RADIO AND THE I.G.Y.

New Zealand Listener, Volume 36, Issue 919, 22 March 1957, Page 3

RADIO AND THE I.G.Y.

HE search for new knowledge is as old as Man, and the type of knowledge sought and the methods of seeking have differed not only from century to century, but between one seeker and another. Modern science, however, has changed this, making the thing sought and the method of seeking the same in many countries. But not until the International Geophysical Year had any fullscale co-ordinated research plan utilising the resources of the whole world ever got beyond the stage of a rather remote ideal, In 1882-83, and again in 1932-33, International Polar Years, were held, and some five years ago a third such year was proposed, The proposal found favour with the International Council of Scientific Unions, but instead of the polar regions being the sole object of study, plans were made for a year of study of the whole earth, and LG.Y., the hundred million pound, fifty-nation plan took shape, Ge the Greeks called the earth, but geophysics extends its field of study to the limits of the atmosphere and beyond that to the planets, the moon, and the sun. Many of the more dramatic aspects of. this research period have already been headlined-rockets, artificial satellites, Antarctic stations — spectacular elements which may tend to obscure the work of the thousands of men and women all over the world who will be hunched over their instruments and calculations for the eighteen months of I.G.Y., gathering data that may take more than a lifetime to interpret-and that may never seem to have immediate

practical use, But their work will go on, for facts pure and simple are the first aim of science, and application of secondary importance. For New Zealand I.G.Y. has its own special importance, for the furthering of geophysical knowledge in the southern hemisphere and elsewhere should have great practical significance in two fields at least-the fields of weather forecasting and radio. To the average man, perhaps an even greater frustration than an unintelligible BBC news bulletin, is a Rugby match broadcast on shortwave with most of it failing to arrive. South Africans last year, and New Zealanders in 1949, were only too well aware of this. Long range radio propagation for this reason alone would be of importance to New Zealand. But the most vital reason for its importance is our distance from the major centres of civilisation. Sometimes it is difficult to maintain any radio contact, and the fact that it is maintained is too often taken for granted by the layman who has little knowledge of the difficulties involved. During the I.G.Y. period (July 1, 1957, to December 31, 1958) New Zealand scientists will be concerned with a number of fields of geophysical re- search that may increase knowledge of radio propagation conditions, including the study of the aurora, cosmic rays, geomagnetism, and the ionosphere, At the Dominion Physical Laboratory where a lot of the equipment for the

New Zealand 1.G.Y. work was made The Listener learned something of the problems and the form that this research will take. It is by means of the ionosphere that radio waves are sent over long distances. This "radio mirror" is a series of electrified (or ionised) layers of the atmosphere 50 miles to 250 miles up which reflects waves back to the earth, If these layers remained unchanged radio propagation prediction would be simplified, but they are constantly affected by solar disturbances (sun-spots), changes in the magnetic field of the earth (magnetic storms), auroral displays, meteors, and ionospheric winds. The conditions of the ionosphere, in fact, can depart so far from normal that instead of being a reflecting layer it becomes an absorbing layer, and radio communications are thus reduced or totally blacked out. These ionospheric disturbances can sometimes be predicted, but not their duration or intensity. The difficulties of research are immense. In the case of ionospheric winds researchers will be trying to measure direction, speed and _ height through the behaviour of meteors or through a complicated method of radio sounding at heights that only rockets have reached. Even this is not all the story, apparently, for sometimes there are magnetic storms with no corresponding solar disturbance to be a cause; and sometimes flare-ups on the sun are observed that have no measurable effect on the ionosphere. The problems are so vast and so little understood that only a global effort such as I.G.Y. could gain enough data for any theory to be comprehensive. The period of I.G.Y. has been chosen because it is one of very intense sunspot activity. With observers all over the World making simultaneous measurements and observations, the relationship between the fields of geophysics dealing

