Magnetic storm

“ These are among the most mysterious phenomena of nature—so subtle and fleeting as to be almost beyond the reach of science. No visible sign do they give of their presence. No clouds darken the heavens; no thunder peals along the sky. Yet strange influences trouble the air. At this very hour, Professor Airy, the Astronomer Royal at the Observatory at Greenwich, reported a magnetic storm of unusual violence. Said a London paper:
"Just when the signals from the Great Eastern ceased, a magnetic storm of singular violence had set in. ”

“ Maunder proved that magnetic "storms" on Earth originate in some way in the Sun. These "storms" are quite irregular (like our storms in the weather) , we should never notice them in ordinary life, but a telegraph clerk finds them a great nuisance; if they are violent and persistent they may make it impossible for him to send or receive his messages. At the time when Carrington and Hodgson noticed that great disturbance on the Sun, of which I spoke early in this lecture, there was a furious magnetic storm on Earth, which was naturally attributed in some way to the solar disturbance. ”

“ The chief criterion at Kew for classifying the days was not so much the mere amplitude of the largest movement, as the general character of the day’s curve and its departure from the normal form. The data in Table XXXVI. as to magnetic storms at Greenwich are based on the lists given by Maunder [35] in the Monthly Notices, R.A.S. A storm may last for any time from a few hours to several days, and during part of its duration the disturbance may not be very large; thus it does not necessarily follow that the frequencies of magnetic storms and of disturbed days will follow the same laws. ”

“ During that time a tremendous sun-spot, exceeding in size the largest of the April spots, was advancing from the edge of the disk to the center. In this country the principal auroral displays were on the nights of the 17th and 19th, and the chief force of the magnetic storm was felt on the 17th. On that day a storm of rain and snow prevailed over most of the Union, and simultaneously with this storm there raged a hurricane of magnetic forces. The effects were similar to those witnessed during the April storm, but more intense. ”

“ It is hardly necessary to add here, that the effect of the aurora borealis, or magnetic storm, is totally unlike that of common or free electricity, with which the atmosphere is charged during a thunderstorm. The electricity evolved during a thunder-storm, as soon as it reaches a conductor, explodes with a spark, and becomes at once dissipated. The other, on the contrary, is of very low tension, remains upon the wires sometimes half a minute, produces magnetism, decomposes chemicals, deflects the needle, and is capable of being used for telegraphic purposes, although, of course, imperfectly. ”

“ In Fig. 2, which represents the spot as it appeared on the 18th, the day after the great magnetic storm, evidences of cyclonic motion are still, perhaps, visible, though they are rather suggested by a comparison of the appearance of the spot with that shown in the previous figure than by any clear indications in the figure itself unconnected with the other one. The roundish, nuclear mass near the center suggests by its form a whirlpool-like motion, but it is difficult on that hypothesis to account for the long, straight channel connecting it with the oblong figure on the right. ”

“ An electric storm is generally confined to a small space beyond the limits of which the condition of the atmospheric electricity remains unchanged. A magnetic storm, on the other hand, p 193 shows its influence on the course of the needle over large portions of continents, and, as Arago first discovered far from the spot where the evolution of light was visible. ”

“ Whatever the exact nature of the aurora, it has long been known to be intimately associated with the phenomena of terrestrial magnetism. Whenever a brilliant aurora is visible, the world is sure to be visited with what Humboldt called a magnetic storm—a "storm" which manifests itself to human senses in no way whatsoever except by deflecting the magnetic needle and conjuring with the electric wire. ”

“ A bright aurora visible over a large part of Europe seems always accompanied by a magnetic storm and earth currents, and the largest magnetic storms and the most conspicuous auroral displays have occurred simultaneously. ”

“ The yearly range may depend on but a single magnetic storm, the largest disturbance of the year possibly far outstripping any other. But taking even the monthly ranges the values for 1893 are, speaking roughly, only half those for 1892 and 1894, and very similar to those of 1898, though the sun-spot frequency in the latter year was less than a third of that in 1893. Ekatarinburg data exactly analogous to those for Pavlovsk show a similar prominence in 1892 and 1894 as compared to 1893. ”

“ It points to zero when the magnetic forces of the earth are in equilibrium, but let a magnetic storm occur anywhere in the world and the pointer will move by invisible power. It detects a close relation between the magnetism of the earth and sun. ”

“ That rapid variations in the earth's magnetic elements, such as often occur on a large scale, as in a "magnetic storm," have at least a share in the production of the aurora is a perfectly reasonable and even plausible hypothesis, long ago brought forward by Balfour Stewart. ”

“ Between the tropics the hour of the day may be known by the direction of the needle as well as by the oscillations of the barometer. It is affected instantly, but transiently, by the northern light.
When the uniform horary motion of the needle is disturbed by a magnetic storm, the perturbation manifests itself simultaneously, in the strictest sense of the word, over hundreds and thousands of miles of sea and land, or propagates itself by degrees in short intervals every where over the earth’s surface. ”

“ Magnetic storms are of extraordinary magnitude and frequency in that region. They stand in the closest relation to the auroral discharges, and the disturbances arc greater as the motions of the light-streams become more lively, and the prismatic colours become more intense. Quiet regular arches, or ray-motions, have scarcely any action upon the needle. In all disturbances the declination-needle moved towards the east. ”

“ The power of sunspots to alter light frequencies shows that these solar storm centers function as enormous magnets. Such magnetic fields are able to hurl charged particles from the sunspot craters out through space to the earth's outer atmosphere, where their ionizing influence produces such spectacular auroral displays. ”

