THE ONSET TIMES OF FORBUSH-TYPE COSMIC RAY INTENSITY DECREASES

1959 ◽  
Vol 37 (9) ◽  
pp. 970-982 ◽  
Author(s):  
A. G. Fenton ◽  
K. G. McCracken ◽  
D. C. Rose ◽  
B. G. Wilson
Keyword(s):  
Daily Variation ◽  
Cosmic Ray ◽  
Consistent Pattern ◽  
Maximum Sensitivity ◽  
Geomagnetic Disturbances ◽  
Cosmic Ray Intensity ◽  
Early Stages ◽  
The Earth ◽  
Directional Anisotropy ◽  
Quiet Day

The onset times of a number of Forbush-type decreases observed at four widely spaced stations are compared, and it is shown that appreciable differences occur. The stations selected were Hobart, Mawson, Ottawa, and Sulphur Mountain. It was found that a consistent pattern is obtained for the events studied when the onset times are plotted as a function of the direction of maximum sensitivity of the recorders relative to the earth-sun line. This is interpreted as being due to a directional anisotropy that exists in the mechanism producing the decreases, at least in the early stages. The depression occurs first for particles arriving from directions between 30° and 120° west of the earth–sun line. The relation between these observations and geomagnetic disturbances and the quiet-day daily variation is discussed.

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 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.

scholarly journals Galactic Anisotropy of Cosmic Ray Intensity Observed by an Air Shower Experiment

2006 ◽  
Vol 23 (3) ◽  
pp. 129-134
Author(s):  
Mahmud Bahmanabadi ◽  
Mehdi Khakian Ghomi ◽  
Farzaneh Sheidaei ◽  
Jalal Samimi
Keyword(s):  
Daily Variation ◽  
Cosmic Ray ◽  
Cosmic Ray Intensity ◽  
Extensive Air Shower ◽  
Air Shower ◽  
The Earth ◽  
The Galaxy ◽  
Unidirectional Anisotropy ◽  
Galactic Cosmic Ray ◽  
Shower Array

AbstractWe have monitored multi-TeV cosmic rays by a small air shower array in Tehran (35°43′ N, 51°20′ E, 1200 m = 890 g cm−2). More than 1.1 × 106 extensive air shower events were recorded. These observations enabled us to analyse sidereal variation of the galactic cosmic ray intensity. The observed sidereal daily variation is compared to the expected variation which includes the Compton–Getting effect due to the motion of the earth in the Galaxy. In addition to the Compton–Getting effect, an anisotropy has been observed which is due to a unidirectional anisotropy of cosmic ray flow along the Galactic arms.

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.

scholarly journals 40. Separation of extra terrestrial variations in cosmic ray intensity and atmospheric effects by differential measurements by G–M telescopes

1958 ◽  
Vol 6 ◽  
pp. 386-391
Author(s):  
E. A. Brunberg
Keyword(s):  
Daily Variation ◽  
Cosmic Ray ◽  
The Other ◽  
Atmospheric Effects ◽  
Cosmic Ray Intensity ◽  
Difference Of Opinion

The daily variation of cosmic ray intensity can arise partly from atmospheric and partly from non-atmospheric effects. There is at present a difference of opinion whether this latter effect is completely due to extra terrestrial causes or not.The purpose of the present paper is to suggest a method by which the atmospheric effects could be separated from the other variations without any assumptions about the mechanism of the atmospheric influence.

A study of daily variation in cosmic ray intensity during high/low amplitude days

Pramana ◽  
2007 ◽  
Vol 68 (3) ◽  
pp. 407-422 ◽  
Author(s):  
Rajesh K Mishra ◽  
Rekha Agarwal Mishra
Keyword(s):  
Daily Variation ◽  
Cosmic Ray ◽  
Cosmic Ray Intensity ◽  
Low Amplitude

Time variations of directional cosmic ray intensity at low latitude - II. Time variations of east-west asymmetry

1961 ◽  
Vol 263 (1312) ◽  
pp. 118-126 ◽  
Keyword(s):  
Geomagnetic Storms ◽  
Daily Variation ◽  
Cosmic Ray ◽  
Middle Latitude ◽  
Geomagnetic Disturbance ◽  
Equatorial Station ◽  
Cosmic Ray Intensity ◽  
Primary Cosmic Radiation ◽  
Time Variations ◽  
East West

Changes of the energy spectrum of primary cosmic radiation can be followed through the time variations of east-west asymmetry of the μ -meson component at low latitudes. Such a study has been conducted for the first time at Ahmedabad during 1957-8. The changes of east-west asymmetry are associated with changes of the daily variation of cosmic ray in­tensity, of the daily mean neutron intensity measured at equatorial and middle latitude stations, of the index of geomagnetic disturbance and of the horizontal component of the earth’s magnetic field. The study indicates that days with high east-west asymmetry are associated with geomagnetically quiet days and a cosmic ray daily variation consistent with its being produced by an anisotropy of primary radiation outside the influence of the geomagnetic field. On such days, the daily variation produced by the anisotropy, as observed at an equatorial station, has a significant diurnal as well as a semi-diurnal component. High east-west asymmetry and associated anisotropy occur 3 to 5 days before the arrival of solar corpuscular beams which envelop the earth. Days with low east-west asymmetry occur about 3 to 4 days after the onset of cosmic ray storms associated with geomagnetic storms, usually of the SC type.

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.

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