IV. Comparison of simultaneous magnetic disturbances at several observatories

In my former on Magnetic Disturbances and Earth Currents, which were read at the ngs of the British Association at Swansea in 1880 and at York in 1881, a iparison was made of the declination and the horizontal force traces given by the self-recording instruments at five European stations, also at one station in India, one in China, and one in Australia. An attempt was made to determine the relative amounts of the simultaneous changes at the several observatories by comparing them with one another by means of the scale values of the instruments employed, which were all of the pattern of the self-recording instruments at the Kew Observatory. It was found on comparison that there were great differences in the scale values of the instruments of the same kind at the different observatories, and in some ca here was great uncertainty as to the scale values, because no determination of had recently been made. Hence great difficulty was found in arriving at the meaning of the records which were taken regularly at the different observatories. The comparison was sufficient to show the great importance of adopting the same scale values for the like instruments at all observatories. In my paper a recomendation was made that for horizontal force records a scale value of ·0005 millimetremilligramme for a difference of scale reading of 1 mm. should be adopted as being the most convenient. The same scale value was recommended by Dr. Wild, of the St. Petersburg Observatory, and for the vertical force magnetometer the same scale value might conveniently be adopted. With this scale value the instruments would be sufficiently sensitive to give for a considerable magnetic disturbance changes which are capable of being measured, but yet would not be so sensitive as to send the spot of light off the photographic paper, even in a violent magnetic storm.

I. Note on an extension of the comparison of magnetic disturbances with magnetic effects inferred from observed terrestrial galvanic currents; and discussion of the magnetic effects inferred from galvanic currents on days of tranquil magnetism

10.1098/rspl.1869.0045 ◽

1870 ◽

Vol 18 (114-122) ◽

pp. 183-185

Keyword(s):

Magnetic Force ◽

The Self ◽

Instrumental Error ◽

Magnetic Disturbance ◽

Magnetic Effects ◽

Royal Observatory ◽

Moderate Disturbance ◽

Magnetic Disturbances ◽

Made In

The author, after referring to his paper in the Philosophical Transactions for 1868 on the comparison of Magnetic Disturbances inferred from Galvanic Currents recorded by the Self-registering Galvanometers of the Royal Observatory of Greenwich with the Magnetic Disturbances registered by the Magnetometers, on 17 days, states that he had now undertaken the examination of the whole of the Galvanic Currents recorded during the establishment of the Croydon and Dartford wires (from 1865 April 1 to 1867 October 24). The days of observation were divided into three groups,—No. I containing days of considerable magnetic disturbance, and therein including not only the 17 days above mentioned, but also 36 additional days, No. 2 containing days of moderate disturbance, of which no further use was made, and No. 3 containing the days of tranquil magnetism. The comparisons of the additional 36 disturbed days were made in the same manner as those of the preceding 17 days, and the inferences were the same. The results were shown in the same manner, by comparison of curves, which were exhibited to the Society. The points most worthy of notice are, that the general agreement of the strong irregularities, Galvanic and Magnetic, is very close, that the galvanic irregularities usually precede the magnetic, in time, and that the northerly magnetic force appears to be increased. The author remarks that no records appeared open to doubt as regards instrumental error, except those of western declination; and to remove this he had compared the Greenwich Curves with the Kew Curves, and had found them absolutely identical.

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

Some phenomena of magnetic disturbances at Kew

10.1098/rspa.1910.0049 ◽

1910 ◽

Vol 83 (566) ◽

pp. 579-581

Keyword(s):

The Other ◽

Diurnal Changes ◽

Vertical Force ◽

Horizontal Force ◽

Rapid Rise ◽

Sunspot Maximum ◽

Magnetic Elements ◽

Early Afternoon ◽

Phase Angles ◽

A recent paper discussed the diurnal inequality of Kew magnetic declination derived from 209 of the most highly disturbed days of the eleven years 1890 to 1900. The present paper discusses the corresponding phenomena for the same days in the other magnetic elements. The most prominent features of disturbed days are the irregular nature of magnetic changes, and the frequency of large oscillations. These more obvious features have hitherto engrossed attention. It is found, however, that the irregular changes on disturbed days are accompanied by large regular diurnal changes, which are specially striking in vertical force. In declination and horizontal force the range of the regular diurnal inequality on disturbed days is in the average month of the year about double that on quiet days, but in vertical force the former range is fully four times the latter. Disturbance affects the type as well as the range of the diurnal inequality. The former influence is comparatively small in horizontal force and the component to geographical north, larger in declination and the component to geographical west, and largest of all in vertical force. On quiet days the characteristic feature of the vertical force inequality is the fall in the forenoon to the minimum about 11 a. m. and the rapid rise in the early afternoon. Disturbed days, however, approach to a type in which there is a minimum about 4 a. m.— near the principal barometric minimum for the day—and a maximum at from 4 to 6 p. m. according to the season. The day rise and the night fall are about equally rapid. On disturbed days the shorter period Fourier “waves” in the diurnal inequality for V become of reduced importance relative to the 24-hour wave, and this wave has its phase some four hours earlier than on quiet days. Vertical force inequalities from the disturbed days of the four sunspot maximum years 1892—1895 show a considerably larger range than those from the whole 209 days, and their phase angles depart more from the phase angles for the quiet days of the eleven years.

