Solar Particle Effects in Aircrew Dosimetry

Solar Particle Effects in Aircrew Dosimetry Graeme Taylor Neutron Measurement Workshop 26 th October 2006 1

Presentation Overview Overview of aircrew exposure to cosmic radiation NPL s involvement in aircrew dosimetry The origins of solar particle events (SPEs) The dosimetry of SPEs NPL s involvement in measuring SPE doses 2

In-Flight Exposure to Radiation Air crew average occupational exposure: * Short haul: ~2 msv/y * Long haul: ~4 msv/y (average UK background: 2.2 msv/y) * Average nuclear worker: <1 msv/y Since May 2000 airlines in the EU must assess the radiation exposure of air crew 3

Air Crew Exposure Studies CAA / MSSL / NPL / VAA Collaborative Partnership 2000-2004 Objectives: Fly detectors (TEPCs) on commercial aircraft; Compare radiation dose measurements with predictions from computer codes used by airlines, e.g. CARI, EPCARD, SIEVERT 4

Global Dose Rate Map The Space Weather Multimedia CD ROM http://www.df5ai.net/articlesdl/spaceweathercd/spaceweathercd.html 5 0.25

Performance of CARI 6 vs TEPC Mmts for ANZ Routes 35 30 C6.E = (-0.13 = (-0.13 +/- 0.33) +/-0.33) + (1.154 0.023)*TEPC.H + (1.154 +/-0.023)*TEPC.H 25 CARI6 E (usv) 20 15 10 5 6 0 0 5 10 15 20 25 30 35 TEPC H*(10) (usv) ANZ

Comparison of Codes with TEPC Measurements Ambient Dose Equivalent (µsv) Flight Flight TEPC CARI-6 SIEVERT EPCARD Code Lon-S/H 17180100 45.7 36.5 52.9 46.5 Lon-JFK 18190100 35.9 31.6 38.3 38.8 Lon-HK 14150700 37.8 33.4 47.3 39.7 HK-Lon 15160700 40.2 33.2 48.3 46.1 Lon-LA 16170700 40.2 42.6 53.6 51.5 LA-Lon 17170700 37.3 34.4 47.6 46.6 Accuracy < 10% 10% - 20% 20% - 30% >30% 7

The Solar Cycle and Atmospheric Radiation Levels The Space Weather Multimedia CD ROM http://www.df5ai.net/articlesdl/spaceweathercd/spaceweathercd.html Ground-based Cosmic Ray Monitor #Sunspots 8

The Sun s Magnetic Field Source/Credits: ESA / NASA 9

Quiet Sun v Active Sun Source/Credits: Solar & Heliospheric Observatory (SOHO). SOHO is a project of international cooperation between ESA and NASA 10

Bastille Day Event July 14 th 2000 Source/Credits: Solar & Heliospheric Observatory (SOHO). SOHO is a project of international cooperation between ESA and NASA EIT (Soft X-rays) LASCO C2 & C3 (White light) 11

Disruption of Earth s Magnetic Field Source/Credits: ESA / NASA 12

Issues with CR Dose Predictions Factors Underlying GCR Dose Prediction Galactic Cosmic Ray field is reasonably constant Modulating effects of Solar Activity reasonably well understood Plenty of measurements for comparison Factors Underlying SPE Dose Prediction SPE fields vary widely Modulation effects of Solar Activity unpredictable Very few measurements for comparison 13

GCR v SPE Spectra From: Advances in Space Research, Vol. 32, pp. 81-93, 2003. CALCULATIONS AND OBSERVATIONS OF SOLAR PARTICLE ENHANCEMENTS TO THE RADIATION ENVIRONMENT AT AIRCRAFT ALTITUDES C.S. Dyer, F. Lei, S. N. Clucas, D. F. Smart, M. A. Shea 14

Time-Dependence of SPE Spectra From: Advances in Space Research, Vol. 32, pp. 81-93, 2003. CALCULATIONS AND OBSERVATIONS OF SOLAR PARTICLE ENHANCEMENTS TO THE RADIATION ENVIRONMENT AT AIRCRAFT ALTITUDES C.S. Dyer, F. Lei, S. N. Clucas, D. F. Smart, M. A. Shea 15

Exposure Calculations for Solar Particle Events 10000 1000 100 10 1 2 3 4 5 8 10 11 13 17 19 20 22 23 27 30 31 38 39 41 42 43 44 45 47 48 52 55 59 60 61 Estimated Dose Equivalent (usv) Lantos & Fuller Ground Level Event # Worst-case exposure for typical CDG LAX flight 16

Exposure Calculations for Solar Particle Events 10000 1000 100 10 1 2 3 4 5 8 10 11 13 17 19 20 22 23 27 30 31 38 39 41 42 43 44 45 47 48 52 55 59 60 61 Estimated Dose Equivalent (usv) Lantos & Fuller Dyer et al. (LHR-LAX, FL 390) Ground Level Event # 17

