UPDATE OF THE ESP MODEL FOR SOLAR PROTON RISK ASSESSMENT*

M.A. Xapsos1, C. Stauffer2, G.B. Gee2, J.L. Barth1, E.G. Stassinopoulos1

and R.E. McGuire1

1NASA Goddard Space Flight Center, Greenbelt, MD 207712SGT Inc., Greenbelt, MD 20770

*Supported by the NASA SEE Program

OUTLINE

• Background on Solar Particle Models for Cumulative Fluence• Results

Construction of an Integrated Data Set of solar proton data from IMP and GOES series of satellites

Inclusion of solar minimum time period Extension of statistical model to higher energies

• Summary

SOLAR PROTON MODELS

King and

Stassinopoulos

IMP Solar Max 10 – 100 MeV

JPL IMP and OGO Solar Max 1 – 60 MeV

ESP IMP and GOES Solar Max 1 – 100 MeV

(extrap. to 300)

Model: Data*: Time Period: Energy Range:

* Data from different instruments evaluated independently

CONSTRUCTION OF ANINTEGRATED DATA SET (IDS)

• The measurements made by IMP and GOES instruments are to a large extent complementary IMP-8 GME Instrument

Data has outstanding energy resolution (30 energy bins ranging from 0.88 to 485 MeV)

Low detector noise levels Detectors saturate at high fluxes

GOES Instruments Provide 10 energy bins ranging from 0.6 to 700 MeV Relatively high noise levels, especially at high energy Performs very well at high flux rates

• Integrating these features together produces a better overall data base.

Integrated Data – October 19, 1989 Event

10/1

9/19

89

10/2

1/19

89

10/2

3/19

89

10/2

5/19

89

10/2

7/19

89

10/2

9/19

89

10/3

1/19

89

11/2

/198

9

11/4

/198

9

11/6

/198

9

11/8

/198

9

11/1

0/19

89

11/1

2/19

89

Date & Time

10-6

10-5

10-4

10-3

10-2

10-1

100

101

Dif

fere

nti

al F

lux

(cm

-2s-1

sr-1

MeV

-1)

GOES-7 SEMIMP-8 GME

121-154 MeV Protons

Fluence-Energy SpectraOctober 19, 1989 Event

100 101 102 103

Threshold Energy (MeV)

106

107

108

109

1010

Inte

gra

l Flu

enc

e (c

m-2

sr-1

)

IDS (This Work)GOES-7GOES-6

SOLAR CYCLE DEPENDENCE

• Solar activity levels vary substantially for solar max use statistical model, e.g. King, JPL, ESP

• Solar min activity level is low and reasonably constant model as low “background” activity, always present

Model Solar Minimum Flux Levels

10-1 100 101 102 103

Threshold Energy (MeV)

104

105

106

107

108

109

1010

1011

Inte

gra

l Flu

ence

Per

Yea

r (c

m-2

yr-1

)

Worst Solar Min YearWorst Solar Min PeriodAverage Solar Min YearAverage Solar Max Year

Models for Solar Maximum

10-1 100 101 102 103

Threshold Energy (MeV)

107

108

109

1010

1011

1012

Inte

gra

l Flu

ence

(cm

-2)

ESPJPL91King/StassinopoulosThis Work

2 Years Solar Max

Confidence = 90 %

Model Solar Cycle Dependence

0 1 2 3 4 5 6 7 8 9 10 11 12

Year Number

106

107

108

109

1010

Cu

mu

lati

ve F

lue

nce

(cm

-2)

Solar MinSolar Max

> 107 MeV ProtonsConfidence = 90%

SUMMARY

• An integrated data set of IMP and GOES solar proton data has been developed Used to extend the model energy range out to 327 MeV Used to model the solar minimum time period, thus giving a

complete solar cycle description

• Generally during solar minimum: Event frequencies are smaller Event magnitudes are smaller Energy spectra are softer

• Also nearly finished: Model for 1 to 100 MeV/nucleon alpha particles based on IMP and

GOES data Model for elements C thru Fe (~10 to ~100 MeV/nucleon) based on

ACE data