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SOUTHERN ASTRONOMERS and
AUSTRALIAN ASTRONOMY


AURORA AUSTRALIS.

By H. C. RUSSELL, B.A., C.M.G., F.R.S.

[Read before the Royal Society of N.S.Wales, November 3, 1897.]
• Numbers in [ ] brackets are the original page number from source.

Written :


GENERAL INTRODUCTION



AURORA AUSTRALIS.


INTRODUCTION

WITHIN the last few years associations of persons, interested in the study of auroral displays have been formed, in the countries which surround the North Pole, with the common object of investigating the phenomena presented. Many new and important already been brought to light, and something has been done towards connecting the phenomena about the North and South Poles. I have done a little by collecting and publishing the reported Aurora Australis, but I feel that what has been done is not enough, and that if these records are published in our Societys volume that they will reach a much wider circle, and further will, I hope, lead all those who see the Aurora Australis to report it.

Sailor generally believe that the Aurora is a sign of coming bad weather, and they are keen observers. Nearly all the information about displays come to me in ships logs, but we want also the help of those on shore who are in good positions for observing. Two of the auroral displays in April this year were unusually magnificent, and one of them which I want to bring before you this evening was the finest ever seen in the southern hemisphere, so far as I have been able to ascertain.

This was observed by Capt. Campbell Hepworth, R.N.R., of the R.M.S. Aorangi, who sent me the following description of what he saw, which reads more like the description of an aurora seen in the far north by arctic observers, than what we should expect to be seen between the Cape of Good Hope and Australia, where the Aorangi was in 96° East and 47° South, when the aurora was seen :-

BRIEF NOTES OF A FINE AURORA SEEN ON APRIL 20, 1897.

It was first seen as a diffused light over the southern horizon, like the light over a distant city which is illuminated by electric [2] light, from this light flashes or rays soon shot upwards, and in every direction increasing in length and brilliancy, until at 7·30 p.m., they were shooting across the sky to within 30° of the northern horizon. Cones and circles of light travelled rapidly over the whole sky, and flashing beams of intense light darted from one to the other. This continued until 8·30 p.m.

A remarkable change then occurred, the sky being cloudless, moon and stars shining brilliantly ; an arch of bright green light, fading oft into yellow, formed over the southern horizon rose rapidly to a higher and higher altitude, and was followed by similar arches in regular succession, until there were six arches quite distinct, their apices being from 10° above the southern horizon to 60° above the northern horizon ; these arches appeared to be formed of vertical bars of light side by side, thus building the arches of light, which varied in width from 5° to 20° each, and all of them were bright green and yellow at the tops of the arches, and of a rosy hue where they touched the horizon. Subsequently these arches changed their shapes in all parts of the sky, forming remarkable bands of light, and in some cases patches of light, which in all cases seemed to be fragments of the original arches, from the curves they presented, with the exception of two places, where the bands seemed to meet at right angles.

Up to 8·30 p.m. the flashes of light which came from the southern centre of action seemed to shoot along the eastern horizon, and then rise up like bands of light on hinges at the north and south points of the horizon, sweeping across the sky to the west ; after 8·30 the flashes of seemed to shoot vertically upwards. A circle of light about 30° in diameter now formed about the zenith, and the rays of light before referred to seemed to rise up to the circle, but did not touch it exactly at right angles, but slightly tangential, so much so that they suggested the picture of a cyclonic centre with winds blowing tangentially round it. 1. [3]

Pendent overhead one could see the cloudless blue in the centre of the ring-shaped tassel of coloured light. Later a spiral cord of light, shewing three perfect coils formed at the zenith, and look the ring of light, travelled westward, while to patched of brilliant light, spiral in form like a waterspout, were flaring in the west.

The barometer had been at forty-eight hours prior to the display abnormally low, between 28·90′ and 28.80′ (Board of Trade Barometer) and the wind from W.N.W. strong. A fresh to moderate gale had been blowing previously.

In the midst of the grand display just recorded, a remarkably bright meteor, starting from Canis Major in the north-west, travelled slowly across the sky to the south-west, discharging at intervals fragments of colour, and thus adding to the splendour of the scene, A special feature of the display had a motion to the west like a changing panorama. after 9·15 p.m. the aurora was less brilliant, but burst into greater activity a few minutes afterwards, more especially in the northern semicircle. The display lasted until 9·45, gradually fading after 9·30 p.m.