Philosophical Transactions of the Royal Society of London. Series A, Containing Papers of a Mathematical or Physical Character ◽

VIII. Some phenomena of magnetic disturbances at Kew

10.1098/rsta.1911.0008 ◽

1911 ◽

Vol 210 (459-470) ◽

pp. 271-306

Keyword(s):

National Physical Laboratory ◽

Vertical Force ◽

Horizontal Force ◽

Physical Laboratory ◽

Magnetic Disturbances ◽

Frequent Reference

1. In the course of the present paper frequent reference is required to two previous papers, termed for brevity (A) and (C), which dealt with results derived from the Kew magnetograms of the eleven years 1890 to 1900. (A) dealt with results from the Astronomer Royal’s “quiet” days only, but included Declination, Inclination, Horizontal Force, and Vertical Force—termed sometimes for brevity D, I, H, and V. (C) dealt with declination only, but included results from all ordinary days and from the more highly disturbed days treated separately. Some results which had to be omitted from (C), or which are only glanced at there, were discussed in an appendix—termed here (C')—attached to the reprint of (C) in Vol. V. of the ‘Collected Researches’ of the National Physical Laboratory.

XI. Note on an extension of the comparison of magnetic disturbances with magnetic effects inferred from observed terrestrial galvanic currents; and discussion of the magnetic effects inferred from galvanic currents on days of tranquil magnetism

Philosophical Transactions of the Royal Society of London ◽

10.1098/rstl.1870.0011 ◽

1870 ◽

Vol 160 ◽

pp. 215-226 ◽

Cited By ~ 2

Keyword(s):

Royal Society ◽

Principal Part ◽

The Self ◽

Magnetic Disturbance ◽

Magnetic Effects ◽

The Earth ◽

Royal Observatory ◽

In a communication to the Royal Society, which was honoured by publication in the Philosophical Transactions for 1868, I described the methods and gave the results of comparing the Magnetic Disturbances which might be expected as consequent on the Terrestrial Galvanic Currents recorded by the self-registering galvanometers of the Royal Observatory of Greenwich, with the Magnetic Disturbances actually registered by the self-registering magnetometers. The comparison was limited to seventeen days (1865, October 5 and 31; 1866, October 4; 1867, April 4, 5, 7, 8, 9, 11, May 4, 14, 28, 31, June 1, 2, 7, 24), various days having been omitted in consequence of a doubt on the uniformity of the clock-movement of the registering-barrel, which afterwards proved to be unfounded. The results of the comparison were exhibited in curves, engraved copies of which are given in the volume of publication. I expressed my opinion that it was impossible to doubt the general causal connexion of the Galvanic Currents with the Magnetic Disturbances, but that some points yet remained to be cleared up. As soon as circumstances permitted, I undertook the examination of the whole of the Earth-currents recorded during the establishment of the Croydon and Dartford Wires (namely from 1865 April 1 to 1867 December 31), as far as they should appear to bear upon this and similar questions. For this purpose the days of observation were divided by Mr. Glaisher into three groups. Group No. 1 contained days of considerable magnetic disturbance (or days of considerable galvanic disturbance, which are always the same), including, besides the seventeen days above-mentioned, the thirty-six days of the following list :—1865, April 15, 16, 17, 18, 19, May 14, 17, July 7,15, August 14,19, 26, September 8, 16, 28, October 4, 6, 10, 12, 14, November 1; 1866, August 11, 23, September 8, 9,12,13,17,18, 25, October 6, 7,10, 30, November 26 ; 1867, February 8; making in all fifty-three days of considerable magnetic disturbance. Group No. 2 consisted of days of moderate magnetic disturbance, and of these no further notice was taken. Group No. 3 contained the days of tranquil magnetism, and the discussion of these will form the principal part of the present Memoir.

