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FEELY AND BAZAN
monthly basis.
These data are presented in Fig. 8. In August 1961,
before the U.S.S.R. 1961 test series began, the highest activities were
found at 70,000 ft, the highest altitude sampled, In March 1962 high
Sr activities were found in the layer between 55,000 and 65,000 ft. By
July 1962 debris from the high-yield devices tested by the U.S.S.R. in
October 1961 had reached 31°N, and quite high ‘Sr activities were
found in the layer between 60,000 and 70,000 ft. Even at this time,
however, no Significant quantities of U.S.S.R. debris were found in the
stratospheric layer between 80,000 and 105,000 ft.
The best explanation for this observation is that significant quanti-
ties of U.S.S.R. debris had not been injected into this high layer. It
could be postulated that debris was injected into this layer in late 1961
but that subsidence or particle settling brought it down into the lower
Stratosphere by mid-1962. Either or both of these factors may have
affected the debris during the first nine months following its injection,
but neither the data for 65°N (Fig. 7) nor those for 31°N (Fig. 8) show
effects in the lower stratosphere attributable to these factors. It seems
unlikely, therefore, that they played more than a secondary role in the
movement of the debris during the winter of 1961—1962. Sporadically
during early 1962 debris from the high-yield October 1961 events was
found in WU-2 samples collected in the northern polar stratosphere in
the layer between 60,000 and 70,000 ft. When, after April 1962, this
debris reached the Star Dust sampling corridor to stay, it was still in
this same layer. This is consistent with the hypothesis that the failure
of both the WU-2 and the balloon sampling to find it earlier had resulted
from incomplete mixing of the debris in the zonal direction. Apparently
a reasonably uniform zonal distribution of the debris had been achieved
at the higher latitudes by May 1962 and at 31°N by July 1962.
‘Debris from the 1962 U.S.S.R. tests (including the late December
1962 tests’) was found at 31°N in the layer between 60,000 and 70,000ft
during January 1963 (Fig. 8). By December 1963 lower concentrations
were found in this layer, but the concentrations in the layer between
65,000 and 105,000 ft had increased. Concentrations at all altitudes had
decreased by May 1964.
Sampling in the southern hemisphere at 34°S (Fig. 9) revealed
somewhat different vertical distributions of debris, but the similarities
between the distributions at 31°N and 34°S are more striking than the
differences when it is considered that all important injections of debris
into the stratosphere have occurred in the northern hemisphere.
No detectable debris from the 1961 U.S.S.R. tests had reached 34°S
by November 1961, and significant quantities had not reached that latitude by February 1962. By December 1962 debris from Dominic I had
reached 34°S but not in sufficient quantity at most altitudes to raise the
concentrations above those found there in November 1961. At 105,000 ft,
however, most of the Sr present was attributable to the United States