Solar Diurnal Variation Research Articles

Intensity Problem in the Deflection of Cosmic Rays in the Solar Magnetic Field

Assuming uniform parallel beam of cosmic rays at infinity is deflected in the general magnetic field of the sun, cosmic-ray intensities at each point of the earths' orbit were calculated. Problem was treated only in the equatorial plane for simplicity. As the intensities change with season, the solar diurnal variation averaged over all season never tends to zero due to the heliomagnetic deflection of cosmic rays.

Diurnal Variation of Vertical Cosmic Rays

It is well known that anomalous solar diurnal variation SD of cosmic rays appears at the time of geomagnetic storms. We confirmed the existence of SD about the cosmic-ray intensities of total component and high energy component penetrating 90cm lead absorber measured with narrow angle telescope directed vertically. Amplitude of SD of the total component is the largest and the time of maximum intensities of that of the high energy component is the latest. The phases of SD are different with five different kinds of cosmic-ray meters in our country. This can be understood qualitatively by the deflections of cosmic rays in the earth's magnetic field. Year to year variation of phase of SD and long-time variation of amplitude of mean diurnal variation were investigated.

The Sidereal Correlation of Extensive Air Showers

About 3 × 105 extensive air-shower events were recorded at Auckland (altitude 40m, latitude 37° S.) with 3 counter trays at the corners of a 4 m triangle, each of sensitive area 2360 cm2, in the period February 1951 to February 1952. The results show a solar diurnal amplitude of (1.45 ± 0.25)% with maximum at (2.7 ± 0.6) hours local solar time and a sidereal diurnal amplitude of (1.10 ± 0.26)% with maximum at (19.8 ± 0.9) hours local sidereal time (standard errors). By introducing the concept of antisidereal time (there are 364.2 antisidereal days per year) an allowance is made for the seasonal amplitude modulation of the solar diurnal variation. When this correction is applied, the true sidereal diurnal amplitude becomes (1.43 ± 0.38)% with maximum at (17.6 ± 1.0) hours local sidereal time. The results indicate a maximum in the cosmic ray intensity when the galactic plane is overhead.

Sidereal Correlation of High-Energy Cosmic Rays

EXTENSIVE air showers have been recorded at Auckland (altitude 40 m.) during the period February 1951–February 1952 inclusive, with three counter trays each of sensitive area 2,360 cm.2 placed at the corners of an equilateral triangle with 4 m. sides. About 3 × 105 events have been recorded. Averaged over the year, the results show a solar diurnal variation of 1.46 ± 0.16 per cent (first Fourier amplitude with statistical probable error), with the maximum at 2.9 ± 0.4 hr. local solar time. This correlates well with temperature.

The solar diurnal variation in the amplitude of sudden commencements of magnetic storms at the geomagnetic equator

The solar diurnal variation in the amplitude of sudden commencements of magnetic storms at the geomagnetic equator

Some time variations of cosmic rays

Cosmic ray observations made at Canberra have been examined for variations according to sidereal time and compared with an analysis of results from other localities. The analysis was made by noting annual changes in the phase and amplitude of the first harmonic of the apparent solar diurnal variation. A regular change of phase with a period of one year may be caused by a true sidereal diurnal variation. Such regular changes have been found in the results for several stations. However these changes do not occur simultaneously over the globe. The changes differ in phase by about 180° in the northern and southern hemispheres with a tropical station having an intermediate position. This suggests that the variations are not sidereal but are of a solar-seasonal nature. Changes in the amplitude of the solar diurnal variation display no obvious world-wide regularity in the results examined.

Theory of lunar effects and midday decrease inF2 ion-density at Huancayo, Peru

It is shown that the diurnal variation of the earth's magnetic field gives rise to forced diffusion of ions in the F2 region. Calculations indicate that at Huancayo, Peru, this diffusion may account for the midday decrease in F2 critical frequency observed there. To test this theory, the F2 data from Huancayo were examined to determine if, when the solar and lunar magnetic diurnal variations are in phase, the midday values of F2 critical frequency are lower than when the variations are out of phase, as called for by the theory. The predicted effect was verified by the observations.

