would expect for purely molecular diffusion. The rate of increase in the central intensity of the clouds at sunrise was greater than the rate of decrease at sunset. Atmospheric wind velocities of 50-130 msec−1 were determined from the motion of the neutral clouds. The motion of the ion clouds perpendicular to the Earth’s magnetic field in- dicated the presence of electric fields. The initial expansion velocity for explosive mixtures was greater by about a factor of four than the mean thermal velocity of the atoms at a temperature of about 3000°K.