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

TL;DR

This study analyzes neutron monitor data to estimate the energy spectrum, anisotropy, and pitch-angle distribution of solar energetic particles during two major ground level enhancements in 2000 and 2006, using a new yield function and inverse modeling.

Contribution

It introduces a new neutron monitor yield function and a comprehensive method for analyzing solar energetic particle characteristics during ground level enhancements.

Findings

Estimated energy spectra and anisotropy axes for GLE 59 and GLE 70.

Derived pitch-angle distributions and rigidity spectra over time.

Achieved reasonable agreement with previous studies.

Abstract

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 use 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 computations of cosmic ray particles propagation in a model magnetosphere with the MAGNETOCOSMICS code; computation of the neutron monitor model responses and derivation of 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 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 as well their possible application is included.