scholarly journals On the variable intensity of ter­restrial magnetism, and the influence of the aurora borealis upon it

1837 ◽  
Vol 3 ◽  
pp. 37-38
Keyword(s):  
Magnetic Force ◽  
The Sun ◽  
South Pole ◽  
Variable Intensity ◽  
Aurora Borealis ◽  
The North ◽  
The Earth ◽  
Northern Latitudes ◽  
Snow Storms ◽  
Magnetic Needle

The author gives the results of a series of observations on the vibrations of the magnetic needle, which he undertook last summer, for the purpose of ascertaining whether the intensity of its directive force is affected by the changes in the earth’s distance from the sun, or by its declination with respect to the plane of its equator. He observed that the magnetic intensity is subject to frequent variations, which are sometimes sudden, and of short duration. These anomalies he has been unable to refer to any obvious cause, except when they were accompanied by the appearance of the aurora borealis, which evidently affected the needle on many occasions. He also thinks that the vibrations of the needle became less rapid with a moist atmosphere, and more so when it was very dry. Changes of the wind and snow storms appeared also to be attended with fluc­tuations in the intensity of the magnetism. He endeavoured to ascertain whether there existed any decided and constant difference in the directive force of each pole; conceiving that, on the hypothesis of a central magnetic force, the north pole of the magnet would, in these northern latitudes, be acted upon with much greater energy than the south pole. From his observing that the relative intensity of the two poles is not always the same, he infers the probability of the earth’s magnetism being derived from the agency of electric currents existing under its surface as well as above it, and that the rapid fluctuations in its intensity are owing to meteorological changes. The author is led to conclude that the aurora borealis is an elec­trical phenomenon, and that it usually moves during the night nearly from north to south, and in an opposite direction during the day ; that it is of the nature of positive electricity; and that its elevation above the earth is much greater than a thousand, and perhaps thou­sands of miles.

Les causes du magnétisme terrestre prouvées

1851 ◽  
Vol 5 ◽  
pp. 978-979
Keyword(s):  
Diurnal Variations ◽  
The Sun ◽  
The South ◽  
Terrestrial Magnetism ◽  
Aurora Borealis ◽  
The North ◽  
The Earth ◽  
Secular Variations ◽  
Magnetic Needle

The author considers the elements of terrestrial magnetism to be, that the force with which the magnetic needle maintains its position is not everywhere the same, and that its declination and inclination vary from one region to another. These elements, he states, undergo very different modifications, which may be reduced to the following:― 1. Variations with reference to the position of the sun to the south or to the north of the equator; 2. diurnal variations in different regions of the earth; 3. disturbances which proceed from changes of weather, and from volcanic irruptions, and those which are observed during the appearance of the aurora borealis; 4. secular variations.

scholarly journals XI. On the variable intensity of terrestrial magnetism, and the influence of the aurora borealis upon it

1831 ◽  
Vol 121 ◽  
pp. 199-207
Keyword(s):  
The Sun ◽  
Variable Intensity ◽  
Terrestrial Magnetism ◽  
Aurora Borealis ◽  
Magnetic Attraction ◽  
Variable Force ◽  
Abstract Principle ◽  
Planetary Orbits ◽  
Magnetic Needle

In the annexed Table are given the results of a series of observations on the vibrations of the magnetic needle, which I undertook last summer, for the purpose of ascertaining whether its intensity is or is not affected by the changes in the earth’s distance from the sun, or by its declination with respect to the plane of his equator; for, if we refer the nodes of the planetary orbits to this plane, there appears to be so considerable a degree of coincidence in most of them, as would seem to imply the existence of a more definite law than we are ac­customed to attach to the abstract principle of gravitation. I am not at present prepared to say much respecting this part of my investigation; but I have obtained results, which appear to be interesting, relative to the variable force of the magnetic attraction, and the action of the aurora borealis on the direction and intensity of the needle.

Observations and experiments on the daily variation of the horizontal and dipping needles under a reduced directive power

1833 ◽  
Vol 2 ◽  
pp. 197-197
Keyword(s):  
Daily Variation ◽  
Considerable Extent ◽  
The Sun ◽  
The North ◽  
The Earth ◽  
Fixed Direction ◽  
Vibratory Motion ◽  
Daily Change ◽  
Magnetic Needle ◽  
North End

