Statistical study on the ascending time of solar energetic particle events
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摘要: 选取1997-2006年共66个较大的缓变型太阳高能粒子(SEP)事件, 分析了不同条件下太阳高能粒子通量廓线上升时间与源区日面经向分布之间的相关关系, 研究了日冕物质抛射(CME)和耀斑在SEP上升阶段的作用特点.统计结果表明,大SEP事件的源区主要分布在太阳西半球, 特别是磁足点东西两侧45°范围内; 在高速太阳风条件下, 低能通道的通量上升时间与日面相对经度有较好的相关性,即离磁足点越远, 上升时间越长,而高能通道相关性则不明显; 全晕状CME产生的SEP事件对应的上升时间与源区位置没有明显的相关性, 而部分晕状CME伴随的SEP事件则与二次拟合曲线符合很好.分析表明,在缓变型SEP事件的通量上升阶段, 耀斑加速过程起着重要作用,这在部分晕状CME伴随的SEP事件中尤为显著.Abstract: A total of 66 great gradual Solar Energetic Particle events (SEPs) from 1997 to 2006 were selected for analysis. The correlations were analyzed between the ascending time of the SEPs in time profile and the heliographic longitude of the source active region. The Coronal Mass Ejection (CME) and flares were also investigated in the ascending stage of the SEP flux profile. The results of statistical analysis indicate that the source regions of these great SEPs are mainly distributed in the western hemisphere, particularly within the area from 45° east longitude to 45° west longitude relative to the magnetic footpoint. In the presence of fast solar wind, the ascending time in low-energy channel has a good correlation with the relative longitude and the ascending time increases with the distance from magnetic footpoint. However, the correlation is unobvious in high-energy channel. Correlations have not been observed between the ascending time of the SEPs associated with full halo CMEs and the source region longitude. However, the relations between the ascending time of the SEPs and source longitude are well fitted with quadratic curves. The analytical results show that the flare acceleration process played an important role in the gradual phase of SEP time profile, especially for the SEPs associated with partial halo CMEs.
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