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arXiv 1612.02446physics.space-phastro-ph.SR
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地能级增强分析(GLE):极端太阳高能粒子事件具有硬谱

Analysis of Ground Level Enhancements (GLE): Extreme solar energetic particle events have hard spectra

E. Asvestari, T. Willamo, A. Gil, I. G. Usoskin, G. A. Kovaltsov, V. V. Mikhailov, A. Mayorov

摘要:

自20世纪50年代以来,全球中子监测网记录了近70次宇宙射线的地能级增强(GLE),描绘了太阳高能粒子(SEP)的各种能谱。在这里,我们研究了GLE的事件积分强度(计算为计数率相对过剩,平均在所有可用的极性中子监测器,并表示在100小时)和太阳粒子能谱的硬度之间的统计关系。对于每个事件的积分全向事件积分注量的粒子与能量超过30 MeV($F_{30}$)和超过200 MeV($F_{200}$)的计算使用重建的光谱,和两个注量之间的比率被认为是一个简单的指标事件的硬度。我们还使用GLE 71(2012年5月17日)的直接PAMELA数据,以带函数的形式提供了频谱估计的理由。我们发现,虽然有没有明确的强度和硬度之间的关系,弱事件,所有的强事件与强度大于100 \%* 小时的特点是由一个非常硬的频谱。这意味着对于所有极端GLE事件,可以安全地假设硬谱,例如,过去使用宇宙成因同位素数据研究的那些。

英文摘要:

Nearly 70 Ground Level Enhancements (GLEs) of cosmic rays have been recorded by the worldwide neutron monitor network since the 1950s depicting a big variety of energy spectra of solar energetic particles (SEP). Here we studied a statistical relation between the event-integrated intensity of GLEs (calculated as count-rate relative excess, averaged over all available polar neutron monitors, and expressed in percent-hours) and the hardness of the solar particle energy spectra. For each event the integral omnidirectional event-integrated fluences of particles with energy above 30 MeV ($F_{30}$) and above 200 MeV ($F_{200}$) were computed using the reconstructed spectra, and the ratio between the two fluences was considered as a simple index of the event's hardness. We also provided a justification of the spectrum estimate in the form of the Band-function, using direct PAMELA data for GLE 71 (17-May-2012). We found that, while there is no clear relation between the intensity and the hardness for weak events, all strong events with the intensity greater 100 \%*hr are characterized by a very hard spectrum. This implies that a hard spectrum can be securely assumed for all extreme GLE events, e.g., those studied using cosmogenic isotope data in the past.

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