II . Results of the monthly observations of magnetic dip, horizontal force, and declination made at the Kew Observatory from April 1869 to March 1875 inclusive

10.1098/rspl.1875.0028 ◽

1876 ◽

Vol 24 (164-170) ◽

pp. 232-240

Keyword(s):

Royal Society ◽

Horizontal Force ◽

Absolute Determination ◽

The Third ◽

The Absolute ◽

This paper, containing the result of six years’ magnetic observations at the Kew Observatory, follows as the third of a series of publications, the first of which was a communication to the Royal Society by General Sir E. Sabine, published in the Philosophical Transactions for 1863, page 273, which consisted of a discussion of certain selected magnetic disturbances, a general discussion of declinational changes as recorded by the magnetographs, and a discussion of the absolute determination of Dip and Horizontal Force at the Observatory, for the six years April 1857 to March 1863 inclusive.

VI. Comparison of simultaneous magnetic disturbances at several observatories, and determination of the value of the Gaussian functions for those observatories

10.1098/rspl.1891.0017 ◽

1892 ◽

Vol 50 (302-307) ◽

pp. 129-130

Keyword(s):

Magnetic Storm ◽

Gaussian Functions ◽

Magnetic Disturbances ◽

Photographic Records

After drawing attention to previous investigations on this subject, and pointing out the importance of adopting the same scale values for similar instruments at different Observatories, especially at new Observatories which have been recently established, the discussion of special magnetic disturbances is undertaken, especially the disturbances of a great magnetic storm which occurred on June 24 and 25, 1885, for which photographic records have been obtained from 17 different Observatories: 11 in Europe, 1 in Canada, 1 in India, 1 in China, 1 in Java, 1 at Mauritius, and 1 at Melbourne.

XI. Records of the magnetic phenomena at the Kew observatory.—No. IV. Analysis of the principal disturbances shown by the horizontal and vertical force magnetometers of the Kew Observatory, from 1859 to 1864

Philosophical Transactions of the Royal Society of London ◽

10.1098/rstl.1871.0012 ◽

1871 ◽

Vol 161 ◽

pp. 307-319

Keyword(s):

The Self ◽

Vertical Force ◽

Horizontal Force ◽

Good Preservation ◽

Magnetic Elements ◽

Magnetic Observatories ◽

Magnetic Phenomena

This paper contains an analysis of the first portion of the Automatic Records obtained at the Kew Observatory by means of the self-recording Horizontal and Vertical Force Magnetometers devised by the late Superintendent of that Observatory, Mr. John Welsh, aided by Mr. Beckley, Engineer in that establishment. The Record of the Horizontal Force commenced on the 1st of January, 1858, and that of the Vertical Force a year later, viz. on the 1st of January, 1859. The present notice includes the records of both to the 31st of December, 1864,—making seven complete years of the Horizontal Force, and six complete years of the Vertical Force. The daily Photograms, from which the results have been derived, are carefully preserved at the Observatory, and hitherto, at least, appear to have suffered little or no deterioration. The apparatus and methods by which the photograms are obtained have been already fully described. The Observatory had the great misfortune of losing the Superintendence of Mr. Welsh by his decease in 1859; but the instruments and methods which he had so ably devised, have continued and still continue in use, unchanged. It was originally his intention to discuss the results obtained with the self-recording magnetic instruments in successive periods, each of six years, beginning with 1858 ; but in consequence of the illness which preceded his death, no preparations had been made for the commencement of this work. The photograms were indeed preserved with all suitable care, but were liable, as must necessarily be the case even under the most favourable conditions, to deterioration. Under these circumstances I ventured in 1862 to propose to Mr. Gassiot, Chairman of the Kew Committee (of which I was myself a member), that the photograms of the First of the Periods contemplated by Mr. Welsh, viz. from January 1, 1858, to December 31, 1864, should be entrusted to me, to be tabulated by the non-commissioned Officers at the Woolwich Magnetic Office, and subsequently discussed by myself on the same plan as the Eye-observations at the Colonial Magnetic Observatories had been discussed. This arrangement, so far as the tabulation was concerned, was speedily effected, and the Photograms were forthwith returned for safe custody to Kew, where they remain and are in good preservation. My own time, and that of the Office, having been much occupied latterly in preparing the Maps of the Magnetic Elements corresponding to the Epoch of 1842.5, the deductions from the Photograms, from January 1858 to December 1864, have not been completed at so early a date as I could have wished, and should otherwise have accomplished; but I now present them as the first instalment of a research which I hope we may regard as permanently established and provided for by Mr. Gassiot’s munificent donation.

