bluuebunny/crossref_metadata_2025 huggingface dataset:
Watheroo Magnetic Observatory January to March, 1936
Authors: Green J. W.
Published: February 2008

(Latitude 30° 19′.1 S., longitude 115° 52′.6 or 7h43m.5 E. of Gr.)

There were no magnetic disturbances of any intensity during the quarter. Three sudden commencements of moderate intensity were observed. The sudden commencement of February 14 began at 17h 23m, G.M.T., when the horizontal intensity increased 13 gammas in two minutes. On February 16 another sudden commencement took place at 18h 57m when the horizontal intensity increased 36 gammas in three minutes. A further one occurred on March 20 when the vertical‐intensity inductometer recorded the beginning at 2h 52m 44s; the increase in horizontal intensity was only 8 gammas in the comparatively long period of eight minutes.
On the effective group‐velocities of low‐frequency radio time‐signals and the apparent variability of velocity with the region of the Earth traversed
Authors: Stetson Harlan True
Published: February 2008

In a preliminary report to the American Geophysical Union at the Washington meeting in 1934, attention was called to apparent variations in the velocity of propagation of the low‐frequency radio waves used in the international comparisons of time‐signals1. The suggestion was therein made that the velocities over different paths were in some way inversely related to the distance of the path from the Earth's magnetic pole.

Investigations have since been extended to include additional data. Unfortunately, on account of changes in the transmitting equipment at the Naval Station at Annapolis, the two‐way communication of time‐signals between Washington and Greenwich and likewise between Washington and Paris was interrupted in 1934 so that current data are lacking until such a time as the exchange of signals shall be reestablished on the 17‐kilocycle frequency.
A comparison between absolute and variometric magnetic measurements
Authors: Koenigsberger J. G.
Published: February 2008

The accuracy of variometric magnetic measurements is not often checked as such observations of different decades are not comparable. The question arises—similarly as now found by comparison of observations with the pendulum and gravity‐variometer—if the magnetic variometer may give also for greater distances results of the same accuracy as absolute methods.

There is an opportunity for such a comparison in Switzerland. For 1931.5 W. Brückmann1 has made absolute measurements, designated as 1, below, of the magnetic elements, his results being published late in 1932, and for 1930.5 the author has measured the horizontal and vertical components H and Z with a variometer, designated as 2, below, on a profile 200 km long through the same country from Chiasso to Basel, published early in 19322.
Secular change at Tsingtao since 1924
Authors: Liu Chao‐Yang
Published: February 2008

The department of terrestrial magnetism of Tsingtao Observatory was founded some time before the World War, but the records available for the Chinese administration can be traced back only to the year 1924. The magnetograph in use is of Eschenhagen type; it consists of a recording apparatus and a declination‐variometer by Toepfer, a horizontal‐intensity variometer by Carpintur, and a vertical‐intensity variometer by Schulze. The instruments for absolute observations are a magnetometer for both declination and horizontal intensity by Sartorius and a Wild earth‐inductor by Schulze and galvanometer for inclination.

So far as the short period from 1924 to 1935 is concerned, the diurnal variations here of the magnetic elements have been found to be not very great. Thus for declination, the absolute differences between the mean values of two successive months never reached 10′, for vertical intensity—except for a few doubtful cases—seldom exceeded 100γ, and for horizontal intensity—the most active and at the same time seemingly also the most sensitive one of the three records—none ever exceeded 100γ.
A soalr eruption of November 27, 1936, and simultaneous disturbances in Earth's magnetism, earth‐currents, and the ionospheric regions
Authors: Davies F. T. , Torreson O. W. , Scott W. E. , Stanton H. E.
Published: February 2008

Spectrohelioscope‐observations—From 16h 50m to 16h 58m GMT on November 27, 1936, an extremely bright circular flocculus was observed. Its approximate position was 6° South and 21° East.

Magnetic record—A sudden commencement occurred in all three elements at 16h 50mGMT, terminating at 17h 00m after very small changes. These changes would hardly be worthy of note but for their simultaneity with a solar eruption.
Tucson Magnetic Observatory October to December, 1936
Authors: Joyce J. Wallace
Published: February 2008

(Latitude 32° 14′.8 N., longitude 110° 50′.1 or 7h 23m.3 W. of Gr.)

October 16–17—A disturbance of moderate intensity was characterized by abrupt starts in D and H at 15h 01m GMT, October 16. The storm, which consisted of several large bays with superimposed short‐period activity in D and H, ended at about 14h, October 17. Ranges were: H, 126 gammas; Z, 51 gammas; D, 15′.
Cheltenham Magnetic Observatory April to June, 1937
Authors: Ludy Albert K.
Published: February 2008

(Latitude 38° 44′.0 N., longitude 76° 50′.5 or 5h 07m.4 W. of Gr.)

