Variation of Sun shadow in the Solar Cycle 23 observed with the Tibet air shower array

According to many solar observations, the solar activity, during the Solar Cycle 23, is gradually declining to the quiet phase from the high state in 2000-2004. The Tibet air shower array has been continuing the observation of the shadow that cosmic rays make in the direction of the sun or the moon since 1991. We have shown the influence of the magnetic field around the sun, the interplanetary and the geomagnetic fields for the sun shadow at the multi-TeV region. We discuss the variation of the Sun's shadow with the Gnevyshev gap (GG) in the maximum phase of the Solar Cycle 23. Unfortunately, the bottom in GG corresponds to off-observation period. Nonetheless, we found the anti-correlation between the significance of the Sun's shadow and the variation of the magnetic field intensity around GG, although the statistical significance is not so high. It is expected that a detailed analysis of the Sun's shadow will reveal interesting features of the anti-correlation.