太阳质子峰值流量的极值分布

The Extreme Value Distribution of Solar Proton Peak Fluxes

采用极值统计学方法分析了过去四个太阳活动周[(1965—2005)]中每个太阳活跃年发生的最大质子事件,发现它们的峰值流量服从极值分布,其分布函数表述为:p(x)=1-exp{-exp[-0.686(x-7.263)]}.式中随机变量x是峰值流量的自然对数,并且用此分布函数讨论了大流量质子事件的重现期,发现理论预测与实际观测值吻合得很好。

A study has been carried out to analyze 27 solar proton events occured in solar active years with the largest annual peak flux no less than a few hundred pfu at the earth＇s orbit that were measured between 1965 and 2005. This study has been done by means of extreme value statistical theory method. It is formulated that the lar- gest annual proton peak flux obeys the extreme distribution, its distribution function is p （x） = 1 - exp / - exp [ - 0. 686 （x - 7. 263 ） ] } ,where the quantity x is the natural logarithm of the solar proton peak flux with energy 〉 10 MeV. Based on this formula the recurrence interval of hazard proton events is discussed, the calculated recurrence interval is in agreement with the observed one.