太阳宇宙线地面增强事件(GLE72)峰值能谱研究

Research on the peak energy spectrum of the solar cosmic ray ground level enhancement event(GLE72)

太阳宇宙线地面增强事件(GLE)能谱可以提供宇宙线加速和传播过程的重要信息.利用GOES15卫星和地面中子堆实验数据分析了最近一次GLE事件(2017年9月GLE72)的质子峰值能谱,得到卫星观测能段的质子峰值能谱的能谱指数为1.88,中子堆观测能段的能谱指数为4.86.利用高能太阳粒子的二重加速机制对能谱结果进行了定性的理论解释.GLE72质子峰值能谱结果对LHAASO等大型地面宇宙线观测阵列中更高能量粒子具有重要参考价值.

The ground level enhancement(GLE)event energy spectrum provides important information about the acceleration and propagation of cosmic ray.In this paper,we analyze the proton flux peak energy spectrum of recent GLE event(2017.09 GLE72)by using GOES15 satellite and neutron monitor experiment data.The method of adjacent averaging smoothing and weighted average are applied to study GOES15 satellite data,and obtain the flux peak and flux peak time.By fitting,the energy spectrum index of proton flux peak is 1.88 in the satellite observation energy range.Again,the energy spectrum index of the neutron monitor observation energy range,4.86,is obtained by using the new neutron monitor yield function.It can be seen that the peak energy spectrum index given by satellites in the lower energy range(5–433 MeV)is much smaller than that given by the neutron monitor in the higher energy range(0.44–19 GeV).This means that,the energy spectrum in the lower energy range is harder than that in the higher energy range.Hence,the results of the energy spectrum could be explained qualitatively by the re-acceleration mechanism of high energy solar particles.In the low corona region,first,the particles released by the solar flare are accelerated,and the energy spectrum index of the high-energy range is twice that of the low-energy range.Then part of the solar high energy particles from the low corona enter into the CME,where they will be re-acceleration by the shock wave.The GLE72 event high energy range energy spectrum index given by the neutron monitor experiment is 4.86,so the energy spectrum index in low energy range should be 4.86/2=2.43.However,the low energy range energy spectrum index is 1.88(lower than 2.43 in low energy range).The reason may be that the energy spectrum index is further reduced due to the re-acceleration effect in the shock wave generated by the CME.The observation of GLE event is one of the main research subjects of the Large High Altitude Air Shower Observatory(LHAASO).Also,the GLE72 proton peak energy spectrum results provide important information to observe solar high energy particles in the LHAASO experiment.