Horizontal Component Of Magnetic Field Research Articles

Redetermination of coil constant of sine galvanometer No. 1

Sine galvanometer No. 1 (SGl) was constructed by the Department of Terrestrial Magnetism, Carnegie Institution of Washington, as a primary standard for the determination of the horizontal component of the earth's magnetic field (H). The precision coil for the SGl consists of 40 turns of copper wire wound on a marble form in such a way that 20 turn-pairs can be identified which have the Helmholtz configuration with approximately 300-mm diameters and 150-mm axial spacings. The coil was first measured by Barnett [1921]. Since that time it has gained some importance as an international standard in the determination of H. Because of the importance of the SGl as an international standard, the coil constant was recently redetermined. The new results are compared with the old in Table 1.

The diurnal variation of sizes of sudden commencements and impulses in the Kodaikanal magneto grams

Combined data of sudden commencements (SCs) and sudden impulses (SIs) recorded at Kodaikanal (geomagnetic latitude 0.6°N) during the period 1949-57 have been analysed in order to study the relationship between the diurnal variation (DV) in the amplitudes of the impulses and the DV in the horizontal component of the earth's magnetic field (the sq variations in H). There is a statistically significant daytime enhancement in SC sizes similar to the enhancement in Sq variation. Furthermore, this enhancement is larger on: days with larger Sq variation than on days with smaller Sq variation. These results confirm those obtained by Forbush and Vestine (1955) at Huancayo, another station near the geomagnetic equator.

Cosmic ray intensity variations during the magnetic storm in May 1959

Cosmic ray intensity during the May 1959 magnetic storm is analysed, using neutron monitor and cubic telescope data from Mina Aguilar, Buenos Aires, Ushuaia and Ellsworth (Antarctica). The primary variation spectrum is estimated according to a method outlined in a recent paper (1). The intensity behaviour during recovery is analysed in detail. Following results are obtained. The primary variation spectrum, acting until the 18th of May, has an approximate form given byδD/D==δk(t)·E−0.5, valid up to very high energies. Around the 18th, this spectrum changes its shape at low energies (<2 GeV), in a similar way as it occured during the July 1959 storm recovery. This change may be interpreted as an additional removal of low energy particles, which lasted at least until the end of the month. On May 14, intensity variation is quite peculiar, in spite of being this a quiet day from the solar and geomagnetic point of view. A world-wide decrease occurs, with a superposed, 10 h lasting increase, which is particularly high at Ellsworth (9% in the neutron monitor, 2% for the cubical telescope). It is shown that Ellsworth was located in a 04 impact zone for a simultaneous solar event. On the 24th, a world-wide, small Forbush decrease occurred, associated with a magnetic storm and a decrease in the horizontal component of the magnetic field. This Forbush decrease, which shows a strong longitude dependence, corresponds to a primary variation spectrum which has the same shape as that responsible for the general recovery acting at the time,i.e., after the low energy change on the 18th.

Observations of unusual radiofrequency noise emission and absorption at 80 Mc/s

Unusual radiofrequency noise emissions at 80 Mc/s have been identified during periods of solar activity. The noise enhancements may be classified as (1) smooth, bay-like disturbances lasting for approximately 1 hr which occur in both day and night hours, and (2) abrupt increases, often of large but fluctuating amplitude which occur within a few hours of local midnight. The smooth enhancements occur almost simultaneously with the absorption of radiation in a sector of the northern sky. These effects could be caused by transit of high velocity streams of charged particles which produce emission from F-region levels and absorption in the E-region or below. The abrupt noise bursts at night are from the northern sky and seem to be associated with pronounced changes in the horizontal component of the earth's magnetic field. The noise may be a form of “auroral” radiation or may arise from propagation of solar noise outbursts from the sunlit to the dark hemisphere.

