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The years of the quiet sun

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Astronomers study a greatly magnified image of an area of the sun. Image on the screen has been reflected and focused by a series of mirrors on a giant observatory telescope
© USIS

Scientists in all parts of the world are today studying the results of a vast international research programme into solar activity and its influence on the earth. Here two Soviet geophysicists describe how in 1964-65 the world became one vast laboratory in which scientists from over 70 countries joined forces in a co-ordinated effort to learn more about solar-terrestrial relations.

 Nicolai Pushkov and Boris SiIkin

To the uninitiated, the phrase "years of the quiet sun" may have an odd sound, remindful of some ancient calendar of the East, perhaps of a poetic figure of speech. Yet it happens to be a strictly scientific term which is applied to a great scientific project, recently completed and widely reported.

Men have looked up to the sun as the source of life since the earliest times, and the worship of the sun lasted in many lands until men learned to look for rational explanations of natural phenomena. The sun-god Ra of the ancient Egyptians; Helios, identified with Apollo, worshipped in ancient Greece and Rome; the merry Yarilo of the ancient Slavs (the god of the life-giving forces of nature) these were all held to be incarnations, or embodiments, of the sun.

Centuries were to pass before men learned to base their knowledge on facts rather than faith, and it was only during the Renaissance in Europe that they began to test and experiment in various fields of science. In 1609 Galileo Galilei may be said to have rediscovered the heavens when he first trained his telescope on the moon.

Three and a half centuries have rolled by since then, and we may ask ourselves the question: What have we learned about the sun since those times?

We have learned, for one thing, that the sun does not always remain changeless but is subject to periods of greater or lesser activity. Sunspots, noticed in antiquity and observed by Galileo, appear upon its face with definite regularity, their number increasing over a period of three or four years, after which they decay, solar activity sinks to a minimum, and the sun remains relatively undisturbed. This quiet period continues two or three years after which solar activity again begins to increase. The entire cycle from one maximum to another is completed in a little over 11 years.

Other phenomena besides the sunspots are subject to these cycles: the faculae, or bright regions of the sun's photosphere; chromosphere flares; and prominences, or tongues of flame, leaping hundreds of thousands of kilometers high over the solar surface.

These various phenomena are important and hence of great interest to the scientists. Moreover, they are of no mere academic interest, for the construction of some new hypothesis, for example. Nor is it only that the sun is our nearest star and the only one that admits of direct observation, being merely 150 million kilometers away, whereas the nearest other stars are hundreds of thousands of times more distant.

Concerted effort by thousands of scientists

It is the continuous and varied influence of the sun on the earth that explains our interest, rather than the fact that observation of the sun advances stellar astronomy.

Everyone is familiar with the interferences that frequently occur in radio transmissions. The local broadcast¬ ing station that regularly comes over so clearly all at once begins to fade out and another station, possibly unidentified and far away, comes in. This is all very well if one has been tuned in to a programme of music, but quite another thing in the case of a radio beacon, for in that event ships and aircraft may face distress as a result of confusion in the ether. Or, to take another example, the needle of the compass on which you are accustomed to rely may unexpectedly begin to swing away from a given point, and here again the results may be serious.

In both cases solar phenomena are at the root of the trouble. Solar activity, therefore, and solarterrestrial effects require painstaking observation. We need to know more about the various solar phenomena and to learn how to deal with or, rather, adapt ourselves to the effect of the turbulent activity of the sun that has so direct a bearing on our existence.

The recent international geophysical year (IGY) was a good example of such observation. Within the frame¬ work of its 1957-59 programme a great deal of valuable information was obtained concerning the various terrestrial physical processes and the nature of solar-terrestrial relations. As a result, we have improved our conceptions with regard to our planet's environment.

Valuable as this mass of information may be, its accuracy must be proved by comparison. The IGY happened to coincide with a period of extremely high solar activity. In order to arrive at definitive conclusions, however, we must observe the sun in the less disturbed phase of its cycle as well.

While science has so far been unable to discover precisely what is responsible for changes in solar activity, scientists have learned to fore¬ cast such changes quite accurately on the basis of the 11 -year cycles. Inasmuch as 1957-59 had been a period of maximum solar activity, they were able to predict a period of lessened disturbance in 1964-65.

This prediction gave rise to the idea of organizing an International Years of the Quiet Sun project, or IQSY. When the idea was broached in 1960 by some Soviet scientists, it gained the immediate support of geophysicists from many lands, convened for the Geophysical Conference at Hel sinki. It had become quite clear that the physical phenomena caused by solar activity are on such a scale that they must be studied on an international level, for no amount of restricted, national observation could cope with the problem.