April 24–28—A magnetic storm of great severity was in progress from noon of April 24 to midnight of April 28. The storm was not continuously severe during the full period but had the appearance of four storms with lulls between them. The range of declination for the whole storm was 72′; of vertical intensity 866 gammas; and the estimated range of horizontal intensity was 735 gammas. The storm began with moderate activity but at 19h GMT, April 24, it increased in violence and was very active until 02h, April 25, when it moderated. This period of the storm was characterized by a very high value of vertical intensity at 23h 45m when it reached a value about 425 gammas above normal. The ranges for the period were: D, 36′; H, 223 gammas; and Z, 485 gammas. After a time of comparative quiet the storm was again active from 15h 48m, April 25, to 7h, April 26. Between 19h and 23h, April 25, all three elements were very active with short‐period perturbations of moderate ranges in D and Z but large range in H. This part of the storm was characterized by high values and great range in H. The H‐trace went completely off the magnetogram, indicating a range of more than 400 gammas. The ranges in D and Z during this time were 36′ and 106 gammas respectively. The elements were again fairly quiet until 17h 40m, April 26, when the storm once more became violent for a period of 11 hours. This period was notable for the high values in both H and Z; the H‐trace again left the magnetogram. The ranges were: D, 48′; H, more than 400 gammas; and Z, 382 gammas. Another period of quiet occurred until 18h 40m, April 27. Then the storm again became violent and was characterized by low values of H and Z and a large range in D. The ranges were: D, 72′; H, 455 gammas; and Z, 523 gammas. The storm ended at midnight, April 28.
Über die Methode von Arthur Schuster zur analytischen Darstellung numerisch gegebener Funktionen auf der Kugelfläche
Authors: Schmidt Von Adolf
Published: February 2008

A. Schuster's method for calculating the coefficients in the development of a given function into a series of spherical harmonics reduces the computation to ordinary harmonic analysis; the sine and cosine terms with the multiples of the co‐latitude as arguments are, once for all, developed into spherical harmonics. For this development, two possibilities offer themselves, the one leading to finite series, the other, chosen by Schuster, leading to infinite series. The reasons for this choice are discussed. Certain objections to the method are found justified, namely, that its application should be restricted to cases in which the given function is known with equal accuracy all over the surface of the globe instead of being represented—as in most geophysical applications —by insufficient data in the polar areas or in the Southern Hemisphere. Formulae for practical calculations and an extract from Schuster's tables, for use with normalized harmonics, are given.
Remarks on S. Chapman's note on radio fade‐outs and the associated magnetic disturbances
Authors: Kirby S. S.
Published: February 2008

In Dr. Dellinger's absence from the United States I thank Professor Chapman for pointing out Birkeland's important, and partially neglected, contributions to the knowledge of the perturbations of the Earth's magnetic field. During the past two and one‐half years ionospheric research by radio methods has contributed to the elucidation of the phenomena of solar and terrestrial physics with striking rapidity. A brief review of the recent impressive contributions of ionospheric research to these problems appears to be in order along with Chapman's review of Birkeland's work, and will show the fruitfulness of the radio methods. Dellinger announced the radio fade‐out as a semi‐world‐wide phenomenon, occurring on the illuminated hemisphere of the Earth, depending on some solar emanation lasting only a few minutes and with an apparent 54‐day recurrence period.
Watheroo Magnetic Observatory July to September, 1937
Authors: Green J. W.
Published: February 2008

(Latitude 30° 19′.1 S., longitude 115° 52′.6 or 7h 43m.5 E. of Gr.)

July 19—There was a sudden commencement on July 19 at 12h 53m 50s GMT. D moved easterly 1′ and returned to normal in two minutes of time. Then after an interval of twelve minutes a slow westerly movement began, the total change being 4′ in the following fourteen minutes. H increased 27 gammas in four minutes, then remained high and undisturbed. The numerical value of Z abruptly decreased 6 gammas, then increased 4 gammas, followed by a slow decrease of 15 gammas over twelve minutes and an increase of 20 gammas over fifteen minutes. The character of the trace was “1” for several hours.
Nachtrag zu dem Aufsatze “Über die Methode von Arthur Schuster zur analytischen Darstellung numerisch gegebener Funktionen auf der Kugelfläche”
Authors: Schmidt Von Adolf
Published: February 2008

Die Zusammenstellung der gebrauchsfertigen Formeln für die Koeffizienten gnσ und hnσ, die am Schlusse folgen sollte, fehlt dort. Für die zonalen Funktionen (σ = 0) stehen die betreffenden Formeln auf S. 350, für die übrigen werden sie hier nachträglich mitgeteilt. Die Zahlenwerte der Faktoren der aP und bp (bzw αp und βp) findet man übrigens, und zwar auf 5 Dezimalen angegeben, in der Tabelle auf S. 353. Der hier versehentlich benutzte Index m ist mit σ gleichbedeutend.
Temperature‐compensation of the unifilar by means of Thermalloy
Authors: Janowsky B. M.
Published: February 2008

(1) Theoretical considerations—The equation of equilibrium of an unifilar, that is, of a magnet suspended by an elastic fiber and being under the action of the horizontal component H of the magnetic field of the Earth has the form

urn:x-wiley:00968013:media:tma32249:tma32249-math-0001
where M is the magnetic moment of the magnet, θ is the angle between the magnetic axis of the magnet and the magnetic meridian, ϕ is the angle of torsion of the suspension‐fiber and C is the coefficient of torsion of the fiber.
Note on effect of torsion in QHM observations
Authors: Howe H. Herbert
Published: February 2008

Using approximations to the trigonometric functions involved, a simple expression is obtained for the error resulting from imperfect elimination of initial torsion in the fiber.
Provisional sunspot‐numbers for February to April 1938
Authors: Brunner W.
Published: February 2008

(Dependent alone on observation at Zürich Observatory and its station at Arosa)
Magnetic Observatory, Capetown, October 1937 to March, 1938
Authors: Ogg A.
Published: February 2008

(Latitude 33° 57′ S., longitude 18° 28′ or 1h 13m.9 E. of Gr.)

