Radiation Environment. Efforts at JPL. Dr. Henry Garrett. Jet Propulsion Laboratory 4800 Oak Grove Dr. Pasadena, CA 91109

Transcription

1 Space Modeling Space Radiation Radiation Environment Environment Modeling Efforts Efforts at JPL JPL Dr. Henry Garrett Jet Propulsion Laboratory 4800 Oak Grove Dr. Pasadena, CA Spacecraft Environmental Interactions, Envts (Garrett).ppt 2-1

2 SPACE RADIATION RADIATION ENVIRONMENTS ENVIRONMENTS SUN SEP Models EARTH POES SAA Models Geosynchronous Plasma PLANETS Jupiter Saturn MAN-MADE RPG/RHU 2-2

3 SOLAR PROTON EVENTS-SPACE RAIN 2-3

4 FREQUENCY OF MAJOR SOLAR PROTON EVENTS 2-4

5 JPL SPE Model Updates Purpose of new model is to develop statistical distributions of 3 quantities: -Event fluences: Log-normal distribution -Event durations: Poisson Distribution -Time Intervals between events: Poisson Distribution Event Fluence Can generate a virtual data set based on these three distributions. Spacecraft Environmental Interactions, Time interval between events Duration of events 2-year at 1 AU Envts (Garrett).ppt 2-5

6 JPL SPE Model Updates SPE Model Composition Fraction of missions with fluences > F. This particular example was obtained for a 60-day solar probe mission trajectory with a 1/r2 scaling factor. 2-6

7 JPL SPE Model Updates Publications: - Feynman, J, G. Spitale, J. Wang and S. Gabriel, Interplanetary proton fluence model : JPL 1991, J. Geophys. Res., 98, 13281, Ruzmaikin, A., G. Li, G. Zank, J. Feynman, and I. Jun, The radial dependence of solar energetic particle fluxes, 11th Solar Wind/ SOHO 16: Connecting Sun and Heliosphere, June 11-17, Swimm, R. T., I. Jun, A. Ruzmaikin, J. Feynman, A. J. Tylka, and W. F. Dietrich, Statistics of solar energetic particle events: fluences, durations, and time interval, 36th COSPAR Scientific Assembly, Beijing, China, July 16-23,

8 EARTH TRAPPED RADIATION MODELS Contour plots of > 1MeV electron and >10 MeV proton integral fluxes at Earth. Coordinate system used is geographic at the 0 meridian. Based on AP8 and AE8 solar maximum models. 2-8

9 Why is there a South Atlantic Anomaly? 2-9

10 Long-Term Observations of Trapped High-Energy Protons (L<4) by NOAA Polar Orbiting Environmental Satellites (POES) D. Evans (NOAA), H. Garrett (JPL), I. Jun (JPL), R. Evans (Gibbel Corp.), and J. Chow (Raytheon Corp. SPACECRAFT: ORBIT: PERIOD: NOAA-15, -16, -17 ~840 Km altitude, 98 Incl June 1, 1998 June 30, 2005 ~15 satellite-years INSTRUMENT: Space Environment Monitor (SEM)-2 Omni-directional H+ detectors ENERGY RANGE: >16 MeV, >36 MeV, >70 MeV, >140 MeV COVERAGE: 8-s intervals on 1 lat x 2 long grid N-72.5 S; E 2-10 SEM-2 Omni-Directional Detectors

11 POES Observations of the South Atlantic Anomaly (SAA) P6: >16 MeV 50% P9: >140 MeV Contour Plots of Trapped Protons 95% High radiation region at high latitude, likely due to E>3MeV electrons 50% 95% 2-11

12 POES Observations of the SAA and Nearby Regions (L<4) Low L Region Normalized statistical (percentile) distribution of the particle fluxes at a given energy and at a specified B and L for P6. High L Region POES Model of the SAA and Nearby Regions (L<4) 2-12

13 Summary of POES Long-term Statistics for Low-Altitude, High-Energy Trapped H+ Environment SUMMARY: - Energetic H+ fluxes vary by only ~2 between 10% and 99% levels in SAA. - Little or no association between H+ intensities and SEP events in SAA. - Proton intensities at POES altitudes in SAA primarily governed by local pitch-angle extent over which trapped protons access satellite. - Highly variable secondary region of enhanced P6 responses at L>3.0 -~1000's between10%-99%. Sensor responses at 90% and above believed to be dominated by episodes of high intensity, >3 MeV electrons ( ). - Data set forms extensive source of information for studying long-term near-earth trapped proton environment as a function of solar cycle and magnetic activity and for evaluating role of SEP events. 2-13

14 JPL Geosynchronous Plasma Models 2-14

15 Two Maxwellian Plasma Model Approach 2-15

16 THE GEOSYNCHRONOUS PLASMA ENVIRONMENT MODEL STATISTICAL DISTRIBUTIONS OF KEY GEOSYNCHRONOUS PARAMETERS LOCAL TIME/Kp VARIATIONS FOR KEY GEOYSNCHRONOUS PLASMA PARAMETERS 2-16

17 Jupiter 2-17

18 Jupiter 2-18

19 Jupiter s Magnetic Field X 104 = 2-19

20 JUPITER S LOW ENERGY PLASMA ENVIRONMENT 2-20

21 DIVINE/GIRE JOVIAN TRAPPED RADIATION MODELS Contour plots of >1 MeV electron and >10 MeV proton integral fluxes at Jupiter. Coordinate system used is jovi-centric. Models are based on Divine/GIRE models. Meridian is for System III 110 W. 2-21

22 DIVINE HIGH ENERGY ELECTRON MODEL 2-22

23 COMPARISONS BETWEEN JOVIAN AND TERRESTRIAL RADIATION SPECTRA 2-23 COURTESY A. JOHNSTON

24 Saturn 2-24

25 Saturn 2-25

26 HIGH ENERGY ELECTRON AND PROTON FLUXES AT SATURN (DIVINE/SATRAD) 2-26

27 DIVINE/SATRAD SATURN TRAPPED RADIATION MODELS o West Longitude = R s Contour plots of >1 MeV electron and >10 MeV proton integral fluxes at Saturn. Coordinate system used is Saturn-centric. Models are based on Divine/SATRAD models. Meridian is for 0 W. 2-27

28 Earth TRAPPED RADIATION BELTS Jupiter o West Longitude = 0 Saturn R s

29 MAN-MADE ENVIRONMENTS 2-29

30 GALILEO RADIOISOTOPE SOURCES General Purpose Heat Source Radioisotope Thermoelectric Generator Lightweight Radioisotope Heater Unit 2-30

31 GALILEO RTG NORMALIZED AND NEUTRON FLUXES 2-31

32 GALILEO RTG AND NEUTRON FLUXES VS DISTANCES 2-32

33 GALILEO RADIOISOTOPE THERMOELECTRIC GENERATOR ISODOSE-ISOFLUX CONTOURS 2-33