1

The QinetiQ Atmospheric Radiation Model and Solar Particle Events

Clive Dyer, Fan Lei, Alex Hands, Peter TruscottSpace DivisionQinetiQ, Farnborough, UK

Paper presented at The Third European Space Weather Week, Brussels, 13-17 November 2006

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An introduction to QARM

• An engineering model of the high energy radiation in the atmosphere – p, n, e, , , spectrum, flux at a given location and time.– As a function of zenith angle.

• The model is based on the use of response matrix of the atmosphere to energetic particle incidence.

• It can be used for both SEE studies and aircrew radiation dose calculations.

• First reported at NSREC 2004 and released in the same year.

• Extensively validated against flight data.

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Components of QARM• Models of the Cosmic ray radiation:

– B&O’N model, MSU model, QinetiQ model.

• Solar energetic protons

– Individual proton spectra for GLEs.

– Need neutron monitor & space data

• Rigidity cut-off code

– MAGNETOCOSMICS/GEANT4

• Response Matrices of atmosphere to energetic particle

– Atmosphere Model: MSES90, NRLMSES2001

– Particle Transport codes: MCNPX, FLUKA, GEANT4

+

Incident particle spectra at top of the atmosphere

Response matricesfor secondary production and distribution

Model for cosmic rays

e.g. CREME96

Model for Solarprotons

e.g. JPL91

Model of the Atmosphere

e.g. MSISE90

Predictions: energy, directional distributions of

secondaries

Inputs: time, location, geomagnetic condition

Rigidity calculation tool. e.g. MAGCOS

GLE SEP spectra

and userdefined spectra

protons

Particle transport code: e.g. Geant4,FLUKA, MCNPX

+

Incident particle spectra at top of the atmosphere

Response matricesfor secondary production and distribution

Model for cosmic rays

e.g. CREME96

Model for Solarprotons

e.g. JPL91

Model of the Atmosphere

e.g. MSISE90

Predictions: energy, directional distributions of

secondaries

Inputs: time, location, geomagnetic condition

Rigidity calculation tool. e.g. MAGCOS

GLE SEP spectra

and userdefined spectra

protons

Particle transport code: e.g. Geant4,FLUKA, MCNPX

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Estimation of Solar Particle Events UsingQARM• QARM model includes 7 solar particle events.

• 4 of these have been validated against CREAM data from Concorde during Sept-Oct 1989.

• Event of 15 April 2001 validated against Spurny-Dachev data for Prague to New York

– Additional data from FRA to DFW being examined.

• Model used to explore environments for various routes, geomagnetic conditions and relative timings of events and flights.

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Solar Particle Event Spectra for Major Ground Level Events (GLE)

• Derived from neutron monitor (NM) and GOES data

• Correspond to the peak spectrum (worst case)

• Event profile according to NM data

1E-13

1E-12

1E-11

1E-10

1E-09

1E-08

1E-07

1E-06

1E-05

0.0001

0.001

0.01

0.1

1

10

100 1000 10000 100000

Proton Energy (MeV)

Pro

tons

.cm

-2 s

-1 M

eV-1

Sr-1

23-Feb-56

29-Sep-89

19-Oct-89

22-Oct-89

24-Oct-89

14-Jul-00

14-Apr-01

Cosmic ray

6The importance of Kp index

CREAM data taken on Concorde during the 24 Oct 1989 event

The geomagnetic conditions were disturbed with Kp =4leading to factor 1.5 increase in dose rate.

7Influence of Actual Route cf Great CircleLHR-JFK 24 October 1989

LHR-JFK 24/10/89

0

20

40

60

80

100

120

0 50 100 150 200

0

0.5

1

1.5

2

2.5

3Actual alt.

Actual dose

GC alt.

GC dose

CREAM data

Actual R

GC R

Concorde route during event of24 October 1989 (Kp = 4).Data from CREAM.Peak dose rate on great circle routewould have been factor 2.5 highercf actual route.

8GLE60 (Kp =3) : PRG-JFK Great Circle vs. Actual Flight path

PRG-JFK 15 April 2001PRG-JFK 15 April 2001

Prague - NY 15/04/01

0

5

10

15

20

25

0 100 200 300 400 500

0

0.5

1

1.5

2

2.5

3

3.5

4

Actual dose

GC dose

Actual alt.

GC alt.

Dachev measurements

Actual R

GC R

Data from Spurny & Dachev

QARM gives reasonable agreementand shows that a small deviationfrom great circle gave factor 2 reduction in peak dose rate.

