Radio age research, manufacturing, communications, broadcasting, television (1941)

Rocky Point, on the other hand, turns out to be one of the world's best spots for what Dr. Miller terms "optical tranquility." The flat terrain of Long Island usually allows a smooth flow of air, carried by the pre- vailing southerly winds, across the Rocky Point area and into Connecticut before turbulence and thunderstorms develop. Contrary to expectations, the frequent Long Island haze does not normally interfere with their solar photographs and is viewed by the Rocky Point group as a good omen indicating the atmosphere above them is quiet. Getting their best results in the late spring, summer and early fall, the team has had over the past two years an average of 75 days when they made pictures whose detail was limited only by the resolving power of their 6-inch telescopic lens. (Janssen, it is interesting to note took only 25 to 30 comparable shots in a decade.) Twice as many additional days a year are suitable for taking valuable, if not perfect, pictures of the sun. "Give us just two minutes' break in the clouds, and we'll get a shot," says Dr. Miller. May Aid Radio Prediction As their pictures pile up, the team sees emerge a definite pattern of details that may well form the basis of a valuable radio prediction service. Radio engineers have realized for some time that long-range high-frequency communication is feasible because of layers of ionized gas lying in thick spherical shells around the earth's surface. The layers of the ionosphere (a zone lying 50 to 300 miles above us) act as mirrors reflecting radio waves back to the earth's surface. If these layers were fixed in altitude and constant in their electrical reflecting properties, there would be no problem. But this is hardly the case. To circumvent the vagaries of the ionosphere, radio stations must con- stantly change frequencies or reroute circuits. Fortunately, some of the variations in the ionosphere can be anticipated. Seasonal changes and nocturnal changes, for example, have been well charted simply by observing actual radio circuits year after year. But most of the changes are more elusive. Some appear to be com- pletely random. Others may recur more or less regularly, but with unpredictable intensity. Dr. Miller's group is particularly anxious to pin down the latter disruptions because they cause the most distress. How the Sun Affects Ionosphere As Dr. Miller explains it, there are two ways in which the sun can influence the ionosphere. First, by direct electromagnetic radiation — X-rays or ultraviolet rays — which travels at the speed of light from the sun to the ionosphere in 8 minutes. Such bursts of radiation from the sun appear to be the cause of sudden and often complete radio fadeouts called Dellinger fades. For- tunately, these last for only 20 or 30 minutes and never more than two or three hours. The second way the sun is believed to alter the iono- sphere is by sending out actual streams of ionized par- ticles. Such solar bombardments travel more slowly than radiation, taking perhaps two or three days to make the 93 million-mile journey. They are considered a likely cause of the so-called great magnetic storms. These rare but violent disturbances, which may not be felt for years at a time, can knock out radio communications for days and can so disrupt the earth's magnetic field as to cripple wire and cable communications as well. That both radiation and beams of particles can be agents of ionospheric caprices is evidenced by the fact that radiation as felt in a Dellinger fade is disruptive only on the sunny half of the earth. A great magnetic storm, on the other hand, will be felt simultaneously on the light and dark hemispheres, suggesting that the earth is passing through a great shower of particles which have been rapidly dispersed throughout the ionosphere by the earth's magnetic field. Astronomers are fairly well agreed that both these types of disturbance spring from the same phenomenon — solar flares. These sudden, short-lived brightenings of small regions of the sun's surface are usually seen in the neighborhood of sunspots. Flares are often noticed at Minute sechoii of the sun's face, showing granular tex- ture of the solar surface. Large block areas are sun- spots: the tiny black dots are believed to be "spicules" — jets of heated material rising from interior of the sun. 22 RADIO AGE