Sidereal Variations of Cosmic Rays

DUPERIER1 has analysed the first harmonic of the apparent solar diurnal variation of cosmic rays at London, using a method due to Thompson2. He finds that the first harmonic for any month has three components, namely, (i) a mean solar vector M, (ii) a vector, A, altering the amplitude of M, and (iii) a vector, P, controlling the change of phase of M. The P vector may arise from either (a) a sidereal diurnal variation, (b) an annual solar variation, or (c) a combination of these effects. This communication discusses the interpretation to be placed on the P vector, by comparing Duperier‘s figures for London with the results obtained at Canberra.

Solar Magnetic Field and Diurnal Variation of Cosmic Radiation

Solar Magnetic Field and Diurnal Variation of Cosmic Radiation

Solar and Sidereal Diurnal Variations of Cosmic Rays

THE study of the solar diurnal variations of cosmic rays, which has been described elsewhere1, has now been extended, in respect of the first harmonic, by arranging in six groups the data for 860 complete days during the period May 1941–April 1944. The first group consists of the data for January and February of all three years, the second group of data for March and April of all three years, and so on, the material for each day consisting of 12 bi-hourly numbers of triple coincidences.

Persistent Solar Rotation Period of 26.875 Days and Solar-Diurnal Variation in Terrestrial Magnetism

FROM an examination of the solar-diurnal variation in the horizontal force of the terrestrial magnetic field at Godhavn, Greenland, it has been established that the amplitude of the daily variation due to disturbance, SD, varies in a regular way over a period of 26.875 days, so that the mean amplitude of SD on the ninth day of the period is four times as great as that on the nineteenth day. The investigation was made in the following way: the days in the period (seven sequences of 27 days followed by one of 26 days) were numbered 0-26, and the material used consisted of 185 sequences of 26.875 days covering the epoch July 1, 1926-September 11, 1940 (eight periods in 1931 in which the material had not yet been rally prepared being omitted). Only the sequences for the summer months, May-August, were used at first. The daily variation due to disturbance, SD = S - Sq, was determined for the 1st day of the period (mean of the 0th, the 1st and the 2nd day), the 4th day (mean of 3rd, 4th, 5th day), 7th, 10th, 13th, 16th, 19th, 21st, 25th day for the total epoch (66 series), SD was analysed harmonically, the non-cyclic variation being eliminated at first, and the two first Fourier coefficients were determined (the 24- and the 12-hour term). Fig. 1 a gives the amplitudes c1, and c2, as functions of the number of the day. Next the material was divided in three groups: the disturbed summers 1926-31, the quiet summers 1932-36, and the disturbed summers 1937-40. The resulting values for c1 are given in Fig. 1, b, c and d, where the marked points represent the observed values and the full curve is the curve from Fig. 1 a multiplied by a convenient factor. Figs. 1 b-d confirm that the period is persistent throughout the fifteen summers. Comparison of 1 b, 1 c and 1 d makes it probable that the length of the period has an error of ± 0.025 day.

The Daily Variation of Irregular Disturbances of the Earths's Magnetic Field at Bombay

