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Engineering Models for Galactic Cosmic Rays and Solar Protons: Current Status

Engineering Models for Galactic Cosmic Rays and Solar Protons: Current Status. Stephen Gabriel Professor of Aeronautics and Astronautics School of Engineering Sciences University of Southampton England Email : sbg2@soton.ac.uk. Outline.

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Engineering Models for Galactic Cosmic Rays and Solar Protons: Current Status

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  1. Engineering Models for Galactic Cosmic Rays and Solar Protons: Current Status Stephen Gabriel Professor of Aeronautics and Astronautics School of Engineering Sciences University of Southampton England Email : sbg2@soton.ac.uk 3rd SPENVIS USERS WORKSHOP

  2. Outline • Phenomenology : GCRs and Solar Energetic Particle Events(SEPEs) • Requirements on engineering models • Existing Models : GCRs SEPEs • Issues and the future 3rd SPENVIS USERS WORKSHOP

  3. Cosmic Rays: Origins and Acceleration ·     Galactic Cosmic Rays Present consensus: Fermi acceleration by supernova shock- wave remnants ·     Anomalous Cosmic Rays Thought to originate as neutral interstellar gas that drifts into the heliosphere, becomes singly-ionized near the sun and then convected to outer heliosphere where accelerated to higher energies 3rd SPENVIS USERS WORKSHOP

  4. Cosmic Rays: Time Variations 3rd SPENVIS USERS WORKSHOP

  5. Cosmic Rays: Propagation where 3rd SPENVIS USERS WORKSHOP

  6. Cosmic Rays – Energy Spectra Quiet-time energy spectra for the elements H, He, C, N and O measured at 1 AU over the solar minimum period from 1974 to 1978 (from Mewaldt et al., 1984). Note the “anomalous” enhancements in the low-energy spectra of He, N and O. The data are from the Caltech and Chicago experiments on IMP-7 and IMP-8. (from Mewaldt, 1988) 3rd SPENVIS USERS WORKSHOP

  7. Cosmic Rays – Energy Spectra (contd) 3rd SPENVIS USERS WORKSHOP

  8. Cosmic Rays - Composition 3rd SPENVIS USERS WORKSHOP

  9. Solar Protons: Origins and Acceleration (1) Energetic Particle Events at the Sun Current view: Particle acceleration is caused by coronal mass ejection (CME) driven shocks in the corona and interplanetary medium 3rd SPENVIS USERS WORKSHOP

  10. Solar Protons:Origins and Acceleration (2) X -ray events detected by GOES 7 spacecraft in geosynchronous orbit. The vertical lines are hour markers. The left-hand panel shows an impulsive event at about 9:00 UT (Universal Time) on May 3,1992. The right-hand panel shows a gradual event at about 15:45 UT on May 8, 1992. (From Solar-Geophysical Data, Prompt Reports, Number 574-Part 1, June 1992, National Geophysical Data Center, Boulder CO.) 3rd SPENVIS USERS WORKSHOP

  11. Solar Protons: Origins and Acceleration (3) 3rd SPENVIS USERS WORKSHOP

  12. Solar Protons: Propagation (1) Propagation of solar energetic particles. Those propagating along the “favorable path” will be anisotropic at Earth. (From Shea, 1988) 3rd SPENVIS USERS WORKSHOP

  13. Solar Protons: Propagation (2) Longitude distribution of propagation times of solar particles from the flare to the Earth. The various symbols indicate data from different studies. The line is added to guide the eye. (From Smart and Shea, 198,5, and Barouch et al., 1971) 3rd SPENVIS USERS WORKSHOP

  14. Solar Protons: Time Variations Solar Cycle Solar cycle variation of yearly integrated fluences observed at 1 AU (From Feynman et al., 1990) 3rd SPENVIS USERS WORKSHOP

  15. Solar Protons: Energy Spectra Exhibit large range both in fluence and peak flux spectra From R.A. Mewaldt et al, “Solar Particle Energy Spectra during the Large Events of October-Novemeber 2003 qnd January 2005”, 29th International Cosmic Ray Conference Pune (2005) 00, 101-104 3rd SPENVIS USERS WORKSHOP

  16. Solar Protons: Time Variations Event Duration Proton fluxes from two major solar proton events (E > 60 MeV). Data from IMP 8 (T.P Armstrong, personal communication) 3rd SPENVIS USERS WORKSHOP

  17. Solar Protons: Time Variations (cont) From R.A. Mewaldt et al, “Solar Particle Energy Spectra during the Large Events of October-Novemeber 2003 qnd January 2005”, 29th International Cosmic Ray Conference Pune (2005) 00, 101-104 3rd SPENVIS USERS WORKSHOP

  18. Solar Protons: Composition Solar Energetic Particle Abundances From Reames, 1997 3rd SPENVIS USERS WORKSHOP

  19. Annual Proton Fluence vs Sunspot Number 3rd SPENVIS USERS WORKSHOP

  20. Engineering Models : Requirements • For all high energy particle species(electrons, protons and heavy ions): • Flux spectrum ( instantaneous) • Fluence spectrum • Directionality • Spatial dependence • At any time ( including solar cycle variations) • High Velocity Coronal Mass Ejections(CMEs) 3rd SPENVIS USERS WORKSHOP

  21. Important Parameters for Engineering Design • Total Event Fluence • Peak Flux • Duration • Hardness (Spectral Form) • Heavy ion abundance • Propagation • Confidence Level/uncertainty (Design Margins) 3rd SPENVIS USERS WORKSHOP