with aurora, cosmic rays, geomagnetism, and the ionosphere can be determined on a world basis. The Dominion Physical Laboratory had little more than a year to build their share of the equipment needed, we were told, and the only way to finish in time was to operate almost like a factory, using production-line techniques. Everything to go South had to be conditioned for transport through the Antarctic, allowing for the possibility of equipment being dropped from sledges or standing in slush for ‘long periods. Multiple spares went, too. For the study of auroral zone absorp-tion-and Rugby enthusiasts will remember how noisy and frustrating this "absorption" was during Winston McCarthy’s broadcasts from South Africaa special transmitter has been sent to Scott Base, and six receivers will record its transmission photographically at Mawson, Adélie Land, Port Lockroy (Falkland Islands Dependency), Campbell Island, Hobart, and the I.G.Y. station at Invercargill (see map at top of page), For geophysicists the auroral zones are perhaps the most interesting parts of the ionosphere, and a study of them from all points of view could be very fruitful for the future of New Zealand’s overseas radio circuits. Any increased understanding of the absorption of waves in these zones is of particular importance since transmissions to London, for example, are beamed thirty degrees to the left and right of the Poles. The problem here was to get a "contour picture" of the absorption of waves right around the southern auroral zone; to find, in fact, where the radio "mirror" was dusty and where clear (and, eventually, why this is so). To do this the special transmitter will send signals on four frequencies every hour of the eighteen months of L.G.Y. These signals, reflected at the ionosphere in the region of maximum {continued on page 21)

Radio & The IGY ued from page 3)

auroral activity, will be received by the six recorders which will measure the strength of the signals, and also give some indication of the number of bounces (skips from earth to ionosphere) they have made on the way from Scott Base. Another form = of research into the aurora will be conducted by the Physics Department of Auckland University College. This will be the operation of equipment that will measure the angle of arrival of waves from distant. transmitters. This research should tell whether waves go around the auroral zone when the shortest path is through, or whether, in fact, they do go through. The aurora is an electrical disturbance caused by particles from the sun concentrating at the North and South magnetic poles and exciting the gases in the air-an effect similar to that occurring in a neon tube. But the visual disturbance of waving banners and streamers doesn’t necessarily coincide with the electrical disturbance, we were told, so measurements will be made of both to learn more about their relationship. This will be done at Awarua Radio Station (headquarters of the I.G.Y. team) and at Bluff Hill. At Awarua a spectograph will analyse the colour of the auroral light. From this analysis information can be gained about the reaction between the auroral particles and the particles of the upper atmosphere. This work will be done by a team from the Carter Observatory. Bluff Hill will be the site of the D.P.L. auroral radar equipment used for measuring the electrical disturbance produced by the incoming auroral particles. Radar, being unaffected by daylight or cloudy conditions, is a valuable tool in the study of the aurorae. Of the hundreds of "panoramic ionosondes" working all over the world during I.G.Y., New Zealand will be responsible for four. Three of these are

of a new type developed and designed by D.P.L., and built by the Canterbury College Industrial Development Department. A panoramic ionosonde‘is a device for making a panoramic sounding of the ionosphere. With a marine echo-sounder the time taken for the sound to reach and return from the sea bottom is intepreted into figures for depth. Similarly with the ionosonde, the time lag in the departure and arrival of a pulse indicates the height of the reflecting layers, To get a comprehensive or panoramic picture signals are sent and received through a range of frequencies. Thus a nearly instantaneous picture is received of the reflection heights of the various frequencies up to about 250 miles up where the highest frequencies disappear into space. A high speed of operation is necessary in the ionosonde’s sweep through the frequencies, first for accuracy, secondly so as not to interfere with normal communications. The _ three special New Zealand models, for instance, sweep through the frequency band from one to twenty-two megacycles in a space of seven seconds. Since the effective upper limit of panoramic ionosonde as a research tool is 250 miles, some other method of finding out something about the region beyond is necessary. This method seems to lie in the study of radio "whistlers." These "whistlers" are noises that occur among the crackles and bangs of static heard on a low-frequency radio receiver. One expert at D.P.L. compared them with the second half of a wolf whistlea sound starting in the high frequencies and going right down. Whistlers heard in New Zealand either originate here or on the other side of the earth, in the vicinity of the South Coast of Alaska. A lightning flash, similar otherwise to those in any thunderstorm, may have the special quality that creates the radiation to send a whistler away out into the atmosphere along the lines of force of the earth’s magnetic field and then down to a receiver in New Zealand.

Some of the _ whistiers heard here have started near New Zealand and have been reflected back from Alaska. By an. analysis of the characteristics of these whistlers (through the rate of change of pitch) it is) hoped that information | will be gained about the charged particle density of the outer atmosphere and the’ strength of the earth’s magnetic field. Though this line of research deals with activity that is not merely hundreds but thousands of miles away from, the earth it is still as important as research into the closer atmosphere, for the .forces that give tise to the ionosphere and related phenomena appear to have their origin at least as distant as the sun. Whatever else it achieves, then, in the fields of science and international co-operation, 1.G.Y. should at least remind us that the world we live in is not merely the earth, but the universe.