Anisotropies in Cosmic Radiation

Dattner, A.; Venkatesan, D.

doi:10.1111/j.2153-3490.1959.tb00025.x

Cited by 9 publications

(3 citation statements)

References 14 publications

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“…Many workers have attempted to derive relationships between the mean daily variation and the level of solar and geomagnetic activity (Sarabhai and Kane, 1953;Sarabhai et al, 1954;Dorman, 1957;Dattner and Venkatesan, 1959;Venkatesan and Dattner, 1959;Duggal and Pomerantz, 1963;Kolomeets et al, 1965;Duggal and Pomerantz, 1966;Fenton, 1968;Messerschmidt, 1970;Jacklyn et al, 1971). It is evident in Figure 10 that over a period of thirty years, the amplitude of the diurnal anisotropy was significantly lower during each of the sunspot minimum epochs, in accord with the results obtained during the last solar cycle with a variety of detectors.…”

Section: Variation With a Period Of One Solar Cyclementioning

confidence: 99%

The cosmic ray solar diurnal anisotropy

Pomerantz

Duggal

1971

Space Sci Rev

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This paper reviews the present state of knowledge concerning the diurnal and semidiurnal variations in the galactic cosmic ray intensity. The analytical procedures that are required for extracting from the original data the desired information concerning the characteristics of the anisotropies outside the magnetosphere are described. These include corrections for atmospheric fluctuations, the determination of the amplitudes and phases of the daily variations, and their interpretation in terms of the free space anisotropies that give rise to them. The experimental results concerning the 24-h wave, including its long-term variations with periods of one and two solar cycles, and the characteristics of the total dmrnal anisotropy are then discussed. The semidmrnal amsotropy is considered next. Transient anisotropies which manifest themselves as day-to-day variations, recurrence tendencies, cosmic ray storms, and diurnal variation trains, and which can introduce appreciable changes in the spectral parameters, are also of interest. The evolution of theoretical models developed to account for the diurnal and semidiurnal anisotropies, and fluctuations thereof, are then discussed in the light of the experimental results. Finally, the general features that are now well established, and the nature of the remaining problems, are summarized.

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Section: Variation With a Period Of One Solar Cyclementioning

confidence: 99%

The cosmic ray solar diurnal anisotropy

Pomerantz

Duggal

1971

Space Sci Rev

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“…According to Equation (4), if the magnetic field is nearly in the ecliptic plane then B e ≈ B and A e ≈ r g |G z | (Datter & Venkatesan 1959). For median rigidity protons detected by PSNM, at 35 GV, the Larmor radius was about 0.1 AU for the average magnetic field, 7 nT, near the leading edge of the HSS during DOY 177-178, and from G z = −5.5% AU −1 the gradient anisotropy should be about 0.55%, which is in good agreement with the observed enhancement in the DA.…”

Section: Carrington Rotation 2070 and 2071mentioning

confidence: 99%

Corotating Solar Wind Structures and Recurrent Trains of Enhanced Diurnal Variation in Galactic Cosmic Rays

Yeeram

Ruffolo

Sáiz

et al. 2014

ApJ

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Data from the Princess Sirindhorn Neutron Monitor at Doi Inthanon, Thailand, with a vertical cutoff rigidity of 16.8 GV, were utilized to determine the diurnal anisotropy (DA) of Galactic cosmic rays (GCRs) near Earth during solar minimum conditions between 2007 November and 2010 November. We identified trains of enhanced DA over several days, which often recur after a solar rotation period (∼27 days). By investigating solar coronal holes as identified from synoptic maps and solar wind parameters, we found that the intensity and anisotropy of cosmic rays are associated with the high-speed streams (HSSs) in the solar wind, which are in turn related to the structure and evolution of coronal holes. An enhanced DA was observed after the onset of some, but not all, HSSs. During time periods of recurrent trains, the DA was often enhanced or suppressed according to the sign of the interplanetary magnetic field B, which suggests a contribution from a mechanism involving a southward gradient in the GCR density, n, and a gradient anisotropy along B × ∇n. In one non-recurrent and one recurrent sequence, an HSS from an equatorial coronal hole was merged with that from a trailing mid-latitude extension of a polar coronal hole, and the slanted HSS structure in space with suppressed GCR density can account for the southward GCR gradient. We conclude that the gradient anisotropy is a source of temporary changes in the GCR DA under solar minimum conditions, and that the latitudinal GCR gradient can sometimes be explained by the coronal hole morphology.

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“…Should the amplitude not be constant it would still be diminished to a minimum through the process of averaging. Dattner and Venkatesan (1959) have listed seven possible components of the diurnal variation. The existence of these components has been derived from the theory by Alfv~n (1954) concerning the origin of cosmic rays.…”

Section: H0)mentioning

confidence: 99%

The Daily Variation of the Cosmic Ray Nucleonic Component at Murchison Bay and Uppsala

Sandström

Dyring

Lindgren

1960

TellusA

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In both places the monitors were of the standard pattern with 12 proportional counters filled with 97 per cent enriched B10F8. The first and second harmonics of the mean daily variation have been determined both for yearly periods and for each sun rotation period. Vector sum diagrams for the first harmonics in the latter case are given covering the intervals 31 Aug. 1956 to 15 Aug. 1959 for Uppsala and 13 Sept. 1957 to 29 April 1959 for Murchison Bay. In some instances a considerable phase shift has taken place from one sequence of sun rotation periods to another. These phase shifts were not contemporary at the two stations. The first harmonic of the 12-month means displays a high degree of constancy with only a small secular phase shift. The amplitudes of the second harmonics are very small. Conditions are especially favourable concerning the deviation in the earth’s magnetic field of the particles registered by the Murchison Bay monitor. Accordingly it has been possible to determine the direction of the anisotropy with a fairly good accuracy. The Murchison Bay records do not show any prominent phase shift with the Kp index. Concerning Uppsala, days with [Kp]max ≤ 1+ have a later time of maximum than other days. The influence of single days with an abnormal daily variation is discussed.

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Anisotropies in Cosmic Radiation

Cited by 9 publications

References 14 publications

The cosmic ray solar diurnal anisotropy

The cosmic ray solar diurnal anisotropy

Corotating Solar Wind Structures and Recurrent Trains of Enhanced Diurnal Variation in Galactic Cosmic Rays

The Daily Variation of the Cosmic Ray Nucleonic Component at Murchison Bay and Uppsala

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