Note: The absolute values of D and Z are negative and that of H is positive; the changes indicated by sign are in the algebraic sense.
Geomagnetism or terrestrial magnetism?
Authors: Chapman S.
Published: February 2008

The purpose of this Note is to suggest to workers on the science of the Earth's magnetism, who write in English, that they should regularly adopt the title geomagnetism, and the corresponding adjective geomagnetic, in place of the more usual terrestrial magnetism and terrestrial magnetic. The adjective geomagnetic is already commonly used in connection with the angular coordinates of position on the globe, relative to the Earth's magnetic axis; but in other connections, at present, it occurs seldom.

I am not enough of a historian to know when the title terrestrial magnetism became general, or why it ever gained vogue, when the old words geography and geology already offered analogies for the word geomagnetism. But apart from the stylistic literary objection to the combination of a Latin adjective terrestrial with a noun originally Greek —an argument which to many scientists may not have much appeal —the use of the Greek earth‐prefix geo with the main noun magnetism, in line with the nomenclature for geography, geodesy, geophysics and geology, has the great advantage of convenience, brevity, and ease of speech. The adjectival form of the word, geomagnetic, has a still greater convenience over the awkward adjectival phrase terrestrial magnetic, in which the second adjective is qualified by the separate subadjective terrestrial.
Huancayo Magnetic Observatory, April to June 1938
Authors: Davies Frank T.
Published: February 2008

(Latitude 12° 02′.7 S., longitude 75° 20′.4 or 5h 01m.4 W. of Gr.)

April 6—A sudden commencement of small amplitude occurred at 21h 05m GMT, April 6. In a period of four minutes, H decreased 5 gammas and increased 42 gammas; Z increased 5 gammas and D moved westward less than 1′.0. Following this the traces were only slightly disturbed.
American URSI broadcasts of cosmic data, July to September, 1938, with american magnetic character‐figure CA, August to October, 1938
Authors: Johnston H. F.
Published: February 2008

The data for terrestrial magnetism, sunspots, and solar constant are the same as given in previous tables.

The first three columns of the Table give (1) the magnetic character according to the scale 0–2 of the International Commission of Terrestrial Magnetism and Atmospheric Electricity, (2) the type featuring the day other than normal by the letters b, p, o, and i for days marked by bay, rapid pulsations, long‐period oscillations, and irregular oscillations, respectively, and (3) the hour and minute of Greenwich mean time marking the beginning of a storm, the end of the storm being indicated in the foot‐note to the Table. The next two columns give the data relating to sunspots: (1) the number of groups of spots and (2) the total number of spots. It is to be noted that sunspot‐numbers such as those from Zürich can be obtained from the number of groups and spots given in the Table by the formula N = k (10g + s), where the mean value of k for Mount Wilson was 0.53 during 1936; during 1937 this value varied from 0.47 to 0.66 with an average value of 0.53.
Tucson Magnetic Observatory July to September, 1938
Authors: Hershberger John
Published: February 2008

(Latitude 32° 14′.8 N., longitude 110° 50′.1 or 7h 23m.3 W. of Gr.)

July 4–5—A moderate storm began gradually July 4, about 12h GMT, and ended about 08h, July 5. The activity was mostly of the short, quick, saw‐tooth variety, affecting H chiefly, D moderately, and Z slightly.
Geiger‐counter measurements in the upper atmosphere bearing upon the nature of the radiation from solar flares and radio fade‐outs
Authors: Johnson T. H. , Korff S. A.
Published: February 2008

The intensity of the penetrating radiation at an elevation of 20 km has been measured with a Geiger counter carried at a constant level by a balloon for a continuous interval including times before, during, and after a radio fade‐out. No effect was found, and the precision of the measurement excludes the possibility of an increase of intensity as great as two per cent. Assuming mass‐absorption of the ionizing radiation in a homogeneous atmosphere the limits of the absorption‐coefficient are determined from (a) the negative result of the balloon experiment, (b) the total ionization required in the region of high collision‐frequency for the absorption of radio energy, and (c) the fact that the E‐ and F‐layers are not appreciably altered as regards their ion‐density during the fade‐out. The analysis shows that the mass absorption‐coefficient must lie between 0.1 and 25 per gram, or if the solar‐flare radiation is of the nature of X‐rays the wave‐length must lie between 0.1 and 1.5Å.
Note on non‐cyclic change
Authors: Sapsford H. B.
Published: February 2008

In connection with the diurnal‐variation curves of the magnetic elements C. Chree1,2 has shown that usually there is a difference between the first and second midnights of the mean day and that this difference must be eliminated in order to obtain a curve which is strictly periodic in the 24 hours. This applies, also, to curves for other geophysical elements.

If ā0 and ā24 represent the mean values of the first and second midnights then

urn:x-wiley:00968013:media:tma32350:tma32350-math-0001
where N is the non‐cyclic change. The correction at any hour t is then

urn:x-wiley:00968013:media:tma32350:tma32350-math-0002
Provisional sunspot‐numbers for November, 1938, to January, 1939
Authors: Brunner W.
Published: February 2008

(Dependent alone on observation at Zürich Observatory and its station at Arosa)
Provisional solar and magnetic character‐figures, Mount Wilson Observatory October, November, and December, 1938
Authors: Nicholson Seth B. , Mulders Elizabeth Sternberg
Published: February 2008

The origin of the storm of October 7–8 is uncertain although it was probably caused by the very large sunspot‐group in latitude 17° north, which was 60° east of the central meridian when the storm began.

