GREAT MAGNETIC STORM

New Zealand Herald, Volume LVIII, Issue 17784, 18 May 1921, Page 7

GREAT MAGNETIC STORM

SUNDAY EVENING'S AURORA.

SCIENTISTS' EXPLANATIONS.

COLOURS DUE TO VARIOUS GASES.

The auroral display observed on Sunday evening attracted equal interest in the South. The Wellington newspapers describe the phenomenon in terms indicating that its appearance in that latitude differed very little from that seen in Auckland—the sky was suffused with a wine-coloured light to the south, and the whole was shot with shafts and streamers of white ravs reaching to the zenith. Mr. E. A. bhrimpton, chief telegraph engineer, states that the telegraph services throughout the Dominion were greatly affected by the phenomenal magnetic storm. One of the first effects of the storm on Saturday evening was the nullifying of the earth as a return, and | a metallic return had to be substituted by connecting with another wire. The ! greatest difficulty was experienced with ! east and west lines, and the difference of I potential between Blenheim and Nelson ; was well over 60 volts, and at one stape i almost reached 90 volts—an extraordinary v phenomenon. The north-south wires were : not affected to the same extent. Wireless | stations were rendered almost ineffective in an east and west direction,' and com- ; munication was lost with the Chatham ' Islands. At the same time Awanui and I Wellington, working north and south. ! were in easy communication, as was also i Awanui with Suva. | Solar Activity the Prime C I Commenting on-i the phenomena, Dr. jC. E. Adams, Government Astronomer, | remarked on the remarkable association of i aurorae with magnetic storms and sunspots. Observations of more than a cen- ■ tury have confirmed the contemporaneity , of these phenomena and a probable con- | nection. Professor E. Marsden, of Vic- ! toria College, was greatly impressed with j the green tinge in the rays and the indiI cations in the spectrum of the effect obI tained when nitrogen is bombarded with i alpha rays from radium, the suggestion being that the greenish streamers are in some way connected with the alpha particles of helium ejected from the sun. One of the greatest authorities on the Aurora Australis and magnetic storms is Mr. E. N. Webb, who was chief magnetician of the Australian Antarctic Expedition led by Sir Douglas Mawson, 1911-14. Throughout his three years' sojourn in the Antarctic, Mr. Webb studied especially the phenomena of magnetic storms and the Aurora Austral is. When interviewed on Monday, Mr. Webb said the previous evening's display was one of the most brilliant ever seen in these latitudes. It had all the characteristics of the most active forms of Auroral display. The essential feature of the aurora seen in th© Antarctic was the luminous i arch, which might be either a few degrees j above the horizon, or rise as high as 45 degrees or finally to the zenith. From this band of white to yellowish light, streamers shot upward roughly along the line of the magnetic meridian, north and south, toward the zenith. These 1 streamers frequently scintillated and apI peared to move from west to east, and in jan opposite direction. The most active j displays of any auroral phenomenon were | marked by the appearance of decided j colours. Only in intensity and in the I diffusion of the light and colouring did : the local phenomena differ from those | seen in the Antarctic. Twenty Miles Above Earth. The precise cause, said Mr. Webb, of the aurora is still largely a matter of _ surmise and hypothesis, bat it seems [ fairly certain, that the phenomenon is > due to some electrical discharge in the _ extremely rarified portion of the upper j atmosphere. The height of the average auroral discharge as determined by Processor Birkeland in a large number of 1 observations in Norway, ranged from 15 1 to 30 miles. The difficulty of obtaining 2 accurate determinations of height was ) extreme, but it is evident-that the height I is about 20 miles. L " The stream of ions striking the en- ) velope of the earth from the sun," ex--5 plained Mr. Webb, " comes within range 3 of the earth's magnetic fluid, and is 3 probably deflected along the lines of 3 magnetic force toward the poles. In j this way a ' potential', is set tip, which - results in the collection of different } quantities of electricity, which in turn, r under favourable conditions, is discharged, giving rise to the auroral display. This ' discharge is comparable with that which r takes place in a vacuum tube and the colours which are manifest m the aurora are probably due to the prssence of various • gases. During this discharge very heavy electrical currents are set up in the upi-tr atmosphere, and it is die magnetic effect due to the existence of these cm rents which causes the dislocation of tele- ' graphic apparatus."