Study on the cosmic ray intensity variation using scintillation counters for air shower observation

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.

Download Full-text

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

Canadian Journal of Physics ◽

10.1139/p68-375 ◽

1968 ◽

Vol 46 (10) ◽

pp. S887-S891 ◽

Cited By ~ 10

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).

Download Full-text

On the Solar Cycle Variation of the Solar Diurnal Anisotropy of Multi-TeV Cosmic-ray Intensity Observed with the Tibet Air Shower Array

EPJ Web of Conferences ◽

10.1051/epjconf/201920808012 ◽

2019 ◽

Vol 208 ◽

pp. 08012

Author(s):

M. Amenomori ◽

X. J. Bi ◽

D. Chen ◽

T. L. Chen ◽

W. Y. Chen ◽

...

Keyword(s):

Solar Cycle ◽

Cosmic Ray ◽

Local Solar Time ◽

Solar Cycle Variation ◽

Cosmic Ray Intensity ◽

Air Shower ◽

23Rd Solar Cycle ◽

Diurnal Anisotropy ◽

Shower Array ◽

Air Shower Array

We analyze the temporal variation of the solar diurnal anisotropy of the multi-TeV cosmic-ray intensity observed with the Tibet air shower array from 2000 to 2009, covering the maximum and minimum of the 23rd solar cycle. We comfirm that a remarkable additional anisotropy component is superposed on the Compton-Getting anisotropy at 4.0 TeV, while its amplitude decreases at higher energy regions. In constrast to the additional anisotropy reported by the Matsushiro experiment at 0.6 TeV, we find the residual component measured by Tibet at multi-TeV energies is consistent with being stable, with a fairly constant amplitude of 0.041% ± 0.003% and a phase at around 07.17 ± 00.16 local solar time at 4.0 TeV. This suggests the additional anisotropy observed by the Tibet experiment could result from mechanisms unrelated to solar activities.

Download Full-text

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

Publications of the Astronomical Society of Australia ◽

10.1071/as06015 ◽

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.

Download Full-text