A chromospheric eruption of intensity 3 occurred at 18h 11m GMT, December 7, in a sunspot‐group 8° south of the equator and 10° west of the central meridian. At the same time a change occurred in the Earth's magnetic field at Mount Wilson similar to those which are usually caused by these eruptions. At 18h 11m GMT, H decreased 39 gammas in four minutes, recovering in the next 17 minutes.
The ionosphere at Watheroo, Western Australia May to December, 1938
Authors: Parkinson W. C. , Prior L. S.
Published: February 2008

Until April 13, 1938, recordings of ionospheric penetration frequencies and virtual heights were made on a fixed frequency of 4.8 mc/sec and on frequencies between 3.0 and 14.0 mc/sec in steps of 0.2 mc/sec by the manual multifrequency technique. On that date recording was discontinued for the installation of the automatic multi‐frequency recorder. This installation was sufficiently complete by May 20, 1938, to commence recording on four of the six bands, that is, from frequencies of 16.0 to 3.28 mc/sec. After the erection of the long antenna on July 19, 1938, the range of frequencies recorded was increased from 16.0 to 0.516 mc/sec and since that time recording has been continuous except for very short periods while adjustments and additions to the equipment were being made or when regular operations for maintenance were in progress.
Comparison of simultaneous ionosphere observations at Washington, D.C., and Deal, New Jersey
Authors: Schafer J. P. , Goodall W. M.
Published: February 2008

This paper discusses the observations obtained during cooperative ionospheric tests made at Washington, D.C., by the National Bureau of Standards and at Deal, New Jersey, by the Bell Telephone Laboratories. Curves are presented which show that the critical‐frequency values for the F‐ and F2‐regions were substantially the same at the two locations. Definite though small differences were noticeable during normal days, while during the violent phase of ionospheric storms the critical‐frequency values for Deal decreased more rapidly and to lower values than those observed at Washington.
Auroral corona, February 24, 1939
Authors: Paton James
Published: February 2008

During an auroral display on the evening of February 24, 1939, a corona in Gemini was photographed from Edinburgh at 21h 16m GMT, using a Störmer‐Krogness camera. By projection of the photograph and the use of “nets”, the coordinates of the radiation‐point have been found to be: Height, 64°.7±1°.0, and azimuth, 18°.2±2°.0 east of south. (The extent of the uncertainty is due to the rapidly changing shape of this corona, which made it difficult to trace the rays accurately from the projection of the photograph.) The remarkably large difference between these values and those for dip and declination obtained by the slow‐run La Cour record at Eskdalemuir at 21h 16m (69° 55′ north of west and 13° 18′ west of north, respectively) indicates the extent of the influence of the field, at heights of a few hundred km, due to the current‐system during an intense storm.
Watheroo Magnetic Observatory January to March, 1939
Authors: Parkinson W. C.
Published: February 2008

February 5–6—A moderate disturbance began with a sudden commencement in all three elements at 19h 50m GMT, February 5. The temporary lull in activity which occasionally follows a sudden commencement lasted until 9h, February 6, after which and until the end of the day all three traces were moderately disturbed, the maximum activity being shown between 13h and 15h. Throughout the disturbance the movements were of the “peak” and “bay” order rather than rapid fluctuations of short period. Ranges: D, 23′.0; H, 122 gammas; Z, 174 gammas.
International magnetic classification for years prior to 1890
Authors: van Dijk G.
Published: February 2008

Data for the magnetic classification prior to 1890, on the scale 0 to 7, have been received for the following observatories:

September 27, 1847–1889—Greenwich

1872–1889—Bombay

1875–1882 and 1884–1889—Melbourne

1877–1889—Zikawei

1880–1889—Toronto and Batavia

October 1882–September 1889—Los Angeles

1883–1889—Pare St. Maur and Mauritius

Stonyhurst has advised there is no opportuntiy of assigning character‐numbers to its records prior to 1906. Mauritius has stated that assignment of character‐numbers is not possible for the years 1875 to 1882.
Ionospheric characteristics at Huancayo, Peru, December, 1937, through December, 1938
Authors: Wells H. W. , Stanton H. E.
Published: February 2008

The first automatic multifrequency ionospheric equipment developed by the Department of Terrestrial Magnetism of the Carnegie Institution of Washington, was installed at the Huancayo Magnetic Observatory in the latter part of 1937 [see 1 under “References” at end of paper]. Continuous recordings over a limited range were started in November and operations over the entire frequency‐range, namely, 16.0 to 0.516 me/sec, were initiated in December, 1937 [2]. Since then the apparatus has operated continuously for 24 hours each day except for occasional short intervals necessary for maintenance to the equipment. The data, therefore, are entirely homogeneous. Quarterly reports on results of these investigations appear regularly in this Journal.
Summary of the year's work, Department of Terrestrial Magnetism, Carnegie Institution of Washington
Authors: Fleming J. A.
Published: February 2008

The Department during the year ended June 30, 1939, continued reduction and interpretation of accumulated data and experimental investigations in its laboratories and observatories. Its goal is the clearer understanding of terrestrial magnetism and terrestrial electricity and their correlated geophysical and cosmical phenomena. The work may be briefly summarized as follows:

