Once in a Lifetime Conditions

Propagation Editior, CQ

The Sunspot Story: Cycle 19

The Swiss Federal Solar Observatory has recently announced that the new sunspot cycle, which began during April, 1954, will reach a maximum during the middle of 1957 and will be one of oustanding intensity, with the maximum likely to surpass all others hitherto observed. Because of the direct correlation between sunspot activity and ionospheric characteristics, shortwave radio conditions during the next few years may be better than they have ever been in the history of radio … with the possibility of world-wide DX on Six Meters, around the clock DX on Twenty Meters, direct reception of European and Latin American TV transmissions and other shortwave transmission conditions that occur at best only once in a decade and possibly only once in a lifetime!!

Because sunspots and accompanying solar radiation play such an important factor inshortwave radio communication, an up to date summary of the possible effects of this unprecedented rise in sunspot activity is in order. Consequently CQ has asked its Propagation Editor, George Jacobs, W3ASK, to review the influence of the sun upon the ionosphere and from this viewpoint to discuss the shortwave propagation outlook for the next few years. The discussion is presented in two parts. Part One reviews the origin of sunspots, the effects of solar radiation upon the ionosphere as well as a discussion of the present sunspot cycle trend and a forecast of solar activity expected over the next several years. Part Two, appearing next month, will discuss the rapid rise in sunspot activity in relation to shortwave propagation conditions on the high frequency amateur bands and in the VHF range. The possibility of long distance TV reception and other shortwave transmission conditions will also be discussed.

PART ONE

Sunspot Origin

The exact nature of sunspots, what they are and what causes them, is still rather obscure. Within the past thirty years however, scientific investigations have found that these blemishes on the face of the sun have a direct influence on shortwave radio conditions. Figure 1 is a recent photograph of the sun taken at the U.S. Naval Observatory, Washington, D.C. The sunspots appear as black spots across the sun’s surface. They are believed to be temporary craters caused by violent explosions taking place from time to time on the sun. Sunspots almost always appear in groups. The groups range in visual size from small specks to rather large areas. Sunspots are sometimes large enough to see with the naked eye, provided that a piece of smoked glass or some other type of ray filter is used to protect the eyes from the direct rays of the sun.

The actual size of large sunspots range between 50,000 and 150,000 miles in diameter, an area into which several planets the size of the earth would easily disappear. Even most smaller spots have diameters larger than that of the earth.

Sunspots are known to have been observed by the Chinese as far back as 28 B.C. Long before present day scientists associated these spots with violent disturbances on the sun, they were observed to come and go with a certain degree of regularity. Daily recorded observations of the sun were first undertaken during the 18th century, following the invention of the telescope, and an unbroken accurate record is available that exhibits the trend that develops into the so called 11-year cycle of the sun.