The Impact of Solar Particle Events on the Radiation Exposure in Aviation

1. The Impact of Solar Particle Events on the Radiation Exposure in Aviation Daniel Matthiä(1)‏, Bernd Heber(2), Matthias Meier(1), Thomas Berger(1), and Günther Reitz(1) (1) Department of Radiation Biology, Institute of Aerospace Medicine, German Aerospace Center (DLR), Germany (2) Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität Kiel, Germany

2. Solar energetic particles (SEP) during Ground level events/enhancements (GLE) Introduction: Dose Rates at Aviation Altitudes Radiation exposure is increased at aviation altitudes Galactic cosmic rays (GCR)

3. Latitudinal dependence (Magnetic shielding) Altitude dependence (Atmospheric shielding) Temporal dependence (Solar modulation) Solar minimum Radiation Exposure (Galactic Cosmic Rays)

4. Ground Level Enhancements (GLE)‏ GLE69 Kiel NM What is the primary particle spectrum? How is the radiation environment affected?

5. Determination of SEP spectrum Calculate secondary particle fluences at aviation altitudes Conversion to radiation exposure Assume spectrum for Solar Energetic Particles at time t Calculate secondary particle fluences and Neutron-Monitor count rates related to GCR and SEP (PLANETOCOSMICS, GEANT4) Compare to measured count rates (~30 stations)‏ Adapt spectrum for SEP (Minimization)‏

6. Primary SEP spectrum Assumption: Power law in rigidity R with spectral index γ

7. Primary SEP spectrum Linear dependence in the angle α with anisotropy parameter b Assumption: Power law in rigidity R with spectral index γ Minimize differences in calculated and measured count rates by adapting the parameters!

8. ResultsModeling of Ground Level Events

9. GLE 70: Neutron Monitor Count Rate Increases Strong increase High anisotropy Slower, delayed increase

10. ResultsGLE 70: Calculated Neutron Monitor Count Rates

11. Results -GLE70: Primary proton spectra Softening of the spectrum Decrease in intensity

12. Results -GLE70: Dose rates at 200g/cm2(≈12km, ≈FL390)‏ Along 25°E Peak values of 4.5 to 5 times GCR background

13. Results -GLE70: Dose Rates on High Latitude Flights Results -GLE70: Dose Rates on High Latitude Flights ‏Frankfurt – Los Angeles (FRA-LAX): North Atlantic route New York to Bejing (JFK-PEK): Polar route On the great circle‏‏ at 200 g/cm2 (≈12km, ≈FL390)

14. Results -GLE70: Dose Rates on High Latitude Flights • ‏At 200 g/cm2 (≈12km, ≈FL390)‏‏ • FRA-LAX: ~120 μSv (~90μSv)‏ • JFK-PEK: ~130 μSv (~100μSv) • ~30% increase above GCR 12km altitude GCR GCR+SEP

15. (1)Matthiä et al., 2009, J. Geophys. Res., 114 (2)Matthiä et al., 2009, Radiat Prot Dosimetry,136 Results –Analysis of GLEs Results –Analysis of GLEs Results –Analysis of GLEs

16. Summary • Transport calculations of GCR and SEP through the magnetosphere and atmosphere • Determination of primary particle spectra during GLEs were derived from Neutron Monitor count rate increases • The model can provide based on NM data: • Temporal evolution of SEP events over several hours • Incident direction • Energy spectrum • Angular distribution • Total effective doses and doserates for arbitrary locations and flights • Increases in the total effective dose on northern hemisphere flights between 30% and 600%

17. Absorbed Dose Equivalent Dose Effective Dose Ambient Dose Equivalent Dosimetric Quantities

18. ResultsNeutron Monitors – Asymptotic Viewing Directions Large rigidity Small rigidity

19. GLE 70: Selected Neutron Monitor Count Rate Increases Strong increase High anisotropy Slower, delayed increase

20. Results -GLE 70 - Primary Proton SpectrumAverage Spectrum December, 13th 2006, 2:40 UTC - 11:35 UTC

21. Results - GLE 70: Parameter of the primary spectrum Intensity at 1GV

22. Results - GLE 70: Parameter of the primary spectrum Spectral parameter

23. Results - GLE 70: Parameter of the primary spectrum Anisotropy parameter

24. Results - GLE 70: Incident direction of the SEP Interplanetary magnetic field (IMF) from ACE

25. “Is the Sun mad at us?”