New reconstruction of event-integrated spectra (spectral fluences) for major solar energetic particle events

TL;DR

This paper presents a comprehensive revision of spectral fluences for major solar energetic particle events from 1956 to 2017, using updated data and a new reconstruction method to improve accuracy and reliability.

Contribution

It introduces a novel reconstruction method with an improved neutron-monitor yield function and provides a detailed, tabulated spectral fluence dataset for major SEP events.

Findings

Revised spectral fluences for 1956-2017 GLEs with improved accuracy.

Application of a new reconstruction method and Monte Carlo uncertainty assessment.

Provision of a publicly accessible, tabulated spectral fluence database.

Abstract

Fluences of solar energetic particles (SEPs) are not easy to evaluate, especially for high-energy events (i.e. ground-level enhancements, GLEs). Earlier estimates of event-integrated SEP fluences for GLEs were based on partly outdated assumptions and data, and they required revisions. Here, we present the results of a full revision of the spectral fluences for most major SEP events (GLEs) for the period from 1956 -- 2017 using updated low-energy flux estimates along with greatly revisited high-energy flux data and applying the newly invented reconstruction method including an improved neutron-monitor yield function. Low- and high-energy parts of the SEP fluence were estimated using a revised space-borne/ionospheric data and ground-based neutron monitors, respectively. The measured data were fitted by the modified Band function spectral shape. The best-fit parameters and their uncertainties were assessed using a direct Monte Carlo method. As a result, a full reconstruction of the event-integrated spectral fluences was performed in the energy range above 30 MeV, parametrised, and tabulated for easy use along with estimates of the 68% confidence intervals. This forms a solid basis for more precise studies of the physics of solar eruptive events and the transport of energetic particles in the interplanetary medium, as well as the related applications.