A new absolute instrument: the proton vector magnetometer

At the Fredericksburg Magnetic Observatory, of the Coast and Geodetic Survey, the proton-precession magnetometer has been successfully adapted, through a method conceived by the writer, for measuring the horizontal and vertical components of the earth's magnetic field. Results thus far obtained are preliminary, for there has not been sufficient time to make a series of observations for complete comparison with the existing observatory standards. The proton vector magnetometer employs the well-known proton free-precession principle for measurement of the field intensity.1,2,3 As operated at Fredericksburg, the sensing head is a bottle of water, 7 cm in diameter and 10 cm long, on which is wound a multilayer coil, serving both for polarizing the hydrogen nuclei and for picking up the precession signal. The axis is approximately horizontal and in the magnetic prime vertical. In the Z measurement, a pair of Helmholtz coils (spacing 41.3 cm) is used to nullify approximately the horizontal component of the field. The remaining (nearly vertical) component is then measured with the proton-precession magnetometer. Similarly, a second Helmholtz pair (spacing 48.6 cm) is used to nullify the vertical component, leaving only the horizontal to be measured.

Correlation of magnetic, auroral, and ionospheric variations at Saskatoon: part 2

An analysis has been made for the five-month period from December 1951 to April 1952 of the variations at Saskatoon of the horizontal component (H) of the earth's magnetic field, the position in the sky and intensity of auroral light, and of critical frequencies and heights of the ionospheric reflecting regions. There is a relationship between the maximum elevation above the northern horizon of auroral light and the maximum amplitude of variation of H. Some types of sporadic E reflecting layers appear more frequently during disturbances. Detailed analysis of magnetically disturbed nights shows that magnetic bays and certain other phenomena are correlated. An increase in the intensity of aurora is related to the rate of decrease of H in the bay. Radio wave absorption or weak reflections at levels below 100 km correspond to the periods when H is of the order of 500 gammas or more from its normal value.

Correlation of magnetic, auroral, and ionospheric variations at Saskatoon

An analysis has been made for the five-month period from December 1951 to April 1952 of the variations at Saskatoon of the horizontal component (H) of the earth's magnetic field, the position in the sky and intensity of auroral light, and of critical frequencies and heights of the ionospheric reflecting regions. There is a relationship between the maximum elevation above the northern horizon of auroral light and the maximum amplitude of variation of H. Some types of sporadic E reflecting layers appear more frequently during disturbances. Detailed analysis of magnetically disturbed nights shows that magnetic bays and certain other phenomena are correlated. An increase in the intensity of aurora is related to the rate of decrease of H in the bay. Radio wave absorption or weak reflections at levels below 100 km correspond to the periods when H is of the order of 500 gammas or more from its normal value.

An Absolute Ampere Current Balance for Laboratory Use

The ampere current balance herein described has been in use for four years as a regular experiment of a sophomore physics course. It has the following merits: (1) It is simple to construct; (2) it is absolute in that the current may be calculated from the dimensions and balancing weight only; (3) it is subject to a high degree of accuracy, especially for the larger currents; (4) it may be used for alternating as well as direct currents; (5) when current is passed through the movable conductor only, the balance may be used to measure the horizontal component of the earth's magnetic field.

An apparatus for studying the laws of the magnetic field due to an electric current in a long straight conductor

It is impracticable to measure directly the magnetic field due to an electric current in a single long straight conductor, since a complete circuit is necessary. By using a narrow rectangular coil the field is, within reasonable limits of accuracy, the same as that due to the two long sides regarded as infinite in length. The formulae for the field are simple for points along two axes relative to the coil, provided the points are not too far removed from its centre. The linearity of suitable graphs of a series of observations constitutes a verification of the law derived for a single straight conductor, and from the graphs values of the horizontal component of the earth's magnetic field can be determined. Two experimental methods, involving the location of neutral points, are described.

