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|International Geophysical Year
IGY was an 18-month period during which scientists of 66 countries conducted an unprecedented study of the earth and its cosmic environs.
In 1950, a group of geophysicists suggested that with all the new scientific tools then available -- rockets, radar, computers, etc. -- it was time for a coordinated, worldwide study of Earth's systems. It was further suggested that such a study be timed to coincide with an expected peak of sunspot activity and several eclipses. The suggestions were presented to the International Council of Scientific Unions, which designated July 1, 1957 through December 31, 1958, as the IGY.
In the seven years leading up to the IGY, a series of assemblies were convened to establish the criteria for the effort and to ensure adequate geographic coverage. Emphasis was placed upon those fields requiring worldwide networks of stations, including meteorology, ionospheric physics, and geomagnetism. The exact content of the program of any specific participating country depended upon its scientific resources, logistics capabilities, and geography. During the planning period, a permanent research station in the Antarctic was built; scientists designed and built precise instruments, as well as rockets and balloons that would carry these instruments into the atmosphere and space; and technology first developed during World War II was adapted for peaceful purposes.
Research and Results
The primary purpose of the IGY was to secure data in all those fields of geophysics which required simultaneous measurements about the Earth. In all of those fields, the planned measurements were made and the data were sent to three World Data Centers, established specifically for the orderly recording and indexing of the millions of results obtained.
One of the chief reasons for selecting the July 1, 1957 through December 31, 1958 period was that it was predicted to coincide with a maximum in the sunspot cycle when solar activity was at its greatest and thus afforded an unusual opportunity for examination of solar events and their impact upon Earth's upper atmosphere. The period did indeed prove to be an active one, and the highest yearly mean in relative sunspot numbers since 1778 (when records were first begun) was attained during the IGY.
A continual watch was kept of the Sun through 100 solar patrols operated by observatories of 33 countries. The principal purpose was to detect the onset of solar flares and to study their terrestrial effects. When a patrol determined that terrestrial effects might occur in the wake of a solar flare, IGY scientists throughout the world were alerted so that measurements could be intensified. One of the early IGY rocket discoveries revealed that X-rays associated with some flares penetrate to the lowest stratus of the ionosphere and increase the ionization appreciably, and that the increased ionization was likely responsible for radio communications blackouts. Rocket firings during the solar eclipse of October 12, 1958, revealed that the X-rays originate in the Sun's corona, for they were still detected while the Sun's disk was shielded by the Moon; in addition, the absence of ultraviolet light indicated that these radiations are not products of coronal activity.
Much new information was also gained about the Sun itself. For example, the solar patrol program included extensive photography of the Sun throughout the 18-month period, with many observatories taking pictures every minute or even more often. These photographs provided the most detailed history of the Sun ever compiled and afforded solar astronomers a unique body of data during the greatest sunspot cycle ever observed.
Cosmic ray experiments conducted aboard ships voyaging to and from the antarctic and on an aircraft expedition around the world revealed that there are significant discrepancies between the description of the magnetic field obtained from classical geomagnetic observations and that obtained in some of these experiments. The latter suggest that the magnetic equator of the Earth for cosmic rays may be rotated more than 40 degrees westward from its generally assumed position. It was also determined that there is an interaction of the geomagnetic field with fields or plasma in the interplanetary medium.
A total of 195 cosmic ray stations were operated during the IGY by scientists of 31 countries. One of the objectives of the program was to examine changes of cosmic radiation with time, and monitors determined that the total intensity of cosmic ray particles above the atmosphere, as of early 1958, had decreased to at least one-half the intensity observed in 1954. Morever, high-altitude balloon flights indicated that the lower energy particles practically disappeared in the intervening years. Intensity changes of short duration but of large magnitude were also observed, usually in the days following a major solar event.
The IGY afforded the first opportunity for the comprehensive study of auroral displays in both the arctic and antarctic regions. Scientists of 49 nations used a variety of optical and electronic instruments at about 200 stations for their studies while thousands of voluntary observers conducted visual observations throughout the world, and sll of these studies were supplemented by radio echo techniques. Radar reflection studies revealed that auroral ionizaion occurs at heights considerably in excess of the 60-mile lower limit of visual aurora.
The auroral display of February 10-11, 1958, was the most carefully observed and recorded aurora in history. Seen as far south as Cuba, and over an east-west range of at least 6,000 miles, this display was of the rare red variety. Its red portion ranged from 150 to 600 miles in altitude, while the green arcs were at the usual 60-mile level. It was accompanied by strong magnetic and unusual Earth current effects: for example, the potential on the trans-Atlantic telephone cable reached 2,650 volts at the western end, and strong bursts of X-rays were detected on cosmic ray balloon flights from Minneapolis.
A Canadian scientist examines
antennae at a radar station where a study of the aurora
borealis was conducted. Radio waves were bounced off the
aurora and datareceived from the returning waves were
relayed to a central station in Ottawa.
The program in ionospheric physics was carried out by 175 stations operated by scientists of 43 countries, with particular emphasis on the polar regions. The station at the South Pole found that, although ionization reaches a saturation level during the long summer day, the upper ionized layer persists even at total solar absence during the dark winter. Morever, there is a significant 24-hour variation although the Sun remains below the horizon, suggesting an earth effect, probably of the magnetic field, on the ionosphere.