By disposing magnets so as partly to counteract the influence of the earth’s polarity on a magnetic needle, the author suspected that its daily variation might possibly exhibit itself in a very increased degree; and in experimentally prosecuting the idea, he found it to be the case to a very considerable extent in regard to the horizontal needle; and to take place also, though less satisfactorily, with the dipping-needle. In the former experiment a finely suspended horizontal needle was used, the directive power of which was reduced by two magnets, properly placed for the purpose; a deviation of 3° 15' was thus obtained at 11 a . m., which decreased to a late hour in the evening. The needle was kept in the same position for three days, with some change of directive power, with similar general results. After adverting to a difference in the direction of the variation in and out of doors, Mr. Barlow details the results of several experiments, which lead him to the following conclusions :—that while the north end of the needle is directed to any point from the S. to N. N. W., its motion during the forenoon advances towards the N .; and while directed towards any point between the N. and S. S. E. its motion is still to some point between the N. and N. N. W., so that there ought to be some direction between those limits in which the daily motion is a minimum: but whether this is a fixed direction during the year, or whether it has any vibratory motion as the sun changes its declination, is a question requiring further experiments to determine. Another conclusion which the author draws is, that the daily change is not produced by a general deflection of the directive power of the earth, but by an increase and decrease of attraction of some point between the N. and N. N. E., or between the S. and S. S. E.

On the magnetizing power of the more refrangible solar rays

1833 ◽  
Vol 2 ◽  
pp. 263-265
Keyword(s):  
The Other ◽  
The Sun ◽  
South Pole ◽  
Flint Glass ◽  
The North ◽  
Exposed Part ◽  
Uncovered Part ◽  
Almost All ◽  
Magnetic Needle ◽  
Solar Rays

In the year 1813, Professor Morichini, of Rome, announced that steel exposed in a particular manner to the concentrated violet rays of the prismatic spectrum becomes magnetic. His experiments, however, having uniformly failed in other hands, had ceased to excite gene­ral attention; especially in this country, whose climate is usually so unfavourable for such researches. The unusual clearness of weather last summer, however, induced Mrs. Somerville to make the attempt. Having, at that time, no information of the manner in which Prof. Morichini’s experiments were conducted, it occurred to her, however, as unlikely that if the whole of a needle were equally exposed to the violet rays, the same influence should at the same time produce a south pole at one end, and a north at the other of it. She therefore covered half of a slender sewing needle, an inch long, with paper, and fixed it in such a manner as to expose the uncovered part to the vio­let rays of a spectrum, thrown by an equiangular prism of flint glass on a panel at five feet distance. As the place of the spectrum shifted, the needle was moved so as to keep the exposed part constantly in the violet ray. The sun being bright, in less than two hours the needle, which before the experiment showed no signs of polarity, had become magnetic; the exposed end attracting the south pole of a suspended magnetic needle, and repelling the north. No iron was near to disturb the experiment, which was repeated the same day, under similar circumstances, with a view to detect any source of fal­lacy in the first attempt, but with the same result. The season continuing favourable, afforded daily opportunities of repeating and varying the experiment. Needles of various sizes (all carefully ascertained to be free from polarity), and exposed in va­rious positions with regard to the magnetic dip and meridian, almost all became magnetic; some in a longer, some in a shorter time, va­rying from half an hour to four hours, but depending on circum­stances not apparent. The position of the needles seems to have had no influence, but the experiments were generally more success­ful from 10 to 12 or 1 o’clock than later in the day. The exposed portion of the needle became (with a few exceptions) a north pole, exceptions possibly attributable to some predisposition in the needle, itself to magnetism too slight to be observed. The distance of the needle from the prism was varied without materially varying the effect. It was found unnecessary to darken the room, provided the spectrum was thrown out of the direct solar rays.

Observations and experiments on the daily variation of the horizontal and dipping needles under a reduced directive power

1833 ◽  
Vol 2 ◽  
pp. 197-198
Keyword(s):  
Daily Variation ◽  
Considerable Extent ◽  
The Sun ◽  
The North ◽  
The Earth ◽  
Fixed Direction ◽  
Vibratory Motion ◽  
Daily Change ◽  
Magnetic Needle ◽  
North End

By disposing magnets so as partly to counteract the influence of the earth’s polarity on a magnetic needle, the author suspected that its daily variation might possibly exhibit itself in a very increased degree; and in experimentally prosecuting the idea, he found it to be the case to a very considerable extent in regard to the horizontal needle; and to take place also, though less satisfactorily, with the dipping-needle. In the former experiment a finely suspended horizontal needle was used, the directive power of which was reduced by two magnets, properly placed for the purpose; a deviation of 3° 15' was thus obtained at 11 a. m., which decreased to a late hour in the evening. The needle was kept in the same position for three days, with some change of directive power, with similar general results. After adverting to a difference in the direction of the variation in and out of doors, Mr. Barlow details the results of several experiments, which lead him to the following conclusions:—that while the north end of the needle is directed to any point from the S. to N. N. W., its motion during the forenoon advances towards the N.; and while directed towards any point between the N. and S. S. E. its motion is still to some point between the N. and N. N. W., so that there ought to be some direction between those limits in which the daily motion is a minimum: but whether this is a fixed direction during the year, or whether it has any vibratory motion as the sun changes its declination, is a question requiring further experiments to determine. Another conclusion which the author draws is, that the daily change is not produced by a general deflection of the directive power of the earth, but by an increase and decrease of attraction of some point between the N. and N. N. E., or between the S. and S. S. E.