27OCT03 28OCT03 29OCT03 30OCT03 31OCT03 01NOV03 02NOV03 03NOV03 04NOV03 05NOV03 31OCT03 30OCT03 29OCT03 28OCT03 27OCT03 05NOV03 04NOV03 03NOV03 02NOV03 01NOV03 Previous Attempts to Measure SPE doses TEPC Count Rate 18 Date CLIMAX GLM GOES 10 Satellite FOCT2000.ORG

27OCT03 28OCT03 29OCT03 30OCT03 31OCT03 01NOV03 02NOV03 03NOV03 04NOV03 05NOV03 31OCT03 30OCT03 29OCT03 28OCT03 27OCT03 05NOV03 04NOV03 03NOV03 02NOV03 01NOV03 Previous Attempts to Measure SPE doses TEPC Count Rate 19 Date CLIMAX GLM GOES 10 Satellite FOCT2000.ORG

27OCT03 28OCT03 29OCT03 30OCT03 31OCT03 01NOV03 02NOV03 03NOV03 04NOV03 05NOV03 31OCT03 30OCT03 29OCT03 28OCT03 27OCT03 05NOV03 04NOV03 03NOV03 02NOV03 01NOV03 Previous Attempts to Measure SPE doses TEPC Count Rate 20 Date CLIMAX GLM GOES 10 Satellite Moral: Never put all your eggs in one basket! FOCT2000.ORG

FlareWatch Aim: To fly small, robust instruments (THERMO EPD-N2s) on multiple aircraft Partners: BA (probably!) Launch: Spring 2007 (?) 21

Summary SPEs - Usually caused by Coronal Mass Ejections (often associated with Solar Flares). CMEs - Massive bursts of particles catapulted into space by magnetic whiplash Not a problem unless CME trajectory results in a collision with the Earth Not usually as energetic (i.e. penetrating) as GCR, but much higher fluences (x10 5 more) GLEs - Instantaneous dose rates can increase 100-fold or more at aircraft altitudes Associated magnetic storms can alter local earth potentials (Canadian blackouts, 1859 event!) 22

Solar Particle Effects in Aircrew Dosimetry Graeme Taylor Neutron Measurement Workshop 26 th October 2006 23

Variation in Neutron Spectrum with Proton Energy 2.0x10-7 Proton-Induced Neutron Spectra at an Atmospheric Depth of 200 g.cm -2 Group Fluence per Source Proton 1.8x10-7 1.6x10-7 1.4x10-7 1.2x10-7 1.0x10-7 8.0x10-8 6.0x10-8 4.0x10-8 2.0x10-8 100 MeV 200 MeV 300 MeV 400 MeV 500 MeV 600 MeV 700 MeV 800 MeV 800 MeV 1 GeV 24 0.0 10-1 10 0 10 1 10 2 10 3 Neutron Energy (MeV) MCX_A T M2.ORG

Variation in Photon Spectrum with Proton Energy Proton-Induced Photon Spectra at an Atmospheric Depth of 200 g.cm -2 Group Fluence per Source Proton 2.5x10-7 2.0x10-7 1.5x10-7 1.0x10-7 5.0x10-8 100 MeV 200 MeV 300 MeV 400 MeV 500 MeV 600 MeV 700 MeV 800 MeV 800 MeV 1 GeV 25 0.0 10-2 10-1 10 0 10 1 Photon Energy (MeV) MCX_AT M3.ORG

The Solar Cycle # Sunspots 22 Cycles in 242 years: 11 years per cycle 26

Summary Air crew have higher occupational radiation exposures than typical nuclear workers The exact exposure depends on altitude, latitude and duration of a given flight, as well as the solar activity NPL has collaborated in a massive in-flight measurement programme to demonstrate that software used to calculate crew doses performs reasonably well (long-term) Further Work under way in the area, via collaborations with MSSL and SELEX (TEPC development) BA ( Flarewatch solar particle event monitoring) 27

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Typical Route Doses for Solar Max (2000) 70 Route Doses for 83 Flights with Original TEPC LHS Outward RHS Return 65 60 55 50 45 40 35 30 25 20 15 Measured Dose Equivalent (µsv) Measured Dose Equivalent (usv) Boston Miami Tokyo New York Athens Los Angeles J'burg Hong Kong Shanhai Orlando Las Vegas Chicago San Fransisco 31 FLT MEAN1.ORG 10 5 Destination

Chicago San Fransisco Mean Quality Factors 2.5 Quality Factors for 83 Flights with Original TEPC 2.4 2.3 2.2 2.1 2.0 1.9 1.8 1.7 Hong Kong Athens Los Angeles Tokyo New York Miami Boston Orlando Las Vegas Shanhai J'burg 32 FLTMEAN1.ORG LHS Outward RHS Return Q-bar Destination

0 Measuring Cosmic Ray Doses at Aircraft Altitudes Questions? Credits The Space Weather Multimedia CD ROM Animations: ESA / NASA Images: The Space Weather Multimedia CD ROM http://www.df5ai.net/articlesdl/spaceweathercd/spaceweathercd.html Altitude (km) Pres (m #Sunsp 33