Approaches to forecasting radiation risk from Solar Energetic Particles Silvia Dalla (1), Mike Marsh (2) & Timo Laitinen (1) (1) University of Central Lancashire, Preston, UK (2) Met Office, Exeter, UK

Background A number of SEP forecasting models that include a description of SEP propagation have been developed in recent years Typical output of these models are SEP intensities versus time and fluences How to translate physics outputs into actual radiation impact?

Required SEP properties For calculations of radiation doses, information on the SEP energy spectrum is required up to high energies (ideally with time evolution) US NRC Report on Space Radiation Risk in the New Era of Space Exploration, 2008

Impact scenarios Effects on spacecraft electronic components Effects on humans

SEP module (obtains fluxes and fluences at a given location in the heliosphere) Magnetospheric transport module (for LEO, not discussed here) Radiation module Required components

Example approach: EMMREM Schwadron et al, 2010

EMMREM 26 Oct 2003 events GOES 1 AU observations fed to SEP transport model SEP fluxes at Mars obtained and passed to BRYNTRN code BRYNTRN calculates doses for Al shielding + 10 g/cm 2 water (simulating soft tissue in human body) (PourArsalan et al 2010)

EMMREM dose outputs PourArsalan et al, 2010

Example approach: SEPEM Radiation effects analysis tools based on the MULASSIS code (for protons) (Crosby et al 2015) Focusses on effects on spacecraft components. User specifies device geometry Input: measured SEP spectrum – can produce doses for specific events Now being extended to heavy ions

SPARX model Marsh et al, 2015 Fully 3D SEP transport model Triggered by automated detection of a solar eruptive event COMESEP Alert System

SPARX output E20 W20 W60 E>10 MeV E>60 MeV Flux profile vs time Peak flux Time of maximum flux Event duration Marsh et al, 2015

Radiation module As an initial step, calculate effective doses from protons using conversion coefficients provided by ICRP ICRP,

Conclusions Derivation of radiation doses from SEPs requires accurate spectral information over a wide energy range Unshielded radiation doses to humans in interplanetary space can be calculated by means of conversion coefficients A number of efforts on converting output parameters of physics models into impact are underway

SPARX output t = 1 hr t = 24 hr t = 48 hr t = 72 hr Marsh et al, 2015