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

¹ University of Oulu, Oulu, Finland
e-mail: koldobskiy@gmail.com
² National Research Nuclear University MEPhI, Moscow, Russia
³ St. Petersburg State University, St Petersburg, Russia
⁴ University of Turku, Turku, Finland
⁵ Ioffe Physical-Technical Institute, 194021 St. Petersburg, Russia

Received: 3 December 2020
Accepted: 8 January 2021

Abstract

Aims. 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 Earlier estimates of event-integrated SEP fluences for GLEs were based on partly outdated assumptions and data, and they required revisions.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 to 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.

Methods. 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.

Results. 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.

Conclusions. 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.