On the simultaneity of magnetic variations at different places on occasions of magnetic disturbance, and on the relation between magnetic and earth current phenomena

10.1098/rspl.1892.0068 ◽

1893 ◽

Vol 52 (315-320) ◽

pp. 191-212 ◽

Cited By ~ 6

Keyword(s):

Magnetic Observatory ◽

Vertical Force ◽

Horizontal Force ◽

Magnetic Disturbance ◽

Magnetic Declination ◽

Made In

The observations made in a magnetic observatory usually include absolute measures of magnetic declination, horizontal force, and dip (inclination); with photographic registration of the variations of declination, horizontal force, and vertical force ; to which is added, at Greenwich, a photographic registration of earth currents.

I. On the luni-solar variations of magnetic declination and horizontal force at Bombay, and of declination at Trevandrum

Philosophical Transactions of the Royal Society of London. (A.) ◽

10.1098/rsta.1887.0001 ◽

1887 ◽

Vol 178 ◽

pp. 1-43 ◽

Cited By ~ 7

Keyword(s):

Diurnal Variation ◽

Whole Body ◽

Horizontal Force ◽

Magnetic Disturbance ◽

The Moon ◽

Tropical Regions ◽

Meteorological Observations ◽

Tropical Station ◽

Small Disturbances

In the early attempts to investigate the influence of the moon upon terrestrial magnetism, the observations dealt with extended over periods so limited that little was possible beyond determining the average character of the lunar diurnal variation. This was mainly because magnetic disturbance tends—and especially in extra-tropical regions—to mask the minute variations that depend upon the moon. The series of observations made at the Coldba Observatory, Bombay, and discussed in the present paper, extending over twenty-five years in the case of the declination and over twenty-six and a half years in the case of the horizontal force, possesses therefore the double advantage of being originally affected by only the relatively small disturbances of a tropical station, and of being lengthy enough to secure an approximate elimination of such disturbance as is involved in it, even by combination of portions only of the whole body of observations. 2. The instruments used at Colába were made by Grubb, of Dublin, and are like those described in the report (of 1840) of the Committee of Physics of the Koyal Society, the magnets being fifteen inches long. An account of them and of their history will be found in the * Appendices to the Bombay Magnetical and Meteorological Observations, 1879 to 1882 / pages [84] and [138]: and to this account reference may be made for particulars as to the adjustments and determination of scale coefficients of both the declination and horizontal force magnetometers, and as to the determination of the temperature coefficient of the latter instrument. The following extract is, however, given in full, the matter of it being essential to an understanding of the principal object of this paper.

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

The magnetic storm of December 16-17, 1917, as recorded at Kew and Eskdalemuir observatories

10.1098/rspa.1918.0038 ◽

1918 ◽

Vol 94 (664) ◽

pp. 525-547

Keyword(s):

Magnetic Storm ◽

Turning Point ◽

Vertical Force ◽

Horizontal Force ◽

Electrical Currents ◽

The North ◽

Short Period ◽

Period Oscillation ◽

Original Direction ◽

The Times

1. In a recent paper, I described a magnetic storm occurring on August 22, 1916, in which the disturbances recorded at Kew and Eskdalemuir Observatories were closely similar in type. The magnetic storm on December 16-17, 1917, affords in many ways a remarkable contrast, the changes recorded at the two observatories differing notably in type. The disturbance was the largest of the year. In the Kew declination (D) and horizontal force (H) curves, a prominent feature was a succession of oscillations with periods of about 20 minutes, and it was the hope of identifying these with corresponding oscillations at Eskdalemuir that suggested the present investigation. Dr. Crichton Mitchell, the Superintendent of Eskdalemuir Observatory, kindly sent the original curves, so the comparison was made under favourable conditions. One of the obstacles to the identification of corresponding movements at the two stations is that, while H and D are recorded at Kew, the north (N) and west (W) components are recorded at Eskdalemuir. On instituting a minute comparison between the Kew H and D curves, it was found that, while oscillations with periods not far from 20 minutes were prominent in both, the times of the turning points by no means always agreed. A turning point in the H curve, for instance, might be represented by a short arrest or slight temporary reversal of movement in the D curve, the original direction of the D movement being almost immediately resumed. Again, towards the end of an oscillation, the trace might be nearly level for some minutes, or there might be a small short period oscillation, so that more than one choice was possible when assigning a time for the end of one major oscillation or the beginning of the next. Thus, when one had to compare Kew H with Eskdalemuir N curves, and Kew D with Eskdalemuir W curves, the fact that corresponding movements were difficult to identify is not surprising. Both observatories record vertical force (V), but the Kew V curves are so much disturbed by artificial electrical currents that they cannot be relied on for minor details. There were also difficulties special to the particular storm. Some of the N and W movements at Eskdalemuir were so rapid that the photographic trace was in places almost invisible. While the time marks occur on the base lines as well as on the curve lines, there is sensible parallax, and when the marks on the curve lines become invisible, the time cannot be fixed with quite the usual accuracy.