Publications—In the course of specialized research it is essential from time to time to present a picture of progress. In this regard the Department has had a large share in the production of two important treatises which will satisfy a long‐felt need in the literature of geophysics. “Geomagnetism,” by S. Chapman and J. Barrels, will be published by the Oxford University Press probably early in 1940 and “Terrestrial Magnetism and Electricity” (volume VIII of the Physics‐of‐the‐Earth series sponsored by the National Research Council), prepared under the editorship of J. A. Fleming, by members of his staff and associates, was printed by the McGraw‐Hill Book Company for distribution in August 1939. These volumes—the former stressing the theoretical and mathematical aspects of terrestrial magnetism particularly and the latter the practical and descriptive aspects of terrestrial magnetism and electricity—will supplement each other in an authentic exposition of the subjects and their present status.
Tucson Magnetic Observatory, July to September, 1939
Authors: Hershberger John
Published: February 2008

July 3–6—The main part of this storm began rather indefinitely about 14 h GMT, July 4, but was preceded by a moderate disturbance beginning abruptly at 00h 38m, July 3, and ending about 8h, July 4. The first period was marked by several rather sharp excursions of H, amounting to 50 or 60 gammas. The second period lasted until about 4h, July 6. Except for a few hours near the middle of the second part of the storm, short‐period oscillations seemed to predominate.
Huancayo Magnetic Observatory, July to September 1939
Authors: Davies F. T.
Published: February 2008

July 3—There was a sudden commencement at 00h 40m GMT, July 3, when in two minutes H increased 25 gammas, Z increased 4 gammas, and D was not affected. Moderate disturbances with a number of large fluctuations in H continued until 21h.

July 4–5—There was a sudden commencement at 14h 08m GMT, July 4, when in four minutes D moved easterly 1′.8, H increased 83 gammas, and Z increased 3 gammas. A magnetic storm followed which continued until 20h, July 5, the last six hours being violently disturbed. A large number of fluctuations in H of large amplitude were recorded. Ranges: D, 12′; H, 304 gammas; Z, 17 gammas.
Magnetic Observatory, Capetown April to June, 1939
Authors: Ogg A.
Published: February 2008

Note: D and Z are negative; changes are in the algebraic sense.

April 1–2—Disturbances of small amplitude began at about 16h GMT, April 1, and continued until 24h, April 2, with small bays at about 18h and 23h each day.
Measurements of F2‐region ionization over New Zealand
Authors: White F. W. G. , Banwell C. J. , Peddie G. A.
Published: February 2008

(1) Introduction—Compared with the other two main ionized regions of the upper atmosphere (E‐ and F1‐regions) the highest and most richly ionized region (F2) presents theoretical problems which can be discussed adequately only when data collected in many different places of the Earth's surface can be examined simultaneously. The situation is similar to that of terrestrial magnetism in that the observations at one observatory cannot yield sufficient data upon which a theoretical discussion may be based.

Amongst the many observations which can be made with wireless waves reflected from the F2‐region the most fundamental are concerned with the measurement of the maximum charge‐density of this region. In view of the apparently anomalous behavior of this region it is of interest to investigate firstly the diurnal and secondly the seasonal variation of the maximum charge‐density of the region. Thirdly the wide fluctuations of this quantity which occur from day to day are of interest since they appear to be intimately connected with other geophysical occurrences.
Aux directeurs des observatoires magnétiques, contribuants à la publication “Caractère magnétique numérique des jours”
Authors: van Dijk G.
Published: February 2008

L'Association de Magnétisme et Electricité Terrestres de l'Union Géodésique et Géophysique Internationale a résolu, dans ses séances de septembre 1939 à Washington, de discontinuer la publication des caractères magnétiques numériques des jours, à partir de l'année 1940.

D'accord avec cette résolution, j'ai l'honneur de vous prier de ne plus envoyer vos tableaux avec les valeurs de HRH:10000, ZRZ:10000, et RD après le dernier trimestre de 1939.
Watheroo Magnetic Observatory October to December, 1939
Authors: Parkinson W. C.
Published: February 2008

October 13–15—A disturbance of moderate intensity began with a sudden commencement at 02h 04m GMT, October 13. The following sudden changes occurred: Westerly declination increased by 6′.0; H increased by 20 gammas; the numerical value of Z increased by 24 gammas. During the ensuing half‐hour very rapid fluctuations of moderate amplitude occurred, after which the movements were more subdued, almost calm conditions occurring between 11h and 14h, October 13. After this time the movements became much more irregular and of larger amplitude, the minimum value in H being reached at 03h 40m, October 14.
The diurnal variation and vertical distribution of atmospheric condensation‐nuclei
Authors: Yunker E. A.
Published: February 2008

The diurnal variation of the distribution of atmospheric condensation‐nuclei has been determined using a recording cloud‐chamber apparatus. The results show an increase of nuclei‐density with height in accordance with the suggestion of Gish and tentative vertical‐density distribution‐curves are proposed. The studies give further support to the convective theory of diurnal variation suggested by previous work. The variation of nuclei‐density with wind‐direction suggests a maritime origin for at least a portion of the nuclei.
On the contribution to the ionization at sea‐level produced by the neutrons in the cosmic radiation
Authors: Korff S. A.
Published: February 2008

Since neutrons constitute a numerically important component of the cosmic radiation [see 1 of “References” at end of paper], the question arises as to the amount of ionization in the atmosphere at sea‐level which they produce. This ionization will be produced in two ways: (a) By recoil‐nuclei produced by the neutrons in collisions; and (b) by the ionizing radiation ejected from nuclei as a result of neutron‐induced disintegrations. We may set limits to each of these contributions.