“ It seems to follow that magnetic wave which, passing from north to south, acts in its course upon the counter-trade, producing the storm, or belt of showers, and giving them their southern lateral extension, and will well repay future telegraphic investigation. Its electricity is intensely positive—that of the earth by the action of the storm as intensely negative.
5th. This N. W. wind occurs in all parts of the northern hemisphere, so far as we have data to determine, and its corresponding wind from the S. W. occurs in the southern hemisphere. ”

“ An extensive condensation of vapor going on in the centre, the air becomes lighter there than elsewhere in the revolving disc, and forms a kind of chimney for the denser air below to pass up through; and when this process has been going on for some time the air beneath is sufficiently exhausted to admit of the storm disc descending to the surface of the earth, after reaching which, it takes up a progressive motion and is impelled by magnetic attraction towards the magnetic poles. ”

“ The irregular oscillations when violent are called magnetic storms, and it must be noted that auroral display never takes place except during such disturbances, although a large proportion of the most remarkable magnetic storms are unaccompanied by visible auroræ. ”

“ Meteoric and cometic systems have been visited by the great magnetic wave, and upon the dispersed members of the one and the subtle structure of the other effects even more important may have been produced than those striking phenomena which characterize the progress of the terrestrial or planetary magnetic storms. ”

“ An analogy is found for the charged Leyden jar in the atmospheric condition preceding a thunderstorm when the air between the earth and clouds is under the same strain as the glass.
The theory of molecular magnetization accounts best for the properties of magnets and the study of terrestrial magnetism confirms the coincidence of magnetic storms and sun-spots. All electrical manifestation results in discharge, but current electricity consists in a continuous flow. ”

“ The energy stored by these groups of particles ultimately is responsible for Earth's magnetic storms.
With all this detail, scientists have little more than a sketch —an approximation built on a collection of independent, single—point measurements collected at different times during the past two decades. Boundaries are in constant motion. Changes in one region invariably stimulate subsequent changes or adjustments in other regions. ”

“ Although the earth-core may not be presumed to be an entire moving mass, yet it is known to be in a measure incandescent, and molten. Magnetic storms occur within our earth-crust which sway the needle without, and almost instantaneously manifest their presence over areas of more than half the globe. The same phenomena are undoubtedly present in increased development at the sun. ”

“ Thus the sunspot maximum indicates increased activity at the surface of the sun, which, according to Abbot (1913 and l9132) , is actually sending us increased heat radiation. During the maximum the magnetic condition of the earth is profoundly affected, as evidenced by northern lights, magnetic storms, earth currents, and variations of the earth's magnetic constants. ”

“ Two or three times in 1882 the earth responded instantly with magnetic storms and brilliant auroral displays to the solar activity, but this year the great sun-spots and their accompanying phenomena have shown comparatively little power to affect terrestrial magnetism. ”

“ This period covered five complete sun-spot periods, and the approximate synchronism of the maxima and minima, and the general parallelism of the magnetic and sun-spot changes is patent to the eye. Ellis [23] has also applied an analogous method to investigate the relationship between sun-spot frequency and the number of days of magnetic disturbance at Greenwich. A decline in the number of the larger magnetic storms near sun-spot minimum is recognizable, but the application of the method is less successful than in the case of the inequality range. ”

“ With respect to sun-spots and the magnet, the frequency of magnetic storms, causing oscillation of the needle, gradually increased from a minimum in 1843 to a maximum in 1848, giving a variation of something near 11 years altogether. Schwabe observed the sun-spots for 24 years, and found they had a regular maximum and minimum every five years, and that the years 1843 and 1848 were minimum and maximum years coinciding with the magnetic variation at those periods.
Prof. Loomis considers connexion established between magnetic declination, auroral displays, and sun-spots. ”

“ During sun-spot activity eruptive prominences rise to heights of many thousands of miles and streams of electrons are shot forth with such force that they may possibly even penetrate deeply into our own atmosphere causing disturbances such as magnetic storms and auroras. ”

“ Amongst other theories which ascribe magnetic storms to direct solar action may be mentioned that of Kr. Birkeland, [45] who believes the vehicle to be cathode rays. Ch. Nordmann [46] similarly has suggested Röntgen rays. Supposing the sun the ultimate source, it would be easier to discriminate between the theories if the exact time of the originating occurrence could be fixed. For instance, a disturbance that is propagated with the velocity of light may be due to Röntgen rays, but not to Arrhenius’s particles. ”

“ The relation between the two is evident, from the notorious fact that lightning often renders steel magnetic, and disturbs the magnetism of the magnetised needle, so that in thunder-storms the compass needles of a ship have frequently been seriously injured. The magnetic agency, like electricity, has a general distribution over the earth, but the phenomena differ in different parts of the world, and are subject to periodical differences in the same place, the cause of which is very little understood. ”

“ Hence, at that point, storms do not often originate; the winds are lighter and more variable, and calms are more frequent than at any point, except at the meeting and elevation of the trades, or in the polar regions. Doubtless this state of things is increased by the feebler action of north polar magnetism, and the irregular action of the longitudinal magnetic currents, evinced by the irregular, and often, feeble action of the trades, near their extreme limits. ”

“ Marlin and his fellow-astronomers discussed this matter of the phenomenon's cause, it was its effects that had begun to claim the attention of the world at large. For that increase of the sun's speed was already making itself felt upon Earth. Even the great storms in the sun's mass, those storms that we call sun-spots, indeed, make themselves felt upon Earth by the intense electrical and magnetic currents of force which they throw forth, causing on Earth electrical storms and auroras and strange weather-changes. ”