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LHR to LAX Great Circle Route

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Influence of Solar Particle Eventof 29 Sept 1989on LHR-LAXFlight; Kp=0

Worst case event start is 1 hour after take-off

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Influence of Solar Particle Eventof 15 April 2001on LHR-LAXFlight; Kp=0

Worst case event start is 2 hours after take-off.

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Solar Particle Event Doses for LHR-LAX at 12 km Estimated Using QARM

Event 23 Feb1956

29 Sept1989

19 Oct1989

22 Oct1989

24 Oct1989

14 July2000

15 April2001

W/C EventStart (hrs)

3 1 0 1 1 2 2

Peak DoseRate(mSv/hr)

1.82 0.29 0.022 0.039 0.049 0.013 0.041

RouteDose(mSv)

2.27 1.28 0.12 0.15 0.25 0.031 0.078

Note: Additional to GCR Route Dose of 0.05-0.06 mSvGeomagnetic Conditions Quiet.W/C increase for Sept 89 gives 1.33 mSv for Kp=6Event start measured wrt take-off.

13Sydney to Johannesburg Great Circle Route

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Solar Particle Event Doses for Sydney-Johannesburg at 12 km Estimated Using QARM

Event 23 Feb1956

29 Sept1989

19 Oct1989

22 Oct1989

24 Oct1989

15 April2001

20 Jan2005

W/C EventStart (hrs)

5 2 1 2 2 4 5

Peak DoseRate(mSv/hr)

1.79 0.28 0.020 0.037 0.047 0.040 3.0

RouteDose(mSv)

2.06 1.15 0.11 0.14 0.22 0.073 0.35

Note: Additional to GCR Route Dose of 0.06-0.07 mSvGeomagnetic Conditions Quiet.W/C increase for Sept 89 gives 1.27 mSv for Kp=6Event start measured wrt take-off.Event of 20 Jan 05 very anisotropic. Crude estimate only.

15Polar Great Circle RouteChicago to Beijing

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Influence of solar particle event of

29 Sept 1989 on Chicago to BeijingFlight.Accumulated dose is 1.4 mSv

17Summary

• QARM is an engineering model of atmospheric radiation environment and allows for time variations in GCRs, SPEs and geomagnetic cut-off.

• It has been widely validated and can be applied to radiation effects/protection applications in microelectronics and personnel

• Energetic solar particle event that are seen as GLEs can significantly enhance the radiation field in the atmosphere leading to route doses that can exceed 1 mSv together with high SEE rates (several per flight in key equipment).

• Accurate assessment of the enhanced radiation to a flight requires good knowledge of– The event proton spectrum and its time variation

– The exact geomagnetic conditions

– Detailed flight path (great circle approximations inadequate)

• Sensitivity to flight path implies possibility of radiation reduction.

• Possibility of near real time warning via rapid assimilation of both space and neutron monitor data.

• However solar particle events are far from isotropic – Neutron Monitors provide crucial data

– Accurate dose can be obtained only from real-time onboard monitors

• QARM is available online: qarm.space.qinetiq.com

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Change in cut-off rigidity with geomagnetic activity.Rigidity for Kp= 0 subtracted from that for Kp = 6

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Calculated Neutron Fluxes for Concorde JFK-LHRon 29 Sept 1989 for 2 Geomagnetic Conditions

0

20

40

60

80

100

120

140

160

14:00 14:28 14:57 15:26 15:55 16:24 16:52 17:21 17:50

Date

Ne

utr

on

Flu

x (/

cm2 /s

) &

Ne

utro

n %

Inc

Kp=Actual (2)

Kp=5

CREAM N Flux

Climax %Inc

0

5

10

15

20

14:00 14:28 14:57 15:26 15:55 16:24 16:52 17:21 17:50

Time

H(k

m)

0

500

1000

1500

2000

2500

En

erg

y C

ut-

off

(Me

V)

H(km) Ec (Kp=Actual) Ec (Kp=5)

21GLE42 (Kp =2): JKF-LHR Great Circle vs. Actual Flight path

JFK-LHR 29 September 1989

JFK-LHR 29/09/89

0

50

100

150

200

250

0 50 100 150 200

0

0.5

1

1.5

2

2.5

3

Actual alt.

GC alt.

Actual dose

GC dose

CREAM data

Actual R

GC R

Concorde route during event of29 September 1989 (Kp = 2).Data from CREAM.

Peak dose rate on great circle routewould have been factor 5 highercf actual route.