Simulation of long-term cosmic-ray intensity variation

Solar Physics ◽  
1990 ◽  
Vol 125 (2) ◽  
pp. 409-414 ◽  
Author(s):  
H. Mavromichalaki ◽  
E. Marmatsouri ◽  
A. Vassilaki
Keyword(s):  
Intensity Variation ◽  
Cosmic Ray ◽  
Cosmic Ray Intensity

Solar modulation of galactic cosmic rays near solar minimum (1965)

1968 ◽  
Vol 46 (10) ◽  
pp. S887-S891 ◽  
Author(s):  
V. K. Balasubrahmanyan ◽  
D. E. Hagge ◽  
F. B. McDonald
Keyword(s):  
Cosmic Rays ◽  
Solar Minimum ◽  
Intensity Variation ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
Solar Modulation ◽  
Time Behavior ◽  
Cosmic Ray Intensity ◽  
Radial Gradient

The results of the continuous monitoring of the intensity of cosmic rays (of energy > 50 MeV) with identical G-M counter telescopes flown in satellites IMP I, II, and III and OGO-I are presented along with the differential spectrum studies obtained from balloon flights at Fort Churchill and from satellites. A comparison of the time behavior of the G-M counter data with Deep River neutron monitor data suggests the presence of a "hysteresis" type of behavior due to spectral changes occurring near solar minimum. The existence of this "hysteresis" suggests that the radial gradient of cosmic rays near the earth could be much smaller than the ~ 10%/AU obtained by O'Gallagher and Simpson (1967) and O'Gallagher (1967) at higher energies. The long-term intensity variation of cosmic rays seems to follow the Ap index rather closely in phase, in contrast to sunspot numbers which display a pronounced phase difference with cosmic-ray intensity. The differential spectra of protons and He nuclei have been analyzed in terms of two different models for the propagation in the interplanetary medium. The modulations indicated by the present data seem to disagree with a diffusion coefficient proportional to βR where β and R are the velocity and rigidity of the particle respectively (Jokipii 1966).

scholarly journals Prediction of galactic cosmic ray intensity variation for a few (up to 10-12) years ahead on the basis of convection-diffusion and drift model

2005 ◽  
Vol 23 (9) ◽  
pp. 3003-3007 ◽  
Author(s):  
L. I. Dorman
Keyword(s):  
Interplanetary Space ◽  
Intensity Variation ◽  
Cosmic Ray ◽  
Particle Energy ◽  
Cosmic Ray Intensity ◽  
Convection Diffusion ◽  
Drift Model ◽  
Galactic Cosmic Ray ◽  
Near Future

Abstract. We determine the dimension of the Heliosphere (modulation region), radial diffusion coefficient and other parameters of convection-diffusion and drift mechanisms of cosmic ray (CR) long-term variation, depending on particle energy, the level of solar activity (SA) and general solar magnetic field. This important information we obtain on the basis of CR and SA data in the past, taking into account the theory of convection-diffusion and drift global modulation of galactic CR in the Heliosphere. By using these results and the predictions which are regularly published elsewhere of expected SA variation in the near future and prediction of next future SA cycle, we may make a prediction of the expected in the near future long-term cosmic ray intensity variation. We show that by this method we may make a prediction of the expected in the near future (up to 10-12 years, and may be more, in dependence for what period can be made definite prediction of SA) galactic cosmic ray intensity variation in the interplanetary space on different distances from the Sun, in the Earth's magnetosphere, and in the atmosphere at different altitudes and latitudes.

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.

Time variations of directional cosmic ray intensity at low latitudes: I. Comparison of daily variation of the intensity of cosmic rays incident from east and west

1961 ◽  
Vol 263 (1312) ◽  
pp. 101-117 ◽  
Keyword(s):  
Geomagnetic Field ◽  
Daily Variation ◽  
Cosmic Ray ◽  
Local Source ◽  
Cosmic Ray Intensity ◽  
Low Latitudes ◽  
Long Term Changes ◽  
Time Variations ◽  
East And West

A study has been, conducted at Ahmedabad during 1957 and 1958 of the time variations of meson intensity incident from east and west at 45° to the vertical. A characteristic differ­ence of about 6 h in the diurnal time of maximum for the east and west directions is observed to occur on many days and this has been interpreted as signifying an anisotropy of primary radiation caused by a source outside the influence of the geomagnetic field. However, there are many days on which the daily variation has a maximum near noon for both directions. On such days the predominant influence is that of a local source situated within the influence of the geomagnetic field. The local source is associated with geomagnetically disturbed days. Long-term changes in the daily variation are found to be similar for the east, vertical and west directions.

scholarly journals Solar activity, 27-day variation and long term modulation of cosmic ray intensity

Solar Physics ◽  
1970 ◽  
Vol 11 (1) ◽  
pp. 151-154 ◽  
Author(s):  
V. K. Balasubrahmanyan ◽  
D. Venkatesan
Keyword(s):  
Solar Activity ◽  
Cosmic Ray ◽  
Cosmic Ray Intensity
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