scholarly journals On the height of the Aurora Borealis above the surface of the Earth; particularly one seen on the 29th of March, 1826

1833 ◽  
Vol 2 ◽  
pp. 342-344 ◽  
Keyword(s):  
Scientific Journals ◽  
Apparent Position ◽  
Aurora Borealis ◽  
Far North ◽  
The North ◽  
The Earth ◽  
East And West ◽  
Magnetic Meridian ◽  
North And South

The author observes that opinions differ as to the elevation of the Aurora Borealis above the surface of the earth, and that this is a point which can be determined only by a series of concurring observations. The appearance of a phenomenon of this kind on the 29th of March, 1826, assuming the form of a regular arch at right angles to the magnetic meridian, and marked by peculiar features, continuing for above an hour in the same position, afforded a most favourable opportunity for obtaining the data requisite for the solution of this problem; and the author accordingly took great pains to collect as many authentic accounts as possible of the apparent position of this luminous arch with reference to the stars, when seen from various places where it had been observed in England and in Scotland. It appears to have been actually seen in places 170 miles distant from one another, in a north and south direction, and 45 miles distant from east to west, thus comprising an area of 7000 or 8000 square miles; but it must have been visible over a much greater extent. Accounts were received of its having been seen as far north as Edinburgh, and as far south as Manchester and Doncaster, and at most of the intermediate towns; and from the exact; correspondence of the descriptions from all these places, it was impossible to doubt that they referred to the same luminous appearance. In proceeding from north to south, the apparent altitude of the arch continually increased, still keeping to the south of the zenith till we come to Kendal, at which place it very nearly crossed the zenith; at Warrington, which is further south, the culminating point of the arch was north of the zenith. Wherever seen, the arch always seemed to terminate nearly in the magnetic, east and west, at two opposite points of the horizon. The observations, in which the author places the greatest confidence for determining the height of this aurora, were those made at Whitehaven and at Warrington, places which are distant 83 miles from one another, and situated nearly on the same magnetic meridian. Calculating from the data they afford, he finds the height of the arch very nearly 100 miles above the surface of the earth, and immediately over the towns of Kendal and of Kirkby-Stephen. This conclusion is corroborated by observations at Jedburgh; but if the former be compared with those at Edinburgh, the height will come out to be 150 or 160 miles, and the position vertical about Carlisle: but he thinks the former result more entitled to confidence. Assuming the height to be 100 miles, it will follow that the breadth of the arch would be 8 or 9 miles, and its visible length in an east and west direction from any one place would be about 550 miles. The author then proceeds to take a comparative view of the results of inquiries on the height and position of other auroræ which have at different times appeared, and are recorded in the Philosophical Transactions and other scientific journals. He also gives an account of a luminous arch seen both at Kendal and at Manchester on the 27th of December last, which appeared in the zenith at the former place, and was elevated 53° from the north at the latter place; whence its height is deduced to be 100 miles. From the general agreement of this series of observations, the author infers that these luminous arches of the aurora, which are occasionally seen stretching from east to west, are all nearly of the same height; namely, about 100 miles. Observations are still wanting for the determination of the length of beams parallel to the dipping-needle, which constitute the more ordinary forms of the aurora borealis; neither can it be determined whether these beams arise above the arches, as from a base, or whether they descend below, as if appended to the arches. It is remarkable that the arches and beams are rarely, if ever, seen connected together, or in juxta-position; but always in parts of the heavens at a considerable distance from each other.

scholarly journals Interferometric Observation of the F-Corona Radial Velocities Field Between 3 and 7 R⊚

1985 ◽  
Vol 85 ◽  
pp. 77-80
Author(s):  
P.V. Shcheglov ◽  
L.I. Shestakova ◽  
A.K. Ajmanov
Keyword(s):  
Scattered Light ◽  
Interplanetary Dust ◽  
Radial Velocities ◽  
The Sun ◽  
Continuous Component ◽  
The North ◽  
The Earth ◽  
Fabry Perot ◽  
Interferometric Observation ◽  
Sky Brightness

