Various attempts had been made over the years to correlate magnetic storms with various terrestrial phenomena, and it was to this task that many IGY personnel devoted themselves. A few years ago, a Harvard meteorologist, the late H.H. Clayton, tried to establish a connection between earthly weather and solar activity. It appeared that during peaks of sunspot activity there tended to be more icebergs in northern latitudes, while in the Temperate Zone temperatures were subnormal and precipitation abnormal. It might be pointed out that during the great magnetic storm of February 10 the eastern and central parts of the United States were suffering from the worst cold waves of the winter.
Astronomers tend to ignore such seemingly unscientific efforts, but there is some degree of evidence that the sunspot cycle is connected with all sorts of things. Measurements of the growth rings of Arizona trees reveal that they grew faster during sunspot peaks, and such things as Canadian rabbits, Atlantic salmon and meningitis cases in the United States have all been found to go through cycles roughly equal in length to the sunspot cycle. Even in the stock market has been connected with sunspots. High and lows for both occurred in 1928, 1933, 1937, 1946, and 1958, but to say the least, it would be hard to prove any connection between them.
The most startling new connection between solar activity and terrestrial phenomena was made by men not officially under IGY organization, but working closely with IGY personnel at the Smithsonian. It was typical of a number of important finds; for many of IGY's most distinguished and valuable contributions have come from scientists not working under the Geophysical Year grants from the National Science Foundation. The whole concept of setting aside a year or eighteen months for special cooperation in the sundry fields of science was so broad a project that it touched people whose whole lives have been dedicated to research in specific areas--oceanography, meteor study, or sunspot work, for example.
Many of these individuals were singled out of IGY grants. Some of them shifted the emphasis of their work, or moved into allied fields; others continued working in their specialties, cooperating with foreign scientists in the same project. But the large majority were not singled out to work under the auspices of the IGY funds voted by Congress. To create a distinction between IGY scientists and non-IGY scientists would, of course, be artificial for on most projects the source of the funds was merely an idle afterthought. In fact, the basic contribution to the satellite program--the on-the-spot recording of data--was made by thousands of unpaid amateurs organized into "Moonwatch" teams.
What has proven to be one of the most important single discoveries in all of the IGY work was formulated chiefly by a man not directly associated with IGY, but working closely with IGY personnel in Cambridge, and a German working in the same field. The discovery--a startling correlation between the movements of five earth satellites and radio wave emission of the sun--is the most marked relation between solar and terrestrial phenomena ever found. The man behind this important find is a good-natured, gray-haired man named Luigi G. Jacchia. A meteor expert by trade, Jacchia may be found more often than not hunched over a drawing board plotting graphs in a small corner office at the Smithsonian Astrophysical Observatory building on Garden St. Fittingly, it was his drafting work which led to his discovery of the correspondence of the two phenomena, by noting that the peaks and through of the two plots coincided.
"I was basking in the sun of my native Italy when the first satellite went up," Jacchia recalled. "I came back ten days after Sputnik I was launched. Everything was in a state of confusion. People were sleeping in my former offices. There was such general despair on people's faces that I decided to help." With his proficiency in upper atmosphere dynamics from his work on meteors, his help was not insignificant.
The first problem that had to be met was the inability of the computer programs to keep up with the satellite in calculating the orbit. Preliminary plans expected the satellite to be higher up than it was and so did not account for the rapid changes in the orbit's elements, caused by its encounter with the earth's atmosphere. These variations in velocity nearly drove the mathematicians crazy, for they showed no apparent regularity. Now it is know that if a satellite encounters atmosphere its angular momentum is decreased, and this produces a decrease altitude and a decrease in period. At first it was thought that the variations were due to the differing area presented by the satellite as it turned over and over in orbit. Jacchia wrote in the Smithsonian's "Special Report No. 9," issued February 21, 1958:
"An interesting feature...is the erratic fluctuation in the orbital acceleration. A simple explanation of these changes may lie in a systematic variation of the effective presentation area of the satellite, although variations in the density of the upper atmosphere cannot be dicounted as a possible cause."
The latter eventuality, added almost as an afterthought, turned out to be the critical factor. During the summer it was determined in that spherical satellites also behaved in the same peculiar fashion as the cylindrical satellites. By late September Jacchia had discovered some periodicity in the acceleration of Sputnik II and ruled out change in presentation area of the satellite as a factor. He wrote:
"It appears that the acceleration varies rhythmically, with cycles of duration of 24 to 37 days...Of particular interest is the sharp rise in the acceleration in the second half of August, when it increased by a factor of 4 in just over two weeks.
"The fluctuations in 1958 Beta Two ... seem to suggest ... semi-regular changes in the atmospheric density such as could be caused by variable solar radiation--for which one would expect to find occasional periodicities of the order of 27 days and possibly a correlation with geomagnetic activity."
Evidence which would seem to back up this theory was that the 27-day period of rotation of the sun (with its spots and flares thought to emit charged particles) corresponded roughly with the periods indicated by the satellites, and that the sharp increase in acceleration at the end of August was also two weeks of strong geomagnetic activity. The problem that remained was to find some traceable phenomenon of the sun that could be compared with the daily fluctuations in the acceleration of the satellites (by this time all five satellites showed the same acceleration characteristics, which occurred simultaneously).
At first Jacchia sought some connection between solar flares and the acceleration of the satellites. When the flares proved too erratic he turned to geomagnetic data. Again the correlation was poor.
The big break-through came when Dr. Priester of the Bonn Observatory called Jacchia's attention to the connection between solar radio wave data and the satellites' acceration. The very first hint Jacchia saw was that two peaks in an otherwise calm period occurred at the same time on both the satellite graph and the graph of 20 cm. solar radiation. With observations of 10.7 cm radiation transmitted daily from the National Research Council at Ottawa, Canada, he took a longer look, and found the amazing correspondence between solar emission and satellite acceleration reproduced above. This one-for-one relationship led him to form in December the daring conclusion that some sort of particle emission, or wave emission, from the Sun was responsible for the variations of the satellites. This would mean, he said, that the density of the upper reaches of the atmosphere was increased during periods of high solar activity. Not only had it been thought that the upper atmosphere was ten times less dense than the satellites proved it to be, but it was never suspected that the density varied with radiation. An IGY publication pointed out that these discoveries "will have a farreaching effect on interplanetary travel." They certainly will be important to the new X-15 rocket plane, projected to fly 400 miles above the Earth's surface.
Unlike many of the IGY projects, the satellite program continued after the end of the Geophysical Year, and grows more complicated daily. It is only now that studies such as Jacchia's are being implemented.
The job of interpreting the six billion calculations made each week by the IBM 704 computer is carried on by a small number of mathematicians and upper-atmosphere specialists at Smithsonian, many of whom also lecture at the University. Fred L. Whipple, Director of the Smithsonian Observatory, is an expert on meteors and meteoric risk to satellites as well as optical tracking; Theodore E. Sterne, Associate