TRANSIENT DECREASES IN COSMIC RAY INTENSITY DURING THE PERIOD OCTOBER 1956 TO JANUARY 1958

1959 ◽  
Vol 37 (5) ◽  
pp. 569-578 ◽  
Author(s):  
A. G. Fenton ◽  
D. C. Rose ◽  
K. G. McCracken ◽  
B. G. Wilson
Keyword(s):  
Forbush Decrease ◽  
Cosmic Ray ◽  
Statistical Accuracy ◽  
Short Term ◽  
Cosmic Ray Intensity ◽  
The Earth ◽  
Controlling Mechanism ◽  
Intensity Changes ◽  
Recurrence Tendency ◽  
Cosmic Ray Flux

Recent nucleon intensity data obtained from high counting rate recorders at Ottawa and Hobart, and subsidiary stations, have been examined for evidence for the superposition of transient decreases. It is concluded that, with the statistical accuracy now available due to the high counting rates, it is possible to distinguish two types of transient decreases in the observed variations, superimposed upon the slower 11-year intensity changes. One of these is an almost symmetrical event lasting up to 2 weeks and exhibiting a recurrence tendency of about 27 days, while the other is the more abrupt Forbush decrease which recovers over a period of several days. The evidence indicates that the intensity-controlling mechanism responsible for these short-term transient changes is able to influence the cosmic ray flux at the earth independently of other events that may be in progress at the time. There is also evidence that the physical process controlling the Forbush type of decrease operates over a volume large compared with the earth because the intensity changes at places as far apart as Ottawa, Canada, and Hobart, Tasmania, show changes that are the same within the accuracy of the measurements.

scholarly journals Tritium and Argon-39 in Stone and Iron Meteorites

1969 ◽  
Vol 24 (2) ◽  
pp. 234-244 ◽  
Author(s):  
St. Charalambus ◽  
K. Goebel ◽  
W. Stötzel-Riezler
Keyword(s):  
Cosmic Ray ◽  
Decay Rates ◽  
Earth Atmosphere ◽  
Iron Meteorites ◽  
Production Rates ◽  
Cosmic Ray Intensity ◽  
The Earth ◽  
Cosmic Ray Flux

Tritium and argon-39 measurements of stone and iron meteorites are reported and discussed. The tritium values of stone meteorites are in general higher than those found in other laboratories. The tritium decay rates in irons were low but a relatively high tritium value was measured in the rim of the meteorites. Factors which may influence the production rates are discussed and it is concluded that the average cosmic-ray flux which irradiated the meteorites must be at least a factor of two higher than the values reported by MacDonald for the cosmic-ray intensity at the top of the earth atmosphere.

STUDY OF FORBUSH DECREASE EVENT AND ASSOCIATED GEOMAGNETIC FIELD AND COSMIC RAY INTENSITY VARIATION

2005 ◽  
Vol 20 (29) ◽  
pp. 6717-6719 ◽  
Author(s):  
S. K. MISHRA ◽  
D. P. TIWARI ◽  
S. C. KAUSHIK
Keyword(s):  
Forbush Decrease ◽  
Intensity Variation ◽  
Cosmic Ray ◽  
Strong Relationship ◽  
Geomagnetic Disturbances ◽  
Slow Recovery ◽  
Short Term ◽  
Cosmic Ray Intensity ◽  
Transient Disturbances ◽  
Term Basis

Transient decrease in cosmic ray intensity following by a slow recovery typically lasting for several days is identified as Forbush decrease (Fd) event. As a result the geomagnetic index (Dst) decreased up to 300 nT, indicating a large geomagnetic storm and the percentage Fd decrease has gone to 16% giving rise a cosmic ray storm. Both events coincided with interplanetary conditions. Therefore, a systematic study has been performed to investigate the variation of cosmic ray intensity along with the interplanetary and geomagnetic disturbances. Results indicate a strong relationship between geomagnetic activity and Forbush decrease on short-term basis. Two types of interplanetary transient disturbances, namely magnetic cloud events and bidirectional events are analyzed to study the short-term changes in the solar wind (SW) plasma components as well as in cosmic ray intensity.

An Anomalous Forbush Decrease

1968 ◽  
Vol 1 (4) ◽  
pp. 146-148
Author(s):  
J. E. Humble
Keyword(s):  
Forbush Decrease ◽  
Cosmic Ray ◽  
Ground Level ◽  
Magnetic Activity ◽  
Solar Origin ◽  
The Earth ◽  
Cosmic Ray Flux

Ground level detectors observed several major changes in the primary cosmic-ray flux during November 4960. Large increases, of solar origin, occurred on November 12 and 15, and a smaller one on November 20. The galactic flux in the region of the Earth was severely reduced by a Forbush decrease on November 12, and remained notably depressed until November 25. Considerable magnetic activity was observed throughout the period. Several models have been proposed to account for these observations.