These physical phenomena affect the earth as a whole, and if any reliable conclusions were to be reached, it was obvious that scientists would have to work within the framework of an internationally integrated program¬ me and familiarize themselves with data collected all over the world.

If a chemist or an historian needs to know what his colleagues in other countries are working on, even if simply to avoid duplication of research and to profit from discussion so as to get the right answers, it is doubly important for the geophysicist to do so, for the object of his study is the earth as a whole. Uniformity of experiment, co-ordination of observation and comparison of data collected are of fundamental importance to the geogphysicist; without them it is impossible to unravel phenomena of a universal nature.

In line with the IQSY programme, our planet became one vast laboratory for the scientists to work in. Thousands of geophysicists from more than 70 countries joined forces in a co-ordinated effort to solve the riddles of nature. The project received full support from Unesco and WMO, as well as various international bodies of astronomers, physicists, radio physicists, geodesists and geophysicists; the committee for space research (COSPAR) of the International Council of Scientific Unions and the Special Committee on Antarctic Research (SCAR). W.J.G. Beynon of Great Britain, who was put in charge of the entire project, was requested by the International Committee on Geophysics to work out the general programme of research.

Academies of sciences and other similar institutions in dozens of countries also responded to an invitation to participate in the IQSY, thereby assuring the representation of the five continents, all the climatic zones, many different scientific trends, and countries with very different levels of development, including those with a history of many centuries and those who have just embarked on programmes of economic and scientific development.

Japan and Australia are first to greet the rising sun, and the astronomers of the Tokyo Observatory train their telescopes upon it. As the earth turns upon its axis the sun comes under the observation of the Soviet Far Eastern Solar Service situated on the banks of the Ussuri. An hour or two later this observation is taken up by astronomers in Irkutsk, Alma-Ata, Tashkent and Delhi. As the sun rises over the Caspian it comes within view for Azerbaijan scientists at Perkuli, near Baku, and their Georgian colleagues in the hills of Abastumani. They are soon joined by Kislovodsk, then the Crimea, the town of Krasnaya Pakhra near Moscow, Kiev and Lvov.

The sun is then passed on, as it were, to the astronomers of Potsdam, in the German Democratic Republic, Plzen in Czechoslovakia, Ljubljana In Yugoslavia, Wroclaw in Poland, Pic du Midi de Bigorre in France, and Greenwich in England. On the other side of the Atlantic telescopes are ready for it at the Smithsonian Observatory at Washington, Arecibo in Puerto Rico, Boulder in Colorado and Sacramento Peak in New Mexico, U.S.A., Tonanzintla in Mexico, and Ottawa in Canada. South of the equator, meantime, the watch is carried on, successively, in South Africa, Argentina and Peru, until finally the sun plunges into the Pacific, to rise again over the eastern fringe of Asia.

We have already remarked that the IQSY was not an astronomical project, for we were interested in the effect of solar-terrestrial inter-relationships here, at this end; we wanted to know what kind of impact solar phenomena have on the earth. Astronomical observation of the sun, important as it was, served the participants in the project merely as a point of departure in their work.

The polar regions of our planet are more than any other of interest to the geophysicist, for it is here that the poles of the spherical magnet on which we live are found. It is here that the magnetic storms and polaraurorae produced by the intrusion of charged particles out of the cosmos give displays of particular force. Here, also, we can observe the very peculiar behaviour of the upper charged layer of the earth's atmospheric envelope, the ionosphere, which reflects incoming radio waves. And here, finally, above the endless icy wastes great currents of air often form that affect the weather and climate in even very distant areas.

All these phenomena are directly or indirectly connected with the whimsical moods of the sun and the nature of the electromagnetic and corpuscular radiation emanating from it. To gain a complete concept of the inter-relationships of the earth and its nearest star, therefore, it is necessary to start with observations carried on in the polar regions, where the various features of that concept are particularly characteristic.

That is precisely the reason why the attention of the scientists was focused on the work of the northern most outposts of IQSY at the stations North Pole 12, North Pole 13 and North Pole 14, whose teams carried on through the snowstorms of the endless polar night, studying magnetic storms and polar aurorae in the high latitudes of the Arctic and observing the propagation of radio waves and the behavior of cosmic rays when the sun is undisturbed.

The Antarctic ice-cap at the other pole was made the subject of similar study. At Vostok Station, near to the earth's magnetic pole and cold pole, Soviet scientists enrolled in the project carried on through the winter despite temperatures of 80 degrees Centigrade below zero.