It is believed that most of the neutrons in the atmosphere at sea level are evaporated out of nuclei by the high‐energy cosmic radiation, and have initial energies of 10 to 30 Mev. It has been pointed out by Bethe, Korff, and Placzek [2] that these neutrons will first be inelastically scattered by nitrogen nuclei. In this process, the neutron enters the nitrogen nucleus, causes the ejection of one or more nuclear particles, and usually emerges with about four Mev energy. The bulk of the energy of the neutron is used in breaking up the binding of the nucleus, and hence is not transformed into ionization. The ionizing particles which are emitted will in general have energies which are small compared to the initial energy of the neutron, and it may be estimated [2] that of the order of five Mev per neutron will appear as ionization.
The ionosphere at Huancayo, Peru, October to December, 1939
Authors: Wells H. W. , Coile R. C.
Published: February 2008

This report on ionospheric conditions is in continuation of those published in preceding issues of this Journal submitting results of continuous multifrequency ionospheric recordings at the Huancayo Magnetic Observatory, Department of Terrestrial Magnetism, Carnegie Institution of Washington. The current data for October, November, and December, 1939, are obtained from recording for each hour of the day and for every day of the month except for short intervals necessary for maintenance of the equipment. This multifrequency apparatus sweeps through a frequency‐range from 16.0 to 0.516 mc/sec every 15 minutes.

Table 1 contains mean hourly values of virtual height, critical frequency, and lowest frequency received for the fourth quarter of 1939. Figure 1 presents the data of Table 1 in graphical form. The following general discussion of characteristics is pertinent.
Ionospheric characteristics at Huancayo, Peru, for the year 1939
Authors: Wells H. W. , Coile R. C.
Published: February 2008

Ionospheric characteristics at the Huancayo Magnetic Observatory (12° 02′.7 south, 75° 20′.4 west) of the Department of Terrestrial Magnetism, Carnegie Institution of Washington, for the year 1939 have been published in quarterly reports in this Journal [see 1 under “References” at end of paper]. The present paper is a recapitulation of the reports for the year 1939, and is a sequel to the analysis for the period December, 1937, through December, 1938 [2]. The photographic records have been obtained with multifrequency equipment sweeping over a frequency‐range of 16.0 to 0.516 mc/sec every 15 minutes continuously for 24 hours each day—except for occasional short intervals necessary for maintenance—since December, 1937.

This paper continues the method of presentation used in the annual report for 1938 [2]. The figures are relief maps illustrating mean diurnal variation in critical frequency or virtual height for each region. Full lines are contours of frequency or height, and dotted lines represent the curve of mean data for the month indicated. These figures afford an effective means of distinguishing the general characteristics and month‐to‐month trends by casual inspection.
Notes on isomagnetic charts: I—Their singular points and contour‐lines
Authors: Chapman S.
Published: February 2008

Some aspects of the geometry of isomagnetic charts (using isomagnetic in a wide sense) are considered, particularly as regards their ray‐poles and singular points—foci and nodes. Special types of singular points are shown to include circular foci, rectangular nodes, and cusps. Some suggestions are made regarding the construction of isomagnetic charts.
Notes on isomagnetic charts: II—The form and disposition of the nodal curves
Authors: Chapman S.
Published: February 2008

The form of the special isomagnetic lines which cross themselves (the nodal curves) is discussed, and the nature of the regions into which they divide the surface of the sphere. Geomagnetic illustrations of the simpler types of isomagnetic chart are cited.
The Ionosphere at Watheroo, Australia, October, 1940, to March, 1941
Authors: Parkinson W. C.
Published: February 2008

This report is a continuation of those already published in this Journal1 and gives monthly mean hourly values of the heights and penetration‐frequencies of the ionosphere as obtained by means of automatic multifrequency ionospheric recording apparatus located near Watheroo, Western Australia, in latitude 30° 19′.1 south, longitude 115° 52′.6 east of Greenwich, which operates over the frequency‐range 0.516 to 16.0 Mc/sec.

Table 1 gives the monthly mean hourly values of the height of maximum electron‐density (hmax), unconnected for retardation in lower regions2, and the minimum virtual height (hmin) for both the F1‐ and F2‐regions, the penetration‐frequencies for the E‐, F1‐, and F2‐regions, and the lowest frequency at which echoes were observed when that frequency was higher than 0.516 Mc/sec.
Alibag Magnetic Observatory, October to December, 1940
Authors: Rangaswami M. R.
Published: February 2008

October 26—A moderate disturbance began suddenly at 07h 23m GMT, October 26. H attained its maximum at 08h 02m and then began to fall with fluctuations to reach the minimum at 17h 20m. The disturbance ended at approximately 23h.5. Ranges: D, 4′.9; H, 185 gammas; Z, 45 gammas.

November 12–13—A moderate disturbance began with a sudden commencemt at 07h 06m GMT, November 12. H attained its maximum at 07h 38m, and then fell until llh.5, November 12, after which the oscillations became more pronounced. The minimum in H occurred at 05h 01m, November 13. The disturbance practically ended at 08h, November 13, although minor fluctuations continued for a period of short duration. Ranges: D, 3′.5; H, 145 gammas; Z, 117 gammas.
Magnetic Observatory, Capetown, October to December, 1940
Authors: Ogg A.
Published: February 2008

September 30–October 1—Disturbance began at 19h GMT, September 30. Marked bays developed on all traces at 01h, October 1, but otherwise the fluctuations were not large. At 11h 54m the disturbances became more marked and continued until 22h. H decreased 121 gammas in the period from 01h 52m to 18h 00m, while the decrease was 86 gammas from 15h 01m to 18h 00m.

