Analysis of the ground level enhancements on 14 July 2000 and on 13 December 2006 using neutron monitor data

摘要

On the basis of neutron monitor data we estimate the energy spectrum,anisotropy axis direction and pitch-angle distribution of solar energeticparticles during two major ground level enhancements (GLE 59 on 14 July 2000and GLE 70 on 13 December 2006). For the analysis we use a newly computedneutron monitor yield function. The method consists of several consecutivesteps: definition of the asymptotic viewing cones of neutron monitor stationsconsidered for the data analysis by computations of cosmic ray particlespropagation in a model magnetosphere with the MAGNETOCOSMICS code; computationof the neutron monitor model responses and derivation of the solar energeticparticle characteristics on the basis of inverse problem solution. Thepitch-angle distribution and rigidity spectrum of high-energy protons areobtained as function of time in the course of ground level enhancements. Acomparison with previously reported results is performed and reasonableagreement is achieved. A discussion of the obtained results is included as welltheir possible application is included.