Gauss' method of measuring the horizontal component of the Earth's Magnetic Field, A discussion of fundamentals in the light of the actions of the International Electrotechnical Commission

This paper makes use of a discussion of Gauss' method of measuring the horizontal component of the Earth's magnetic field as a means for presenting those ideas concerning the natures of magnetic quantities which have been promulgated by the International Eleetrotechnical Commission. Reference is also made to the actions taken or initiated by the International Electrotechnical Commission (hereafter abbreviated IEC) relative to the fundamentals of measurements of mechanic, electric, and magnetic quantities.

A Sensitive Induction Magnetograph

A SENSITIVE induction magnetograph for measuring the time-rate dH/dt of the horizontal component of the earth's magnetic field is described by H. Nagaoka and T. Ikebe in Scientific Papers of the Institute of Physical and Chemical Research (Tokyo) of August 1939. The magnetograph embodies a design of a special shape for collecting the lines of force into a permalloy core enclosed in a cylindrical coil. A record is given of complicated magnetic disturbances caused by electric trams. Even at a distance of several hundred kilometres from a great city, the disturbances can be detected as minute ripples on the traces. The selection of an observing station for observing true geophysical phenomena is therefore a difficult problem. The observed effect of weak earthquake shocks is discussed. Apart from the purely mechanical effects of shock, there are probably some true magnetic effects due to the varying magnetic susceptibility of erupting lava (the subject of study being the Asawa volcano). The authors think that it may be possible to predict violent eruptions half an hour before they occur. It is also anticipated that the new magnetograph will provide data to test whether short-period disturbances of a few seconds’ duration exist during magnetic storms. Provided that a suitable site can be obtained, the magnetograph has other applications in the study of the characteristics of the E- and F-layers of the ionosphere with respect to the height of origin of the current system producing the diurnal variation of the earth's magnetic field.

Points from Foregoing Letters

COMPARISON of the change in the intensity of cosmic rays for a period of nine days (April 23-May 1, 1937) during a magnetic storm at Innsbruck (Austria), Cheltenham (Maryland, U.S.A.) and Huancayo (Peru), shows very good agreement in the general trend, according to Prof. V. F. Hess and A. Demmelmair. There is also a close parallelism to the change in the horizontal component of the earth's magnetic field during this period, and the authors conclude that cosmic ray ionization was influenced simultaneously all over the earth by the magnetic disturbances, and that the study of the magnetic storm effects will give valuable information on the distribution of energy in the spectrum of the cosmic radiation.

The apparent effect of magnetic activity upon the secular variation of the Earth's magnetic field

That the horizontal component of the Earth's magnetic field undergoes a variation which is associated with the sunspot‐cycle has been noted by numerous investigators. Particularly noteworthy is the monumental work of Moos (Magnetic observations made at the Government Observatory, Bombay, 1846–1905, Part 2, 265, 1910) in which the data from Bombay are discussed. Fisk (Proc. Fourth Pacific Sci. Cong., Java, 1929, v. 2, 517–534, 1930) has also investigated the problem in another way.

On the determination of the horizontal component of the earth's magnetic field by a coupled oscillations method

An account is given of a simple experiment designed to illustrate quantitatively the phenomena of coupled oscillations. Two similar small magnets are suspended in the earth's magnetic field at a suitable distance apart so that there is appreciable magnetic interaction between the two oscillatory systems. Under the conditions employed, the equations of motion reduce to a simple form, and the experiment may be used as a method of measuring the intensity of the horizontal component of the earth's magnetic field.

A simple apparatus for the measurement of the horizontal component of the Earth's magnetic field

A simple piece of apparatus for the determination of H is described. It is based on the method used by Schuster and F. E. Smith. In the form described it is intended mainly for use in teaching laboratories.