  22. GCR Models • CREME 96 regarded as the most up-to-date and comprehensive model • CREME96 is an update of the Cosmic Ray Effects on Micro-Electronics code, a widely-used suite of programs for creating numerical models of the ionizing-radiation environment in near-Earth orbits and for evaluating radiation effects in spacecraft. 3rd SPENVIS USERS WORKSHOP

  23. CREME 96 • Has many significant features, including • (1) improved models of the galactic cosmic ray, anomalous cosmic ray, and solar energetic particle components of the near-Earth environment; • (2) improved geomagnetic transmission calculations; • (3) improved nuclear transport routines; • (4) improved single-event upset (SEU) calculation techniques, for both proton-induced and direct-ionization-induced SEUs; and • (5) an easy-to-use graphical interface, with extensive on-line tutorial information. 3rd SPENVIS USERS WORKSHOP

  24. Cosmic Rays: Solar Cycle Modulation CREME 96 3rd SPENVIS USERS WORKSHOP

  25. SEPE models • All current models are statistical/probabilistic in nature • 3 most recent proton models : • JPL – 91 • Xapsos et al • Nymmik(MSU) • Heavy Ion Model : Tylka : PROBABILITY DISTRIBUTIONS OF HIGH-ENERGY SOLAR- HEAVY-ION FLUXES FROM IMP-8: 1973-1996 IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 44, NO. 6, DECEMBER 1997 3rd SPENVIS USERS WORKSHOP

  26. Comparison of 3 Models • Nymmik assumes that the mean event frequency is proportional to the average sunspot number while others assume that there are 7 active years of a solar cycle • JPL models assume a log normal distribution, Nymmik model assumes a power law, Xapsos determines the distribution using maximum entropy ( truncated power law) • JPL model only goes up to >60MeV, MSU model up to 100s of MeV 3rd SPENVIS USERS WORKSHOP

  27. Comparison of 3 Models • JPL model is for fluences only while MSU and Xapsos have peak flux models too • Event definition appears to be different between JPL and MSU models • Different data sets for all three models 3rd SPENVIS USERS WORKSHOP

  28. ESP and JPL-91 comparison Sample spectra of the ESP models for a seven year mission in solar maximum conditions and confidence level 90%: ___ total fluence model; ___ worst case event fluence model; ___ JPL model for the same conditions. 3rd SPENVIS USERS WORKSHOP

  29. Fluence Probability Curve (1) 3rd SPENVIS USERS WORKSHOP

  30. Distribution of Solar Event Fluences (1) 3rd SPENVIS USERS WORKSHOP

  31. Sensitivity of fluence model to the size of the event data set • Rosenqvist and Hilgers1 have shown that the current size of the event data set ( ~ 200 events) can lead to significant errors in the prediction of the fluence probability distribution function • 1 Rosenqvist, L. and Hilgers, A. “Sensitivity of a statistical solar proton fluence model to the size of the event data set”, Geophysical Research Letters, 30, 1865, 2003 3rd SPENVIS USERS WORKSHOP

  32. Geomagnetic Shielding: Simple Theory • During quiet periods, Stormer Theory can be used : • Assumes Earth's magnetic field is dipolar • Gives cut-off rigidity, RC (minimum momentum per unit charge) for a particle arriving from a given direction to reach a given location at the Earth • Useful approximation for lowest value, RCW, which is from magnetic west, is •   RCW = [CScos4] / {r2[1+ (1+ cos3)1/2]2} • where CS a constant, r is distance from dipole centre in earth radii and  is magnetic latitude 3rd SPENVIS USERS WORKSHOP

  33. Geomagnetic Shielding: Störmer Theory (2) Cut-off rigidity in the dipole approximation of the Earth's magnetic field for west, east, and vertical direction as a function of magnetic latitude (from Klecker, 1996) 3rd SPENVIS USERS WORKSHOP

  34. Geomagnetic Shielding: Simple Theory 3rd SPENVIS USERS WORKSHOP

  35. Conclusions   Concentrated on existing engineering models and their inadequacies,ideally what is needed and some of the basic physics Models : Cosmic Rays:CREME 96:    Uses Nymmik's semi-empirical model for solar cycle modulation based on Wolf sunspot number (includes large-scale structure of heliospheric magnetic field) Incorporates multiply-charged ACR component (above ~ 20 MeV/nucleon), from Sampex results ~ 25% error on average for solar modulation and spectra, compared to data 3rd SPENVIS USERS WORKSHOP

  36. Conclusions (contd.)  Geomagnetic Shielding   More data analysis/modelling during active periods to understand cut-off depression/predict transmission (CRÈME 96 combined IGRF and extended Tsyganenko model) Importance of partially-ionised heavy ions (mean-ionic charge ~14 rather than 26) 3rd SPENVIS USERS WORKSHOP

  37. Conclusions (contd.)  Solar Protons • Importance of CMEs and CME-driven shocks • Currently,most generally accepted statistical models are JPL-91 (“The JPL proton fluence model : an update”, Feynman et al, Journal of Atmospheric and Solar-Terrestrial Physics) and ESP(Xapsos) models. 3rd SPENVIS USERS WORKSHOP

  38. Conclusions (contd.)Solar Protons • New ESA model under development: • Data driven models • Must address user needs • Better Radial Scaling needed for missions like Bepi Colombo, Solar Orbiter, Solar Dynamic Observer, Heliospheric Sentinels, STEREO, Mars missions, etc 3rd SPENVIS USERS WORKSHOP

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