Besides the quiet‐day solar diurnal variation and the variations associated with magnetic storms, the intensity of the Earth's magnetic field at any place is subject to many irregular, short‐period fluctuations. The paper contains an analysis of the diurnal variation of these irregular disturbances during the eleven‐year period 1923–33. As a measure of the disturbance, the departures of the hourly ranges of the horizontal forces from the mean hourly range on the five international quiet days in that particular month were used. In calculating the disturbance, due regard was paid to the sign of the change of the element during the hour. The diurnal variations of the irregular disturbances depend on the season of the year and on the sunspot‐activity. These variations are analyzed and compared with the results of disturbance diurnal variation in higher latitudes. The main conclusions that emerge from the analysis are:(i) The hour of minimum disturbance occurs early in the morning usually between 04h to 05h or 05h to 06h local time and that of the maximum near about noon.(ii) There are two secondary maxima, one at 16h to 18h and another at about 22h to 23h local time.(iii) Analyzing the results according to month, the day maximum is most pronounced in the months April to August. In the winter months, there is a tendency for the variation to approach the European type (as shown by the analysis of the data of Eskdalemuir (magnetic latitude Φ=59°.5) and of Wilhelmshaven (Φ = 54°.5) in which there is one minimum in the morning at about 09h local time and a maximum in the evening at about 22 h.(iv) If days of magnetic character 2 are excluded, the diurnal variations are similar, but the late evening maximum is suppressed, leaving the noon maximum more pronounced.It is generally believed that “in the latitudes between the two auroral zones, that is, up to at least 65° magnetic latitude, Di has a simple diurnal variation with its maximum in the evening; as the auroral zone is approached the hour of maximum gets later, from about 21h at 55° to midnight at 70°. Up to this latitude the form of the daily variation of Di does not vary much either with season or with the general intensity of magnetic disturbance” [Chapman]. The present analysis of the Bombay data shows that in low magnetic latitudes, the main variation is a maximum near noon with a minimum a little before sunrise. The evening maximum of temperate latitudes is superposed on this simple variation.It is suggested that the maxima of disturbance‐variation at Bombay at about noon and in the afternoon are associated with the maxima of ion‐density in the E‐ and F1‐layers and in the F2‐layer, respectively. The late evening maximum is presumably due to fluctuations in F2‐layer caused by electrified particles from the Sun concentrating on the night side of the Earth on account of the deflecting action of its magnetic field.

Spherical harmonic analysis of the Sq‐variations, May‐August 1933

§ 1. The present paper gives the results of the spherical harmonic analysis of the quiet solar diurnal variations (Sq) of the Earth's magnetic field for the summer months, May to August, 1933. Schuster [see 1 of “References” at end of paper] was the first to apply in 1889 Gauss's expansion in terms of spherical harmonics to the analysis of diurnal variations. The spherical harmonic analysis of the Earth's permanent and transient magnetic fields is of the utmost importance, first, because it permits generalizing the empirical data in the form of an analytical expression and, second, because it offers information regarding the structure of this field (its potential and its origin). The spherical harmonic analysis of the diurnal variations has therefore been repeatedly undertaken by many investigators [2 to 7]; but from time to time, with accumulation of new observational data (of greater reliability, or referring to other epochs), it becomes desirable to have recourse to new analyses.

Present status of the theory of the effect of the earth's magnetic field on cosmic rays

The present communication is intended to cover a brief summary of the results obtained through analysis of the motion of charged particles in the earth's magnetic field and includes the following topics: 1. (a) The main cone, in any direction within which particles of a given energy may arrive at a given point on the earth. Latitude and azimuthal effects. Special cases of the latter: north-south and east-west asymmetries. The ratio of positive and negative primaries. 2. (b) The shadow cone, outside of which no particles of a given energy may arrive at a given point on the earth. 3. (c) The penumbra, i.e. the region intermediate between the main cone and the shadow cone in which certain directions are allowed and the others forbidden. 4. (d) The eccentricity of the earth's magnetic center and the longitude effect. The position of the earth's magnetic center. The earth's magnetic quadripole. 5. (e) The earth's magnetic field and the galactic rotation effect. 6. (f) The sun's magnetic field and some of the consequences of its existence. The knee of the latitude effect. Solar diurnal and annual variations. 7. (g) Preliminary communication on magnetic storms and cosmic ray intensity.

A Critical Analysis for Sidereal Time Variations of Cosmic Rays on the Pacific

The problem of distinguishing a true sidereal diurnal variation in cosmic-ray intensity from a seasonal change in the amplitude of the solar diurnal variation is approached from the standpoint of the harmonic dial type of analysis. It is shown that the regular cyclic arrangement of the datum points taken in chronological order serves as a criterion for the presence of the sidereal time variation. Cosmic-ray data taken on the Pacific Ocean during 1936 by A. H. Compton and R. N. Turner are shown to contain no sidereal diurnal component larger than the experimental error.