October 3—Bays appeared on all traces at 18h GMT, October 3. The magnitude of the H‐bay was +38 gammas in forty minutes and then −20 gammas in sixty minutes.
Cape Town Magnetic Data
Authors: Ogg A.
Published: February 2008

The reduction and analysis of all data collected at the Magnetic Observatory, Cape Town, during the years 1933–40 have been completed with the exception of certain details with regard to the last six months of 1940, such as the international quiet and disturbed days which have not yet been announced.

The publication of the observations during the first four years was delayed by the printer and it is impossible, at the present time, owing to the existing war conditions, to proceed with their publication.
The Corpuscular Geomagnetic Index and Related Solar Changes
Authors: Clayton H. Helm
Published: February 2008

In that part of geomagnetic changes associated with solar changes the experts of the Department of Terrestrial Magnetism of the Carnegie Institution of Washington have distinguished two types of change, one associated with short‐wave solar radiation coming from flares visible on the surface of the Sun and the other attributed to electrified particles coming from the Sun. The first kind of disturbance travels with the velocity of light and reaches the Earth in a few minutes after the solar flares are seen. They affect only the sunlit side of the Earth and are principally noticeable in the equatorial regions of the Earth.

The second class of disturbance, associated with electrified particles, travels more slowly and effects the sunlit and dark sides of the Earth equally. These disturbances are most felt in the polar regions and when strong are associated with magnetic storms, auroras, and radio interruptions. The corpuscular radiation has been standardized to eliminate local effects and is now published by Science Service for every three hours as deduced from seven observatories scattered around the Earth and are called KA‐values. In addition complete values of K for the year 1938 and 1939 are published in Terrestrial Magnetism and Atmospheric Electricity for September, 1940, as compiled by Bartels, Heck, and Johnston.
Sitka Magnetic Observatory, October to December, 1941
Authors: Gebhardt Robert E.
Published: February 2008

(Latitude 57° 03′.0 N., longitude 135° 20′1 or 9h 01m.3 W. of Gr.)

October 11–12—A small disturbance began gradually at 06h GMT, October 11. The intensity increased gradually to maximum storminess at 10h. After 14h conditions began to return to normal. The trace remained moderately disturbed until 12h, October 12. The maximum K‐index registered during this period was 8.
Watheroo Magnetic Observatory, October to November, 1941
Authors: Parkinson W. C.
Published: February 2008

(Latitude 30° 19′.1 S., longitude 115° 52′.6 or 7h 43m.5 E. of Gr.)

October 31–November 1—This moderate disturbance began with a small sudden commencement at 03h 40m GMT, October 31. The movements thereafter were of no great amplitude until 17h when they gradually became more pronounced. The value of horizontal intensity decreased markedly after 22h. The fluctuations remained moderately active but nothing of importance was recorded until 10h, November 1, when a double bay of about one hour's duration occurred in all three elements. The double bay was repeated on a smaller scale between 13h 40m and 14h 50m on the same day. The traces rapidly became normal after 16h, November 1. Ranges: D, 19′.0; H, 173 gammas; Z, 149 gammas.
Notes on Isomagnetic Charts: VII—Mathematical Notes on Isoporic Charts and Their Singular Points
Authors: Chapman Sydney
Published: February 2008

Summary—The nature of the isoporic lines is examined for the magnetic potential V and for the magnetic elements D, H, I, Z, and F. In general the singular points on an isomagnetic chart are not singular points on the corresponding isoporic chart, and vice versa. In particular, the singular points for V, which are dip‐poles, are usually not singular points for its rate of change
. But the dip‐poles are singular points not only for D, H, and I (though not in general for Z and F) but also for
,
, and
(though not in general for
and
).

If the dip‐pole is moving, it is a double focus for
(which there takes all values from −∞ to +∞), and a non‐uniform ray‐pole for
and
the relation of the isopors to the velocity of the dip‐pole is indicated. If the dip‐pole is stationary, it is a non‐uniform ray‐pole for
and a conical focus or node for
(which there is zero) and for
.

The isopors for V, D, H, I, Z, and F for the field of a varying centered dipole are determined and illustrated. It is shown that in the region around an associated pair of local dip‐poles the isopors must be very complicated, those for D, for example, having at least eight singular points in the region. The isopors near the principal geomagnetic dip‐poles are discussed, and it is shown that in these regions certain isoporic charts appear to be inconsistent with theory.

The isoporic charts for 1922 for D and H given, by the Admiralty and by H. W. Fisk are compared and discussed. For 126 points uniformly spaced at 20° intervals the average numerical difference between the indications of the two charts is 56 per cent for
, and 69 per cent for H, of the average numerical value of D and H, respectively, at these points.
Height of Maximum Electron‐Density in the Ionosphere
Authors: Booker H. G.
Published: February 2008

It has been pointed out1 that, if one is willing to fit a parabolic maximum of electron‐density to an ionospheric region, an index of actual height of maximum electron‐density is given by the virtual height at five‐sixths of the penetration‐frequency. Monthly averages of the diurnal variation of this index, uncorrected for presence of lower regions, are now published for Watheroo (Western Australia)2 and Huancayo (Peru).3 The procedure has been criticized by Rawer,4 who states that a different index is used in Germany.

