Abstract of team proposal.

A specific class of strong solar energetic particle (SEP) events are the ground-level enhancements (GLEs) in which solar ions are accelerated to energies sufficiently high to induce nucleonic cascades in the Earth’s atmosphere, whose secondaries can be registered by ground-based detectors, e.g., neutron monitors (NMs). Historically, GLEs have been analyzed using NM records, but different authors have used different model assumptions and methods. Significant progress in both observations and modelling of SEP events has been achieved in recent years, specifically using the data from space-borne instruments, whose measurements usually extend up to hundreds of MeV in energy, whilst the sea-level polar NMs respond to ions with energy over ~300 MeV/n. Therefore a gap exists between the response of most spacecraft instruments and NMs. Space-borne detectors PAMELA (2006 – 2016) and AMS-02 (2011 – until now) are able to measure the spectrum of high-energy SEPs encompassing the NM energy response, though with lower sensitivity and a rapidly varying directional and energy response caused by their low orbits. Generally, there are systematic differences between the results of GLE analyses performed with low-energy space-borne instruments and those derived from ground-based devices, as well as between different instruments and teams, particularly in the high-energy range of the SEP spectra. Strong SEP fluxes can cause terrestrial and space weather effects, resulting in energetic particle precipitation in the atmosphere, induced ionization, variation in atmospheric electrical properties, and increased radiation dose at flight altitudes. For reliable quantification of those effects, precise knowledge of SEP spectra is necessary, but a non-tolerable discrepancy persists, most likely due to the differences in the derived energy spectra used for inputs in the models of terrestrial/space weather effects. Within the scope of the project, we will bring together SEP measurements from NMs and the fleet of space-borne instruments such as the Solar and Heliospheric Observatory (SOHO), Solar and Terrestrial Relations Observatory (STEREO), Advanced Composition Explorer (ACE), Geostationary Operational Environmental Satellite (GOES), Alpha Magnetic Spectrometer (AMS-02), and Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA), which will be inter-calibrated to fill in the long-standing gap between NM and space-borne measurements. In result, we are going to produce verified and inter-calibrated spectra during strong SEP events which will provide the solar/space/solar-terrestrial physics and space weather communities with a necessary basis to deepen the current knowledge on the acceleration and transport of SEPs and to quantify the related space weather and terrestrial effects.