This short account was prepared by Commander Hepworth hurriedly, while he was getting ready for the first voyage of the new service with the Aorangi. He expressed his intention of sending a fuller account of the aurora to the Royal Meteorological Society, London, as soon as he could find leisure to write it.

In the mean time the third officer of the Aorangi, with the permission of the commander furnished me with the following account based on his own observations while on the deck, and those of the chief, third and sixth engineers who were very much interested in the aurora.

Mr. Bayldon, third officer, says, Herewith I send to you our account of the aurora. It is compiled from the notes I made at the time whilst actually watching the scene, and from an account written next day, and it has been overhauled by our chief, third, and [4] sixth engineers, who were all interested spectators, and nothing in the account was allowed to pass unchallenged.

In conference with Mr. Bayldon before he wrote the account for me, I asked him if possible, to compare what he saw with the pictures given in The Aurora Borealis, by Alfred Angot (1896 London), and the references are to the plates in that work.2.

He says, If the arches in the frontispiece were more regular they would fairly well represent the rising of our arches, but ours were much farther apart, and were most perfect when near the horizon. Figures 2 and 3 resemble the bands of light which we noted before 8·30 p.m., but ours were much fainter, and moved from east to west as if they were arches pivoted at north and south points. Figure 6 resembles many conditions we saw after 8·30 p.m., while figure 7 fairly represents the rays we saw radiating in all directions from the southern horizon, though with us they did not radiate with anything like the regularity and profusion shewn in the diagram. Figure 8 resembles very many patches of auroral light which we saw after 8·30 p.m., excepting the dark lines, which we did not see. The lower point of No. 8 might answer to what we have called a water spout. Figures 12, 13 and 14 (without the hook) were many times illustrated, especially in the circle and spiral chord, which we have described, though we saw nothing approaching figure 13 in grandeur.

There is one feature of the illustrations which strikes us all as very different from what we saw, and that is they all shew the lower edge of the arches as defined and the upper one as shading off into drapery. In all that we saw, this was reversed ; with us the upper edge was defined and the lower edge shaded away into drapery.

The aurora first became visible at 6·30 p.m., on April 20th, 1897 (apparent time at ship), as a bright diffused light in the southern horizon, above a heavy bank of cumulus, the sky being perfectly elsewhere and stars shining brightly. Soon separate and beams of light flashed from this diffused light in every [5] direction — horizontally, vertically, and obliquely-like electric search lights increasing in length, breadth and vividness until, at 7·30 p.m., the vertical beams reached to within 10° of the northern horizon. Faint beams of light during the same time also formed in the east, and swept rapidly across the entire sky from east to west, passing through the zenith and reaching from the southern to the northern horizons. Cones and patches of intense bright light also appeared in all directions, discharging beams and flashes of light incessantly from one to the other, like electrical discharges or lightning. This continued until 8·30 p.m. The moon rose at 7·18 p.m., and every particle of cloud disappeared, the night being very bright and clear with moderate north-west breeze. Barometer 29·00; thermometer 44°.

At 8·30 a most remarkable change occurred ; until then the aurora had been simply composed of white light of homogeneous structure, now colours and hues of every description appeared suspended vertically in the sky. A narrow arch– the upper edge perfect in outline as a rainbow, the lower edge serrated and fringed, owing to the difference in length of the beams or bars of which it was composed-suddenly appeared 15° above the southern horizon of rich green and yellow hues, and rapidly rose to a higher altitude. Another of the same description formed and followed it, others followed in similar order until there were distinct arches of drapery, the first tier then being about 60° above the northern horizon. They were long narrow arches from 5° to 20° wide and made up of vertical stripes and streams of light, like Mr. Angots frontispiece, which were suspended in a pendulous position in the sky, the upper half of the drapery being bright green and yellow, while the lower half was of pink and roseate hues. Rapidly the arches changed and contorted into fragmentary scrolls of many shapes ; in all parts of the heavens other such formations appeared cloud-like and evanescent to north, south, east and west, in some cases lasting only a few seconds, in others for a minute or two ; all of the brightest green, yellow, and roseate [6] hues, changing their shape and position with almost inconceivable rapidity. Dark arches also were visible.