Directional measurements of the cosmic-ray daily variation at a vertical depth of 60 m.w.e. in London

1968 ◽  
Vol 46 (10) ◽  
pp. S788-S793 ◽  
Author(s):  
D. S. Peacock ◽  
J. C. Dutt ◽  
T. Thambyahpillai
Keyword(s):  
Solar Minimum ◽  
Daily Variation ◽  
Vertical Direction ◽  
Cosmic Ray ◽  
The Sun ◽  
Statistical Accuracy ◽  
Daily Variations ◽  
The Earth ◽  
Cosmic Ray Flux ◽  
Very High

Semicubical telescopes pointing in the vertical direction and inclined cubical telescopes pointing in the east and north directions have been employed to measure the cosmic-ray daily variation at an underground site in London. Although the statistical accuracy of the measured daily variations is not very high, there are strong indications that during 1965, which was the year of maximum cosmic-ray flux associated with the last solar minimum, tire upper limiting rigidity of the corotation anisotropy (with time of maximum at 1800 h) was reduced to such low values that a Compton–Getting effect due to the motion of the earth around the sun became observable. Also, the atmospheric contribution to the measured solar daily variations appears to be very small. There is no evidence for an enhancement of the observable sidereal daily variation associated with the lowering of the upper limiting rigidity of the corotation anisotropy.

Anisotropy in cosmic-ray intensity associated with Forbush decreases

1968 ◽  
Vol 46 (10) ◽  
pp. S854-S858 ◽  
Author(s):  
T. Mathews ◽  
J. B. Mercer ◽  
D. Venkatesan
Keyword(s):  
Daily Variation ◽  
Forbush Decrease ◽  
Cosmic Ray ◽  
Turbulent Plasma ◽  
The Sun ◽  
The West ◽  
Cosmic Ray Intensity ◽  
Rate Of Development ◽  
The Earth ◽  
Scattering Centers

A study of the Forbush decrease of 23 September 1966 shows that the predecrease anisotropy developed from a direction 85° to the west of the sun–earth line. The rate of development of the anisotropy suggests that the "turbulent" plasma producing the Forbush decrease occupied a volume of diameter ≈0.2–0.3 AU. If the plasma clouds away from the earth produced the anisotropy at the earth, then it is reasonable to attribute a part of the highly variable daily variation in cosmic-ray intensity to such distant scattering centers.

A New Determination of Muon Directional Coupling Coefficients

1968 ◽  
Vol 1 (4) ◽  
pp. 154-157
Author(s):  
D. J. Cooke ◽  
A. G. Fenton
Keyword(s):  
Cosmic Rays ◽  
Solar System ◽  
Cosmic Ray ◽  
Accurate Information ◽  
Coupling Coefficients ◽  
The Earth ◽  
Directional Coupling ◽  
Cosmic Ray Flux ◽  
Primary Cosmic Rays

Primary cosmic rays passing through the solar system carry with them valuable information about solar and astrophysical phenomena in the form of intensity and spectral variations. In order that this information be efficiently extracted from observations of the directional cosmic-ray flux at the surface of the Earth, it is essential to have accurate information available to enable the relating of the observed secondary cosmic-ray directions of motion and intensity to those outside the range of the disturbing terrestrial influences.

scholarly journals 36. The 27-day variation in cosmic ray intensity and in geomagnetic activity

1958 ◽  
Vol 6 ◽  
pp. 332-344 ◽  
Author(s):  
Scott E. Forbush
Keyword(s):  
Harmonic Analysis ◽  
Geomagnetic Activity ◽  
Statistical Significance ◽  
Cosmic Ray ◽  
Magnetic Activity ◽  
Effective Number ◽  
Cosmic Ray Intensity ◽  
Fourth Group ◽  
Sunspot Minimum ◽  
Recurrence Tendency

The amplitude of the average 27-day wave in cosmic ray intensity, at Huancayo, Peru, and its phase relative to that for the 27-day wave in international magnetic character figure (ICF) is determined from results of harmonic analysis of data for each of 246 intervals (or solar rotations) of 27 days. From these data, the variability of which is essential for tests of statistical significance, the amplitude of the average 27-day wave in cosmic ray intensity and its phase relative to that in geomagnetic activity is determined for each of three groups of solar rotations selected according to the average of the amplitudes of the 27-day waves in magnetic activity. A fourth group contained only 27-day intervals in which large cosmic ray decreases occurred. Relative to that in magnetic activity, the phase of the 27-day wave in cosmic ray intensity is found for the averages, to be the same for the four groups.The maxima of the average cosmic ray waves occur about 1·5 days after the minima of the corresponding waves in ICF. In general, the amplitude of the average 27-day wave in cosmic ray intensity, in the co-ordinate system in which its phase is relative to that of the 27-day wave in ICF tends to be greater for the selected groups of rotations with larger average ICF amplitudes. For most years near sunspot minimum the amplitude of the 27-day cosmic ray wave does not differ significantly from zero.Bartels found for 27-day waves in ICF the effective number of statistically independent 27-day waves for N successive solar rotations to be N/3; the number found for cosmic ray intensity is N/2. Thus, on the average the 27-day recurrence tendency is less for cosmic ray intensity than for magnetic activity.

Cosmic ray flux at the Earth in a variable heliosphere

2008 ◽  
Vol 41 (8) ◽  
pp. 1171-1176 ◽  
Author(s):  
K. Scherer ◽  
H. Fichtner ◽  
B. Heber ◽  
S.E.S. Ferreira ◽  
M.S. Potgieter
Keyword(s):  
Cosmic Ray ◽  
The Earth ◽  
Cosmic Ray Flux
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