Aurora and the solar corona. Mr. Norman Lockyer’s ‘Solar Physics.’
Mr. Norman Lockyer, in his ‘Solar Physics,’ a work of 666 pages, gives but little space to the Aurora. The index comprises:—“Aurora Borealis, connexion with sun-spots, pp. 82-102.” “Affirmed coincidence of spectrum with that of the corona, pp. 244, 256.”
Extracts from as to Aurora’s connexion with sun-spots and with solar corona.
Page 82. After referring to Gen. Sabine as having shown that there are occasional disturbances in the magnetic state of the earth, and that these disturbances have a periodical variation, coinciding in period and epoch with the variation in frequency and magnitude of the solar spots as observed by Schwabe, the author proceeds to state, “and the same philosopher has given us reason to conclude that there is a similar coincidence between the outburst of solar spots and of the Aurora Borealis.”
Page 102. “We have also shown that sun-spots or solar disturbances appear to be accompanied by disturbances of the earth’s magnetism, and these again by auroral displays.”
Evidence of American observers on nature of the corona considered.
Page 243. “What, then, is the evidence furnished by the American observers on the nature of the corona (solar)? It is bizarre and puzzling to the last degree. The most definite statement on the subject is that it is nothing more nor less than a permanent Solar Aurora! the announcement being founded on the fact that three bright lines remained visible after the image of a prominence had been moved away from the slit, and that one (if not all) of these lines is coincident with a line (or lines) noticed in the spectrum of the Aurora Borealis by Professor Winlock.” Mr. Lockyer then adds, that amongst the lines he had observed up to that time, some forty in number, this line was among those which he had most frequently recorded, and was, in fact, the first iron line which made its appearance in the part of the spectrum he generally studied, when the iron vapour is thrown into the chromosphere.
Mr. Lockyer’s conclusion adverse to the question being settled.
Hence he thought he should always see it if the Aurora were a permanent solar corona, and gave out this as its brightest line, and on this ground alone should hesitate to regard the question as settled.
Prof. Young’s communication to ‘Nature.’