The world's coldest continent became the land with the highest per centage of scientists, a scientists' continent, where co-operation among the specialists from the participating countries reached a record high. At Vostok station and the Mirny Observatory, Soviet scientists worked together with their American, French, German Democratic Republic, Czechoslovak and Hungarian colleagues, while Soviet geophysicists wintered and worked at the American McMurdo station. This fruitful collaboration made it possible to achieve higher levels of perfection in the various schools of science and increase our common fund of knowledge.

Each participating country carried out its own national project, set up within the framework of the overall programme. Considerably more than one hundred "Cosmos" type satellites were launched under the Soviet programme to carry out a wide variety of observations in circum planetary space, precisely where solar phenomena have their first impact on our planet.

Four "Electron" type satellites were launched in the U.S.S.R. specially for IQSY purposes, whose orbits, drawing alternately away from and closer to the earth, covered an extensive part of its immediate environment and were thus able to establish with greater precision the pattern of its magnetic field, to study the streams of particles ejected from the sun and its X-ray radiation, to capture micrometeorites, to study the electrons present in the earth's radiation zones discovered by American and Soviet scientists under the IGY programme and to determine the chemical composition of cosmic rays. American scientists launched several "Explorer" type satellites under the IQSY programme which they used to measure the magnetic field of charged particles; to classify electrons by the direction of their movement and the size of their charge; to study cosmic rays and the recently discovered "solar wind", or particle stream, that fans the earth; and to measure the density of the terrestrial atmosphere on its outer fringes, i.e. where it merges into cosmic space. The American "Oso" and "Ogo" type satellites collected information on the genesis of solar flares and the nature of the particles launched into the cosmos from the solar surface at their genesis.

British "Ariel" type satellites were used to measure micrometeorites and to carry out experiments to deter mine the behaviour of ozone, the "brittle"gas whose genesis in the atmosphere depends on the ultraviolet rays of the sun. "Alouette", the Canadian satellite sent up into the ionosphere, was used to establish the relationship of the ionosphere with the genesis of polar aurorae.

Needless to say, the IQSY programme covered much more than the cosmos: a worldwide network was set up, comprising 240 scientific stations and laboratories for measuring the earth's magnetic field, 180 stations for observing polar aurorae, 270 stations for probing the ionosphere, close to 1,000 meteorological stations for studying the atmosphere, climates and weather, 105 stations for capturing cosmic rays, 110 observatories for recording the solar manifestations responsible for all this diversity of phenomena.

In addition to the cosmic experiments already mentioned, land-based Soviet geophysicists, for instance, effected their observations with the aid of a vast network of stations stretching from the country's western boundaries to the Soviet Far East and from the Kola Peninsula beyond the Arctic Circle and Yakutia to Transcaucasia and Central Asia.

Thousands of Soviet geophysicists attached to the Academy of Sciences of the U.S.S.R. and the academies of many of the Union republics joined this fact-finding scientific campaign. The country's foremost universities co-operated in the effort to penetrate the mysteries of solar-terrestrial effects teachers, researchers and enthusiastic students, the future geophysicists, all joined in this work. No small contribution to the IQSY was made by the scientific bodies of the Soviet Meteorological Service.

The Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation (of the U.S.S.R. Academy of Sciences) brought into prominence as an IQSY centre the small town of Krasnaya Pakhra near which it is situated in the Moscow countryside.

One of the Institute's departments was continually on the move the schooner "Zarya", the world's only non-magnetic vessel. The "Zarya" carried the IQSY flag over tens of thousands of miles, as it sailed the Baltic, North, Greenland and Norwegian Seas and the wide reaches of the Atlantic Ocean down to the equa¬ tor, sounding and measuring to procure the data to be used for making precision marine charts of magnetic declinations.

A very extensive network of scientific stations and observatories was deployed by the geophysicists of the U.S.A. to carry out the diverse observations provided for by the IQSY programme. This network covered the country from Point Barrow in Alaska down to Cape Kennedy in Florida.

Work upon the project was also carried on by American scientists in Antarctica: at the McMurdo Observatory, at eight stations built specially for electromagnetic observation, and at the Amundsen-Scott Station, situated at the geographic South Pole, or as far down as one can go on our planet.

Interesting experiments in the field of polar aurorae and cosmic rays were carried out in the southern ocean by the American expeditionary vessel "Eltanin". In many lands as widely scattered as Iceland, South Africa, Morocco and Japan, American scientists carried on observations in cooperation with local geophysicists.

