Propagation of a large Forbush decrease in cosmic-ray intensity past the Earth, Pioneer 11 at 34 AU, and Pioneer 10 at 53 AU

1992 ◽  
Vol 19 (14) ◽  
pp. 1423-1426 ◽  
Author(s):  
James A. Van Allen ◽  
R. Walker Fillius
Keyword(s):  
Forbush Decrease ◽  
Cosmic Ray ◽  
Cosmic Ray Intensity ◽  
The Earth ◽  
Pioneer 10

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.

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.

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.

The Accuracy of Radiocarbon Dates

Antiquity ◽  
1963 ◽  
Vol 37 (147) ◽  
pp. 213-219 ◽  
Author(s):  
W. F. Libby
Keyword(s):  
Magnetic Field ◽  
Solar System ◽  
Cosmic Ray ◽  
Average Life ◽  
Radiocarbon Dates ◽  
Cosmic Ray Intensity ◽  
Rapid Mixing ◽  
The Past ◽  
The Earth ◽  
The Magnetic Field

The first test of the accuracy of dates obtained by the radiocarbon technique was made by determining whether dates so obtained agreed with the historical dates for materials of known age (n. 1). The validity of the radiocarbon method continues to be an important question, especially in the light of the numerous results that have been accumulated and the greater precision of the technique during the past few years (n. 2).The radiocarbon content of the biosphere depends on three supposedly independent geophysical quantities: (i) the average cosmic ray intensity over a period of 8000 years (the average life of radiocarbon) as measured in our solar system but outside the earth's magnetic field (n. 1); (ii) the magnitude (but not the orientation, because of the relatively rapid mixing over the earth's surface) of the magnetic field in the vicinity of the earth, averaged over the same period (n. 1,3); and (iii) the degree of mixing of the oceans during the same period (n. 1). The question of the accuracy of radiocarbon dates therefore is of interest to geophysicists in general as well as to the archaeologists, geologists and historians who use the dates.Previous workers in this area (n. 1, 2) have reported some discrepancies, and it is the purpose here to consider the matter further.

Time variations of directional cosmic ray intensity at low latitudes - III. Interpretation of solar daily variation and changes of east-west asymmetry

1961 ◽  
Vol 263 (1312) ◽  
pp. 127-135 ◽  
Keyword(s):  
Energy Spectrum ◽  
Interplanetary Space ◽  
Daily Variation ◽  
Cosmic Ray ◽  
Local Source ◽  
Cosmic Ray Intensity ◽  
The Earth ◽  
Low Latitudes ◽  
Time Variations ◽  
East West

The daily variation of cosmic ray intensity at low latitudes can under certain conditions be associated with an anisotropy of primary radiation. During 1957-8, this anisotropy had an energy spectrum of variation of the form aϵ -0.8±0.3 and corresponded to a source situated at an angle of 112 ± 10° to the left of the earth-sun line. The daily variation which can be associated with a local source situated along the earth-sun line has an energy spectrum of variation of the form aϵ 0 . Increases in east-west asymmetry and the associated daily variation for east and west directions can be explained by the acceleration of cosmic ray particles crossing beams of solar plasma in the neighbourhood of the earth. For beams of width 5 x 10 12 cm with a frozen magnetic field of the order of 10 -4 G, a radial velocity of about 1.5 x 108 cm/s is required. The process is possible only if the ejection of beams takes place in rarefied regions of inter­ planetary space which extend radially over active solar regions. An explanation of Forbush, type decreases observed at great distances from the earth requires similar limitation on the plasma density and conductivity of regions of interplanetary space. The decrease of east-west asymmetry associated with world-wide decreases of intensity and with SC magnetic storms is consistent with a screening of the low-energy cosmic ray particles due to magnetic fields in plasma clouds.

scholarly journals Precursory signals of Forbush decreases with and without shock wave

2021 ◽  
pp. 57-63
Author(s):  
Dimitra Lingri ◽  
Helen Mavromichalaki ◽  
Anatoly V. Belov ◽  
Eugenia A. Eroshenko
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Interplanetary Magnetic Field ◽  
Selection Criteria ◽  
Forbush Decrease ◽  
Cosmic Ray ◽  
Abrupt Increase ◽  
Cosmic Ray Intensity ◽  
Similarities And Differences ◽  
Solar Disturbances

Many previous studies have shown that before the beginning of a Forbush Decrease (FD) of the cosmic ray intensity, a precursor signal can be observed. All these surveys were focused on FDs that are associated with a sudden storm com- mencement (SSC). In this work we demonstrate that precursors could also be observed in events without a SSC that is determined by an abrupt increase of the interplanetary magnetic field. The type of precursory signals and their diversity among the events are the main purpose of this study. We try to figure out similarities and differences on the signals and the associated events from both categories in the last fifty years, from 1969 to 2019, using the same selection criteria of the under investigation FDs. Simultaneously the orientation of the upcoming solar disturbances in comparison to the way they configure the increase of the interplanetary magnetic field and create these signals are discussed.

scholarly journals Anomalous Forbush effects from sources far from Sun center

2008 ◽  
Vol 4 (S257) ◽  
pp. 451-456
Author(s):  
E. Eroshenko ◽  
A. Belov ◽  
H. Mavromichalaki ◽  
V. Oleneva ◽  
A. Papaioannou ◽  
...  
Keyword(s):  
Solar Wind ◽  
Cosmic Ray ◽  
The Sun ◽  
Geomagnetic Disturbances ◽  
Cosmic Ray Intensity ◽  
The Earth ◽  
The Common ◽  
Solar Wind Parameters ◽  
Significant Disturbance ◽  
Forbush Effect

AbstractThe Forbush effects associated with far western and eastern powerful sources on the Sun that occurred on the background of unsettled and moderate interplanetary and geomagnetic disturbances have been studied by data from neutron monitor networks and relevant measurements of the solar wind parameters. These Forbush effects may be referred to a special sub-class of events, with the characteristics like the event in July 2005, and incorporated by the common conditions: absence of a significant disturbance in the Earth vicinity; absence of a strong geomagnetic storm; slow decrease of cosmic ray intensity during the main phase of the Forbush effect. General features and separate properties in behavior of density and anisotropy of 10 GV cosmic rays for this subclass are investigated.

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