The occasional observation of sun spots is an avocational activity of interest to any intelligent person; and particularly so, in view of correlation possibilities, to anyone interested in the weather. Very little apparatus is needed for a start. Even the poorest sort of opera glass, field glass, or telescope will reveal spots when solar activity is high. It is necessary, of course, to use some sort of light-absorbing screen between the sun and the eye — perhaps a piece of glass blackened over a candle, or better, a thickness or two of overexposed photographic film.
Some of the better binoculars and telescopes can be obtained with eyepiece filters of dark glass, which slip on conveniently and cut down the excessive light. By turning the eyepiece of a large hand-glass or a small telescope to a suitable focus, the solar image (spots and all) can be projected on a shaded piece of white paper and traced over in pencil. Often seen near spot groups on the sun are bright ‘faculae’ (named from the Latin word for ‘little torch’), which appear as bright, lacy patterns on the solar surface.
It is not possible to see them at all without a fairly good telescope or a very excellent hand-glass; and even with one, they are visible only near the sun’s edge, or limb, where the background of solar surface appears darker. The faculae are supposed to be ridges or elevations in the photosphere, and it seems quite reasonable to assume that they are ‘hot spots’ in relation to most of the solar surface -areas which radiate more than their share of total energy, and much more than their share of powerful ultra-violet.
In addition to the faculae, there are bright clouds of calcium called ‘flocculi’ (Latin ‘tuft of wool’); and also dark flocculi, which are clouds of calcium and hydrogen at high levels in the chromosphere. These dark flocculi, incidentally, are sometimes observed being drawn into the upper levels of sun-spot vortices (Kedzie 61-62).
While the dark and easily seen sun spots have been assiduously observed and studied for generations, all too little intelligent human attention his been directed towards the faculae or solar flares – the solar hot spots that bombard the earth’s outer atmosphere with monstrous intensities of ultra-violet radiation, and colossal quantities of high-speed free electrons and protons. Scientists without number have tried to correlate magnetic storms, auroras, radio reception, and even weather with the day-to-day or year-to-year rise and fall of the sunspot numbers – and with striking success in some fields.
But the success might be even more striking, particularly in the most difficult and complex field of all solar-terrestrial correlation: world weather – if researchers paid less attention to sun-spot numbers and areas; and more attention to favulae areas and brightness indices. Usually the rose-tinted chromosphere of the sun is blotted out by light from the blinding photosphere. But during a total eclipse, or viewed through the spectrohelioscope, its ruddy ring becomes visible. It is then seen to be very irregular at its outer edge, with great flame-like prominences often rising a hundred thousand miles or more above the solar surface.
Quiescent prominences often keep their general form for days on end, and are probably caused by the luminous excitation of diffused, highlying clouds of helium, calcium, and hydrogen. But prominences may become eruptive, and are then gigantic explosions wherein the metallic vapor travels outward at a hundred or more miles a second, reaching heights of two or three hundred thousand miles. These great solar flames dwarf the largest earthly volcano into the comparative insignificance of a toy spitfire (Pugh 29-30).