British scientists carried out their study of atmospheric physics and various weather phenomena in their relationship to the Quiet Sun at stations on the British Isles, on board four special weather ships cruising the North Atlantic and on board the famous research vessel "Discovery" assigned to the Indian Ocean. The earth's magnetic field was studied by home stations, by stations on Mau tius Island and on board the scientific ship "Vidal".

Solar observations from land, sea and space

The British network of stations designated to observe the polar aurorae stretched from North Scotland to Halley Bay in Antarctica, while the stations studying the ionosphere were scattered from Edinburgh and Sheffield to Singapore and the Weddell Sea that washes the Antarctic ice-cap. The English climate did not appear to interfere with radio observation of the sun, which was successfully  carried on with the aid of the giant 75-metre radio telescope of the Jodrell Bank Observatory. A regular battery of scientific instruments was set up on the Woomera Range in Australia for launching the British "Skylark" rockets into the upper layers of the atmosphere.

A substantial contribution to the project was made by the scientists of the Federal German Republic. The Max Planck Institute of Aeronomy built an observatory in the Harz Mountains, which was used for the observation of satellites and the study of the behaviour of the ionosphere. The Scherhag Institute in Berlin undertook to prepare daily weather charts for the entire northern hemisphere, and this made it possible to study the effect of solar perturbations on stratosphere temperatures.

An interesting and important programme was implemented by the scientists of the German Democratic Republic. Ozone, in its relationship with the fitful behaviour of the sun, was studied at Potsdam, magnetic variations coinciding with the days of an undisturbed sun were recorded at Niemegk; and studies in the field of wave propagation were carried on at Kuhlungsborn.

A major part of the IQSY programme was Implemented by the geophysicists of Czechoslovakia, Japan, France, India, Canada, Poland, Italy and Australia. While space does not permit mentioning their individual contributions, it may be said' that the work of each was integrated in this international effort, and each carried an important share.

The Information on solar-terrestrial effects collected over the period covered by the IQSY in such widely scattered areas as Yakutia in Soviet Siberia, the Peruvian Andes, Antarctica and the Island of Capri, will serve, in all the 70 participating countries, as a point of departure for scientific theorizing in search of explanations for worldwide physical processes. While the most important conclusions still remain to be drawn, some have already become apparent. Thus, while the sun was undisturbed polar aurorae were rarely observed outside the Arctic and the Antarctic. There were fewer magnetic and ionospheric storms to cause compass deviations and black out radio communication. A deterioration was observed of the flux of X-rays and ultraviolet rays and the shower of incoming charged particles. Changing conditions in the upper atmosphere brought about a measure of change in weather phenomena. Changes were also observed in the pattern of radiation zones encircling our planet.

Rockets yielded a great amount of information on the upper layers of the atmosphere, which is precisely where the earth's atmospheric envelope receives most of the impact of the various solar emanations. More information is now available on the flux, reflection and distribution of solar heat; on the movement of large air masses; on the behaviour of cloud canopies; and on the effect of solar activity on the density of the upper atmosphere.

The expedition on the "Zarya" discovered extensive magnetic anomalies in the North Atlantic, off the coasts of the British Isles. The study of polar aurorae has dispelled some of the mystery surrounding the chemical composition of the upper atmosphere, which was discovered to contain atomic hydrogen and helium of terrestrial origin. It Is now clear that the chemical composition of the outer ionosphere Is much more complex than hitherto thought, and that even short radio waves can migrate repeatedly from hemisphere to hemisphere following the terres¬ trial magnetic lines of force. Scientists were able to establish that the intensity of the cosmic rays, and more particularly that of their component low charge particles, roughly doubles during the period of an undisturbed sun, while the flux of positive ions dwindles to half Its volume.

It is impossible to enumerate all the scientific achievements under the IQSY programme, all the more so as progress in the field of geophysics is nowadays almost too rapid to follow.

The IQSY project is an excellent example of the kind of joint effort on an international scale that is required by the very nature of the field under study. Perhaps its greatest significance lies in the fact that it has brilliantly demonstrated the fruitfulness of businesslike co-operation among the scientists of all lands.

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Nicolai Pushkov

A prominent Soviet geophysicist (and winner of the Lenin Prize), Nicolai Pushkov is director of the Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation of the U.S.S.R. Academy of Sciences. He is also a vice-president of the Committee for the International Years of the Quiet Sun (IQSY).

Boris Silkin

An eminent researcher, Boris Silkin is a member of the Soviet Geophysical Committee (Presidium of the U.S.S.R. Academy of Sciences). He took part in the International Geophysical Year and the IQSY, and has written books and studies on these international research projects.