When any such drapery appeared directly overhead, only a gorgeously bright, very narrow, sinuous line was presented, but when viewed obliquely, the fringe-like depth of the scroll, with its different shades of colour was most beautifully apparent. Every formation was arranged in some sort of curve or spiral (excepting two which formed two distinct right angles); every one directly it appeared darted away to the westward, and in every one there appeared to some observers to he a rotatory movement amongst the coloured particles of which the drapery was composed, whilst to others this movement appeared to be wave-like 5 horizontal flashes continually darted from one nebulous mass to another. To add to the splendour of the scene, at 9·10 p.m. a remarkably bright meteor slowly passed across the western horizon from Canis Major, bursting into many coloured fragments and passing underneath several of the fragmentary parts of the aurora.

In such an extensive and ever changing panorama it is impossible for one observer to accurately describe the many interesting aspects which so continually presented themselves, and so rapidly vanished. Each one would catch a glimpse of something different, and could only form a very general idea of what actually took place. However three formations were so brilliant as to be noted by all— First at 9p.m., when a magnificent circle of light appeared directly around the zenith, with a diameter of about 20° formed as before of draped rays of beautifully tinted light. Looking upwards through this circle it was plainly seen that these rays were not strictly perpendicular, but slightly slanting downwards from left to right, and the rotatory or wavelike movement of every particle was most apparent. Secondly at 9·5 p.m. when a spiral scroll of three chords arranged itself around a nucleus of a few degrees towards the northward of the zenith Thirdly, at 9·15 p.m., when two forms of exceptionally bright light appeared like waterspouts 10° high in the western horizon, which was probably a perspective view of a sinuous line reaching below the horizon. [7]

After 9·17 p.m. the scene lost much of its brilliancy only to burst again into magnificent activity at 9·20 p.m., being brightest and most intense in the northern semicircle, and lasting until 9·30 p.m. After this the splendour gradually faded away, through occasional discharges of bright flashes or the appearance of clouds of diffuse light continued until 9·45 p.m., again being homogeneous nature.

Generally throughout the display, first magnitude stars were visible, shining through the aurora, though at times is brilliancy was so radiant as to totally absorb their light. The moon was bright with no halo around. After 10 p.m. the sky rapidly clouded over with cirrocumulus and cumulus, and slight rain fell the breeze falling very light. Throughout the previous day (April 19), the weather has been cloudy and unsettled, with a fresh north-west gale, which gradually moderated on the 20th. During the night of the 20th, moderate to light north-west breezes prevailed. At 8 p.m. on the 21st the wind rapidly freshen to a moderate south-west gale, which continued until the evening of the 22nd.


A second display of the Aurora Australis was witnessed from R.M.S. Aorangi throughout the whole night of April 23rd, 1897, from 7·15 p.m. until 4 a.m. April 24th, the ship being in Lat. 45° South, Long. 119° to 121° East ; barometer 30·25 ; thermometer 45 °F. Owing to the sky being so cloudy, with cumulus and showers occurring at intervals, but little could be noted of this aurora. A diffuse light prevailed over the southern horizon throughout the night. At 9 p.m. two arches of more intense light appeared above the former southern horizon at the altitudes of about 20° and 45°, they were of a pale greenish hue. At 11 p.m. bright flashes in a vertical direction were apparent for a few minutes, all in a homogeneous structure. Throughout April 23rd, the wind was gradually moderating from a fresh south-south-west to light southerly breeze at midnight. At 8 a.m. on the 24th again freshened to a moderate south-south-west gale which continued until noon of the 25th. [8]

LIST OF AURORAS 1896-7.

Date. Name of Ship, S. Lat. E. Long. Notes.
Aug. 21, 1896 Hawkesbury 48   2 100 21 Aurora australia at midnight
,, 22, ,, ,, 48   1 101 20 Aurora at 4 p.m.
,, 23, ,, ,, 47 49 106 31 Aurora at midnight no other particular details given.
Oct. ,,   Thermopylæ 46 44 114 06 At midnight the aurora was very vivid.
Jan.   2, 1897 Damascus 48   9 107 10 Aurora australis visible.
Mar.  1,   ,,   Hawkesbury 51   4   73 49 Ditto ditto.
,,   5,   ,, 51 34   93 53 Ditto ditto.
,,   ,, ,, 51 42   95 23 Ditto ditto.
April 20,   ,,   Aorangi 47 25   96 40 Special notes in text
,,   23,   ,, ,, 45   0 119−121 Ditto ditto.
Aug.   1,   ,, Damascus 46   0 108 40 At 8 p.m. cloudy, Aurora australia visible.

Endnotes

1. This is more like the Aurora observed in Melbourne 2/9/1858, than any other I know.

2. See https:// archive.org/details/auroraboreali00angouoft


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