Signifcant findings relating to the ionosphere were achieved in the IGY rocket program. The discovery of X-rays in the lower portions of the ionosphere and its role in radio blackouts was one of these; rockets launched at high northern latitudes showed that blackout is due to a very dense, low portion of the ionosphere. It was also found that this region is denser and lower in height at high latitudes. This information had practical utility in radio communications. A considerable amount of data on atmospheric densities, pressures and temperatures was also obtained.
Launching an Aerobee-Hi research
rocket from Fort Churchill, Colorado, on July 4, 1957.
The rocket carried a radio to send back information about
the Earth's atmosphere from an altitude of about 160
Trumpeters of the Royal Home
Guards examine a model of the Skylark, a high-altitude
rocket developed as part of the British IGY program. The
model was exhibited by the Royal Aircraft Establishment
Radiation experiments conducted by James A. Van Allen and his associates in the Explorer series of U.S. satellites indicated the presence of a zone of intense particle radiation beginning 600 miles above the Earth and reaching out at least 1,800 miles; we now call these zones the Van Allen Belts.
Completed in 1957, this radio
telescope at Jodrell Bank, England, was the largest in
the world at the time, with a receiving bowl 250 feet in
diameter. It was used to track the paths of Soviet earth
Three chains of meteorological stations, almost trisecting the globe from pole to pole, were operated in order to investigate atmospheric currents and the transfer of energy and moisture. Hundreds of other stations provided a weather mapping of the Earth. From all of these stations, balloon-borne instruments were launched at regularly-scheduled times to measure pressure, temperature, density and humidity at predetermined altitudes.
Much was learned about antarctic weather during the IGY. The coldest parts of Antarctica, and thus of the Earth, was found to be a region about 400 miles east of the South Pole, from which a record low of at least -124° F. was reported by Soviet scientists in August 1958. Observations made at Little America were also significant, as they showed that a signifcant warming trend of about 5° F. had occurred in about 50 years. Although this was about one-half that noted in the Spitzbergen-Greenland portion of the arctic, it was important confirmation of a trend that has since been deemed critical in terms of the world's weather.
Two major programs were conducted in oceanography during the IGY. More than 350 tide gauge stations were operated by 25 nations to determine the monthly, seasonal and yearly mean values of sea level. Changes in these values appear associated with an exchange of water between the northern and southern hemispheres and with temperature changes. In the other program, 20 countries operated 80 research vessels in a coordinated investigation of oceanic currents and circulation. These studies had value not only in connection with the oceans themselves, which cover three-quarters of the globe and are vast reservoirs of food and minerals, but in clarifying problems of weather and climate, as the oceans are also great reservoirs for storing heat while their surface currents are related to the principal wind systems.
Two of the most significant new findings were the discoveries of major currents. One of these was located beneath the Gulf Stream, flowing in the opposite direction at a speed of about 8 miles per day and transporting about as much water as the Gulf Stream itself. The second current was found in the Pacific, flowing between 200 and 1,000 feet beneath, and opposite in direction to, the surface equatorial current, carrying about 1 billion cubic feet of water per second.
Echo-sounding techniques were used to map out the ocean bottoms and many new and major topographic features -- including the mid-ocean ridges and deep trenches -- were revealed and mapped. Corings of ocean floors were made to study the structure and history of the sediments.
Studies of glaciers were conducted throughout the world, including the great ice sheets of Greenland and Antarctica. Significant in themselves as major features of the Earth, glaciers are also important to weather and climate study. Because past climatic changes leave behind some of their attributes, preserved in the frozen water of glaciers, considerable effort was placed on the coring program. Annual layers of snow, read in much the same fashion as tree rings, were identified to about the yeat 1700, while the age of the deepest core taken was estimated to be about 1,400 years. Glaciologists were able to determine that far more of the Earth's total supply of water is locked up in the antarctic ice sheet than had been previously believed, and that even a 10% change in antarctic ice would make an appreciable difference to ocean levels,to sea coasts, and to the Earth's heat and water balance.
A glaciologist with the U.S. IGY
team in the Antarctic examines an ice core taken from a
snow mine. The structure of the ice was being studied in
an attempt to determine weather conditions of the past.
Studies in the fields of seismology and gravity were concerned largely with filling in gaps of knowledge concerning remote regions like Antarctica. Seismic techniques allowed scientists to create a fairly detailed map of the land beneath the Antarctic ice and to discover previously unsuspected mountains and mountain chains.
Extensive measurements were made of the Earth's magnetic field by 30 countries at 129 magnetic observatories. The data from these stations permitted a correlation of magnetic events with solar activity, aurora, ionospheric effects, and cosmic ray phenomena.
After the IGY
The success of the IGY led directly to the Antarctic Treaty, which called for the use of Antarctica for peaceful purposes and cooperative scientific research. Perhaps the single most dramatic immediate consequence of the IGY lay in the field of space research. The initiation of satellite research led not only to significant findings about the cosmos but represented the first steps in direct exploration of interplanetary space.
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