Tentative magnetic values as recorded at the Apia Observatory for the year 1927

Continuous records of the declination and of the horizontal component of the Earth's magnetic field were obtained during 1927 at Apia Observatory, latitude 13°48′ south, longitude 171°48′ west. Owing to the length of time which must necessarily elapse before publication of the hourly values of these elements, it is considered desirable to announce tentative values which, although subject to revision, will probably remain unchanged. These data, as given in the following table, are based on the means of all the hourly values during the month giving the so‐called “all‐days value” for the magnetic element concerned:

A differential method for deriving magnetometer deflection‐constants

For the computation of the horizontal component of the Earth's magnetic field from the observed angle of deflection of one magnet by a second in Lamont's first position a factor, intrinsically a function of the dimensions of the magnets employed, is required to correct for these finite dimensions. The so‐called “distribution‐coefficients” concerned in this factor are generally determined by means of a rather tedious computation depending on the data observed at three deflection‐distances. Theoretically the ratio of the sines (or the difference of the logarithmic sines) of the observed angles of deflection for any two distances is constant for a given instrument and pair of magnets; differential methods based on this theoretical condition are developed which simplify the computations required.The more exact form of the distribution‐factor, (1+Pr−2+Qr−4), is found to be less satisfactory in practice than the simpler form (1+P′r−2) for magnets which have been designed to make the value Q as small as possible (theoretically zero), on account of the greater sensitiveness to changes in the sine‐ratios of the factor containing both P and Q. The paper includes numerical examples and tabulations to show the application of the derived formulas to the determination of distribution‐coefficients, constants, and corrections on standard for a number of magnetic instruments of the Carnegie Institution of Washington.

Results from magnetic east‐west paths around the Earth

In the preliminary analysis of the Earth's magnetic field for 1922 by Dr. Louis A. Bauer,1 it was found desirable to ascertain how an east‐west path around the Earth would close that was everywhere throughout its length perpendicular to the direction of the compass needle, or to the horizontal component of the Earth's magnetic field. The considerations involved and the method adopted in constructing eleven such paths are given in these notes, together with the results.The actual tracing of a path with the required accuracy, exactly magnetic east or exactly magnetic west, on land and over sea, presents many practical difficulties. Periodical time changes all along the path introduce uncertainties. Over land, local disturbances2 interfere and cities and other constructional culture obstruct the necessary surveying operations, while over the seas, where the only available method at present is to continue the path on a non‐magnetic ship, ocean currents and leeway affect the closure sought, not only by precisely the sum of their components perpendicular to the path, but also by shifting the path in regions of critical or steep gradients of the declination, and thereby introducing errors in its direction. The tracing of a path upon isogonic charts of the world is free from these sources of error though subject to others. Local disturbances have been effaced in the smooth isogonics, and time changes are taken care of in the reduction to a common epoch. Cultural detail, ocean currents and winds no longer enter the problem. Hence the plotted closure of a circuit extending exactly magnetic east or west around the Earth depends in this method only upon the systems of magnetization represented by the particular isogonics and upon the accuracy with which data can be scaled from the chart or plotted thereon. Unfortunately, the errors of plotting usually accumulate. It is possible to compute the closure of the path by a long process involving repeated approximations, provided that the magnetic declination is given as an analytical function of the latitude and longitude. The work entailed, however, renders this method practically useless.

The electrochemical equivalent of silver

A preliminary account of the recent redetermination of the electrochemical equivalent of silver by Van Dijk and Kunst has been given in the “Proc. Roy. Acad., Amsterdam, Jan. 21, 1904,” and in the “Ann. Phys. Vol. 14, p. 569, 1904.” Van Dijk has now published the interesting details of the research.The tangent galvanometer method was employed, a method which requires the accurate knowledge of the intensity of the horizontal component of the Earth's magnetic field. This was determined by means of a bifilar magnetometer, with wires 232 cms. long and 12.4 cms. apart. Great pains were taken to eliminate all possible errors, and the difficulties encountered clue to local magnetic influences in the instruments are fully described.

LIX. On measurements of the intensity of the horizontal component of the earth's magnetic field made in the physical laboratory of the University of Glasgow

(1885). LIX. On measurements of the intensity of the horizontal component of the earth's magnetic field made in the physical laboratory of the University of Glasgow. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science: Vol. 20, No. 127, pp. 484-497.