Analysis of the Ground-Level Enhancements on 14 July 2000 and 13 December 2006 Using Neutron Monitor Data

On the basis of neutron monitor data, we estimate the energy spectrum, anisotropy axis direction, and pitch-angle distribution of solar energetic particles during two major ground-level enhancements (GLE 59 on 14 July 2000 and GLE 70 on 13 December 2006). For the analysis we used a newly computed neutron monitor yield function. The method consists of several consecutive steps: definition of the asymptotic viewing cones of neutron monitor stations considered for the data analysis by computing the cosmic ray particle propagation in a model magnetosphere with the MAGNETOCOSMICS code, computing the neutron monitor model responses, and deriving the solar energetic particle characteristics on the basis of inverse problem solution. The pitch-angle distribution and rigidity spectrum of high-energy protons are obtained as a function of time in the course of ground-level enhancements. A comparison with previously reported results is performed and reasonable agreement is achieved. A discussion of the obtained results is included.