Solar Diurnal Variation of Cosmic-Ray Intensity as a Function of Latitude

The cosmic-ray data collected by A. H. Compton and R. N. Turner on the Pacific Ocean from March 17, 1936 to January 18, 1937 have been analyzed for a possible change with latitude of the solar diurnal intensity variation. A new geomagnetic latitude curve is shown based on these data and designed to remove periodic fluctuations due to unequal distribution of data with time. A method of combining data from a wide latitude range is developed and applied. Solar diurnal variation curves for latitudes ranging from 54.7\ifmmode^\circ\else\textdegree\fi{} N to 40\ifmmode^\circ\else\textdegree\fi{} S (geomagnetic) show no substantial variation in either amplitude or phase. The mean amplitude of the first harmonic of a Fourier analysis is found to be 0.24 percent with time of maximum being 14 hr. 06 min.

Lunar diurnal variation in Earth‐currents at Huancayo and Tucson

The lunar diurnal variation in earth‐current flow at Huancayo and Tucson has been determined from the records for the year 1932, near the sunspot‐minimum. Using the method employed by Chapman for the magnetic elements, a definite lunar diurnal variation of markedly double period is found in both components of the potential‐gradient at both stations. Harmonic analyses of the mean curves show that at Huancayo the amplitude of the second harmonic is about one‐sixth that of the solar diurnal variation for the same year, while the amplitudes of the first, third, and fourth harmonics are negligibly small. At Tucson the amplitude of the second harmonic is about one‐fifth that of the solar diurnal variation for the northward component which is the principal component at that station.The manner in which the lunar diurnal variation changes with the phase of the Moon was also examined. For both components at Huancayo, curves constructed for the four main phases of the Moon show a marked increase in activity during daylight hours and a corresponding diminution during the night so that the individual curves are no longer semi‐diurnal. For Tucson the curves for the individual phases of the Moon, as determined from this single year's record are too irregular to show the changes definitely, but do indicate that they are less pronounced at this higher‐latitude station. As a check on this point the lunar diurnal variation at Tucson was redetermined by the method applied by Egedal to the data from Ebro. In this method the lunar diurnal variation is obtained from the records for the individual hours of the solar day. Using the hours from 12 to 24 the lunar diurnal variation found is in good agreement with that obtained by the usual method. Comparing the lunar diurnal variation obtained separately by this method during daylight, 12h to 18h, with that obtained during the night, 18h to 24h, there is found only a slight decrease in amplitude from day to night and very little change in phase. These results are in agreement with those obtained by the first method and also with the revised conclusions reached by Egedal from his studies of the Ebro records.

The lunar atmospheric tide at five Japanese stations

AbstractThe lunar atmospheric tide at five Japanese stations, Taihoku, Naha, Kumamotu, Tokio and Sapporo, in latitudes 25°, 26°, 33°, 36°, 43°N., have been found from bi‐hourly values of the barometric pressure extending, in the aggregate for the five stations, over 193 years. The harmonic coefficients for the solar diurnal barometric variation at these stations have also been calculated.

Solar Diurnal Variation of Cosmic-Ray Intensity as a Function of Latitude

Solar Diurnal Variation of Cosmic-Ray Intensity as a Function of Latitude

The lunar atmospheric tide in the Azores, 1894‐1932

AbstractThe lunar atmospheric tide is determined at two stations in the Azores, namely, Ponta Delgada (38° N., 26° W.) and Santa Cruz (39° N., 31° W.), from 39 to 26 years' bi‐hourly data (all days) for the barometric pressure. The mean results are respectively 22 sin (2t + 55 °) and 18 sin (2t + 58°) in microbars, so that high tide occurs 72 and 65 (solar) minutes after lunar transit. As at most other stations, the tide is distinctly later near the December solstice than at other times. The probable errors of these mean results are 1.6 and 2.2 microbars.The harmonic coefficients for the first four components of the solar diurnal variation are also given.