Abstract
The shadows of the Sun and Moon have been detected in the ID TeV cosmic-ray flux by the Tibet air shower array at an altitude of 4300 m above sea level. The observation covers the period 1990 June-1993 October, which almost coincides with a near-maximum and decreasing phase of the latest solar activity cycle. Using the data obtained in this period, we examined a yearly variation of the Sun's shadow, and found for the first time that the position of the Sun's shadow changed considerably every year with the phase of the solar activity. A different variation of the Sun's shadow was also found between the "away" and "toward" sectors of the interplanetary magnetic field. These results seem to suggest a causal relation between the shadow's movement and the changing inclination of the helio-spheric current sheet of the large-scale magnetic field. Further observation with higher statistics will provide a new clue to obtain direct information on the relation between a time variation of the large-scale structure of the solar and interplanetary magnetic fields and the phase of the solar activity cycle.
Original language | English |
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Pages (from-to) | 954-958 |
Number of pages | 5 |
Journal | Astrophysical Journal |
Volume | 464 |
Issue number | 2 PART I |
Publication status | Published - 1996 |
Externally published | Yes |
Keywords
- Cosmic rays
- Interplanetary medium
- Magnetic fields
- Solar wind
- Solar-terrestrial relations
ASJC Scopus subject areas
- Space and Planetary Science