Successive measurements of cosmic-ray antiproton spectrum in a positive phase of the solar cycle

The energy spectrum of cosmic-ray antiprotons (p¯'s) has been measured by BESS successively in 1993, 1995, 1997 and 1998. In total, 848 p¯'s were clearly identified in energy range 0.18-4.20 GeV. From these successive measurements of the p¯ spectrum at various solar activity, we discuss about the effect of the solar modulation and the origin of cosmic-ray p¯'s. The p¯/p ratios showed no distinctive year-to-year variation during the positive Sun's polarity phase.