1. Daniel Matthiä(1)‏, Bernd Heber(2), Matthias Meier(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. Introduction: Dose Rates at Aviation Altitudes
Introduction: Dose Rates at Aviation Altitudes
Radiation exposure is increased at aviation altitudes
Galactic cosmic rays (GCR)
Solar energetic particles (SEP) during Ground level events/enhancements (GLE)

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

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

5. Determination of SEP spectrum
Determination of SEP spectrum
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)‏
Calculate secondary particle fluences at aviation altitudes
Conversion to radiation exposure 5

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

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

8. Results Modeling of Ground Level Events

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

10. Results GLE 70: Calculated Neutron Monitor Count Rates
Results GLE 70: Calculated Neutron Monitor Count Rates 10

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

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

13. Results - GLE70: Dose Rates on High Latitude Flights
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) 13

14. Results - GLE70: Dose Rates on High Latitude Flights
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 14

15. Results – Analysis of GLEs
Results – Analysis of GLEs
Results – Analysis of GLEs
Date
Spectral index
Effective Dose increase
(Flights on the northern hemisphere)
GLE42
Sept. 29th, 1989
3.5-6
Up to 600%
GLE60
April 15th, 2001
Up to 130%
GLE69 (1)
Jan. 20th, 2005
5.5-7
GLE70 (2)
Dec. 13th, 2006
4.5-6
Up to 30%
(1)Matthiä et al., 2009, J. Geophys. Res., 114
(2)Matthiä et al., 2009, Radiat Prot Dosimetry, 136 15
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 dose rates for arbitrary locations and flights
Increases in the total effective dose on northern hemisphere flights between 30% and 600%

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

18. Results Neutron Monitors – Asymptotic Viewing Directions
Results Neutron Monitors – Asymptotic Viewing Directions
Large rigidity
Small rigidity 18

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

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

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

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

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

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

25. “Is the Sun mad at us?”