Accurate calculation of the actual height of maximum electrondensity from recorded multifrequency observations is a difficult matter and any procedure sufficiently simple for application to a large number of records is inevitably open to the charge of inaccuracy. Rawer correctly points out that, had we chosen to fit some non‐parabolic distribution of electron‐density, our index of the height of maximum electron‐density would have been affected. However, we are not irretrievably attached to the parabolic distribution and if it can be shown that some other distribution is more reliable and equally convenient we would be quite willing to change.
Tucson Magnetic Observatory, January to March, 1942
Authors: Nelson J. H.
Published: February 2008

(Latitude 32° 14′.8 N., longitude 110° 50′.1 or 7h 23m.3 W. of Gr.)

February 23–25—A moderate storm began at about 14h GMT, February 23, and ended at about 02h, February 25, with several long‐period and many short‐period oscillations. The main part of the disturbance stopped at about 10h, February 24, but considerable short‐period activity continued until the end of the storm. Ranges: D, 22′; H, 49 gammas; Z, 11 gammas.
Apia Observatory, January to March, 1942
Authors: Sapsford H. Bruce
Published: February 2008

(Latitude 13° 48′.4 S., longitude 171° 46′.5 or 11h 27m.1 W. of Gr.)

March 1–2—A sudden commencement at 07h 27m GMT, March 1, marked the beginning of a magnetic storm of short duration. The increase in the magnetic field was in two steps: H rose 68 gammas in one minute and then fell momentarily before rising, two minutes after the commencement, to a turning point 87 gammas above the undisturbed level. The Z‐trace showed the motion more clearly, the three turning points within two minutes of the start being quite distinct; they had values of 32, 22, and 33 gammas, respectively, above the pre‐storm level. The intensity of H and Z remained above normal for about two hours and then a rapid fall took place until about 10h, the minimum in Z occurring at 09h 51m. There were minor oscillations in H for further period until the minimum at 12h 54m. Very rapid small oscillations were superimposed on the larger movements from the start and continued until about 02h, March 2. D showed large fluctuations with a westerly trend in the early part of the storm. Ranges: D, 8′.2; H, 260 gammas; Z, 43 gammas.
On Alfven's theory of magnetic storms and of the aurora
Authors: Cowling T. G.
Published: February 2008

H. Alfven, in recent papers [Stockholm, Vet‐Ak. Handl., 18, No. 3 (1939) and No. 9 (1940)], attributes magnetic storms and auroras to a stream of ions and electrons emitted from the Sun, the electrons with energies about 108 volts and the ions with smaller energies. The theory differs from Chapman and Ferraro's theory of magnetic storms by taking into account the magnetic field of the Sun and supposing that the motion of any individual particle is hardly affected by the magnetic field due to the motion of other particles.

The outward motion of the stream from Sun to Earth is explained as due, not to the original outward velocities of the particles, but to electromagnetic effects. Alfven divides the motion of a particle in the Sun's magnetic field into four parts (see Note 1 on page 212):
Cheltenham Magnetic Observatory April to June, 1942
Authors: Hershberger John
Published: February 2008

April 2‐5—A moderate disturbance began rather indefinitely at about 11h GMT, April 2, and seemed to have ended twenty‐four hours later, the highest K‐index for this period being 5. But an abrupt renewal of activity occurred at 19h 18m, April 3, with a sudden increase in H. The disturbance ended at about 06h, April 5. There were several large bays, giving K‐indices of 6 for two successive three‐hour periods.

April 10‐11—A moderate disturbance began sharply at 23h 02m GMT, April 10, and ended at 16h, April 11. The first four three‐hour periods of April 11 had K‐indices of 5.
Watheroo Magnetic Observatory March, 1942
Authors: Parkinson W. C.
Published: February 2008

March 1‐2, 1942—This was a moderately large storm of short duration, which was chiefly noteworthy for the violence of the opening phases. A sudden commencement at 07h 26m 40s GMT, March 1, was shown in all three elements but the initial movements of the magnets were so rapid that the amounts and directions of motion cannot be assigned with any certainty; indeed, so rapidly did the horizontal intensity vary that the spot was invisible until the lamp‐slit was widened when the disturbance was first noted at 08h 20m. The maximum intensity of the disturbance occurred between 09h and 11h when the total range in H and Z was recorded. The elements continued to be generally disturbed until 06h on March 2, by which time the traces were again normal.
Magnetic Observatory, Hermanus, April to June, 1942
Authors: Ogg A.
Published: February 2008

April 2‐4—Small disturbances began at 04h 40m GMT, April 2, and continued 48 hours. There were sudden changes at 04h 39m, April 4, and afterwards the storm developed into one of considerable range. Sharp bays were formed on all traces with peaks at 20h 13m, April 4. The ranges on April 4 were: D, 20′.6; H, 174 gammas; Z, 129 gammas.
Some early contributions to the history of geomagnetism: I
Authors: Harradon H. D.
Published: February 2008

The writing of a detailed and comprehensive history of geomagnetism would present many difficulties, because the beginnings are almost hopelessly obscured by myths and legends and many important points are still subjects of uncertainty and controversy. Some light has been thrown on mooted questions by scholars in recent times, but much still remains to be clarified regarding the discovery of the directive power of the Earth's field and its practical application.1

There are, however, a number of documents which may be regarded as milestones in the development of geomagnetic knowledge and whose importance from a historical viewpoint is undisputed. Unfortunately, all these early writings have become extremely rare and the few extant copies are preserved in widely distributed libraries. In order to make them more generally available, G. Hellmann was led to reproduce, partly in facsimile, some of the more important contributions in his “Rara Magnetica” [Neudrucke von Schriften und Karten über Metorologie und Erdmagnetismus, No. 10, Berlin, Asher und Co. (1898)].