AbstractDuring the July 31, 1981 solar eclipse, F-corona interferograms near MgI λ 5184 Å were obtained using a Fabry-Perot etalon (FPE) with an FWHM of 0.5 Å (corresponding to 30 km/sec) and an image tube. Radial velocities Vr of the interplanetary dust (i.d.) were measured in different directions.Both prograde and retrograde motions of i.d. in the ecliptic region is discovered. Most of velocity values do not exceed 50 km/sec. A negative velocity component appears after averaging all Vr for all directions. Its average increases to − 20 km/sec toward the Sun. Some ejections are observed. The strongest (+ 130 km/sec) is located at the north ecliptic pole at a distance of 6 to 7 R⊙.From the lack of unshifted Fraunhofer lines in the scattered sky light, we conclude that the sky brightness continuous component is predominant and its source is K-corona scattered light in the Earth’ s atmosphere.

scholarly journals On the diurnal variation of the magnetic declination of St. Helena

1851 ◽  
Vol 5 ◽  
pp. 664-664
Keyword(s):  
Diurnal Variation ◽  
Northern Hemisphere ◽  
Opposite Direction ◽  
Diurnal Variations ◽  
The Sun ◽  
The Earth ◽  
Magnetic Declination ◽  
St Helena ◽  
Magnetic Needle

It has long been known that the diurnal variation of the magnetic needle is in an opposite direction in the southern, to what it is in the northern hemisphere; and it was therefore proposed as a pro­blem by Arago, Humboldt and others, to determine whether there exists any intermediate line of stations on the earth where those diurnal variations disappear. The results recorded in the present paper are founded on observations made at St. Helena during the five consecutive years, from 1841 to 1845 inclusive; and also on similar observations made at Singapore, in the years 1841 and 1842; and show that at these stations, which are intermediate between the northern and southern magnetic hemispheres, the diurnal variations still take place; but those peculiar to each hemisphere prevail at opposite seasons of the year, apparently in accordance with the position of the sun with relation to the earth’s equator.

On the position of the north magnetic pole

1837 ◽  
Vol 3 ◽  
pp. 254-254 ◽  
Keyword(s):  
Vertical Position ◽  
Magnetic Pole ◽  
The North ◽  
The Earth ◽  
North Magnetic Pole ◽  
To Come ◽  
Magnetic Poles ◽  
Magnetic Needle ◽  
Made In

The author remarks that the discordances in former observations made with a view to determine the position of the magnetic pole, have arisen partly from the irregularity of distribution in the earth of the substances which exert magnetic power, and partly from the great distances from the magnetic poles at which these observations have been made. The latter cause of uncertainty has been now, in a great measure, removed, by the numerous and accurate observations made during the late arctic expeditions. The object of the present paper is to put on record those which were made in the last voyage of Captain Ross, in which a spot was reached corresponding to the true north magnetic pole on the surface of the earth. The nature of the instruments, and the difficulties encountered in their practical employment, under the circumstances of the expedition, are fully stated. Having arrived, on the 1st of June, at north latitude 70° 5' 17", and west longitude 96° 45' 48", the horizontal magnetic needle exhibited no determinate directive tendency, and the dipping needle was within a minute of the vertical position, a quantity which may be supposed to come within the limits of the errors of observation; hence the author concludes that this spot may be considered as the true magnetic pole, or as a very near approximation to it, as far, at least, as could be ascertained with the limited means of determination of which he was then in possession. A table of the observations, including those on the intensity of the magnetic force at various stations, is subjoined.

scholarly journals 3. On the Combined Motions of the Magnetic Needle, and on the Aurora Borealis.

1851 ◽  
Vol 2 ◽  
pp. 334-350
Author(s):  
J. A. Broun
Keyword(s):  
Horizontal Plane ◽  
Magnetic Force ◽  
Vertical Plane ◽  
The Other ◽  
Aurora Borealis ◽  
Centre Of Gravity ◽  
True Position ◽  
Magnetic Needle ◽  
The Way

When a steel needle or rod is so constructed that its centre of gravity is in a finely-turned axle at right angles to its length, it will rest in any position when the axle is placed upon polished planes; when, however, we magnetize the needle, it assumes a position which is that of the direction of the magnetic force at the place: in this way we obtain the ordinary dipping-needle. The dipping-needle can obviously move only in one plane, that to which the axle is at right angles; were it possible to suspend it freely, so that it could move in every plane with every variation of the direction of the magnetic force, we should then be able, by observing the variations of its position, to determine at once the laws which a magnet in its true position obeys; this, however, we have not been able to do; even the small variations in the vertical plane, which we might expect to obtain from the ordinary dipping-needle, are nearly or altogether destroyed by the friction of the axle upon its supports; and there are many mechanical difficulties in the way of the other methods of suspension. It has been found convenient, then, to make use of the simplest methods of suspending magnets in a horizontal plane; and to endeavour to deduce, from the composition of their motions, the laws both of the variation of the force with which a truly suspended magnet is directed, and of the direction of that force itself.

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