This document provides a high-level overview of space radiation environments, focusing on the near-Earth region. It discusses various radiation sources like the sun, cosmic rays, and trapped particles in Earth's magnetic field. Key concepts covered include the Van Allen belts, South Atlantic Anomaly, effects of solar activity, and differences between low Earth orbit and other orbits. Standard models and ongoing uncertainties are also addressed. The presentation aims to simplify this complex topic while acknowledging limitations in current understanding.

1. Space Radiation
Environment*
*Terms & conditions apply
A limited introduction with focus on the near-Earth volume
2017-03-03 – v.3
Timo A. Stein, UiO / IDEAS

2. Disclaimer
• The space environment is complex. This presentation is greatly simplified.
• Radiation is a broad term. Here we mean: energetic particles (>100 keV),
gammas / X-rays only covered as secondaries. Weakly interactive particles
are not covered e.g. neutrinos. Focus on stuff that can affect modern
electronics and human spaceflight.
• Space is large. We focus on our heliosphere.
• Radiation dose is not covered.
• This subject is subject of on-going research. Things will change.
• Presentations often contain errors. If you find one let me know.
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3. Outline
• Take-home slides
• Radiation Environments:
• Solar System
• Earth
• Atmospheric and Ground
• Jupiter
• ECSS Standard
• Q&A
It’s a bit complicated! But don’t worry.
Remotely-related infographic. Image credit: NASA
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4. Radiation Environment: Overview
Space* Radiation Environment
*: here it really means our solar system.
Trapped Particles** (Rad. Belts)
**: only applicable to planets with magnetic field.
Protons (< 100x
MeV)
Electrons
(< 10x MeV)
Heavier Ions
(< 100x MeV)
Transient Population
Galactic Cosmic
Rays
(GCR, < 1 TeV): HZE
ions Z=1-92;
continuous backgr.;
anticorr. with solar
activity.
Solar Energetic
Particle Events
(< 1 GeV): CMEs,
Flares; Short-term,
High flux
electrons || Z=1-2+.
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5. Radiation Environment: Sources
• (Extra-)Galactic Cosmic Rays from
outside the solar system (super
novae, quasars, …)
• Sun (Flares, Coronal Mass
Ejections, Solar Wind)
• High-Altitude Nuclear Testing
(hopefully obsolete – not covered)
• Albedo secondaries e.g. neutrons
from Earth (not covered)
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Crab nebula; Image credit: NASA / ESA

6. Radiation Environment: Parameter Space
• Time (11 year solar cycle, solar
rotation, …)
• Location (orbit type, SAA, …)
• Particle Species
• Particle Energy
• Direction (East-West anomaly, …)
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Image credit: NASA

7. Radiation Environment: Model issue
Model issues:
• based on incomplete data,
• shall predict complex environment,
• dynamics are not fully understood,
• and sporadic events occur.
Even “nowcasting” is hard. Order of magnitude uncertainty
common. Space weather forecasting is premature. Forecasting
needed to protect modern space infrastructure / plan missions.
Env. knowledge -> shielding -> weight -> cost.
Different models fit best depending on orbit and question asked.
Technology changes and hence the models relevance / availability.
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Image credit: REPT team;
JHU/APL, NASA.

8. Some more details.
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9. Radiation Environment: Planetary Interlude
• Trapped particle belts are caused by planetary magnetic fields
(Lorentz force).
• Planets without mag. field:
• Mars
• Venus
• Planets with mag. field:
• Mercury (weak)
• Earth (medium, 31 µT)
• Jupiter (strong, 428 µT)
• Saturn (medium)
• Uranus (medium)
• Neptune (medium) Image credit: Thomson Higher Education
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10. Radiation Environment: Earth Orbit
Van Allan Belts - Principle
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Source: Nick Strobel's Astronomy Notes.
http://www.astronomynotes.com/solarsys/s7.htm#
Image credit: NASA
Image credit: Encyclopaedia Britannica

11. Radiation Environment: Earth Orbit
Van Allan Belts - Structure
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Image credit: GA Tech
http://www.propagation.gatech.edu/ECE6390/project/Fall2012/Team06/Webpage%20Folder/Webpage%20Folder/riskmitigation.html

12. Radiation Environment: Earth Orbit
Van Allan Belts
– Spectra / Temp. Variation
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Image credit: ESA, ECSS‐E‐ST‐10‐04C.
Belt <-> solar 11 year cycle correlation.
Source: Barth et al., 2003
Electrons
Protons

13. Radiation Environment: Earth Orbit
Van Allan Belts - Dynamics
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Image credit: SAMPEX team, Univ. of Colorado

14. Radiation Environment: Earth Orbit
Van Allan Belts – drastic temporal changes
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Transient event Sept. 2012; Image credit:
NASA / JHU-APL / Univ. of Colorado
Dynamics of Van Allan belts; Image credit: NASA
Goddard/Duberstein; DOI: 10.1002/2015JA021569

15. Radiation Environment: Earth Orbit
South Atlantic Anomaly (SAA)
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Protons (SAA) Electrons (SAA + horns of outer belt)
Note: SAA moves ~0.3 degrees westwards per year. Explained by change in terrestrial magnetic field.
Model data: AP8MIN, AE8MAX

16. Radiation Environment: Earth Orbit
South Atlantic Anomaly (SAA) – Why it matters?
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UOSAT-2 orbit. SSO, Perigee x apogee: 622 x 634 km
Image Credit: ESA / NOAA / NGDC Boulder
ImageCredit:ESA/NASA

17. Radiation Environment: Earth Orbit
South Atlantic Anomaly (SAA) - Explanation
Imagecredit:ThomsonHigherEducation
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Image credit: M. Markovic, CC PD

18. Radiation Environment: Earth Orbit
Galactic Cosmic Rays
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Image credit: NASA?
Image credit: Uni. Of Wisc.
Image credit: PDG 2014 Booklet.

19. Radiation Environment: Earth Orbit
Solar Events
Flares (mainly electrons)
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Image credit: NASA
Image credit: SOHO, NASA/ESA

20. Radiation Environment: Earth Orbit
Solar Events
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Coronal Mass Ejection (CME; protons, electrons, ions)
Image credit: NASA
Image credit: NASA

21. Radiation Environment: Earth Orbit
Solar Events
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Solar Particle Event (SPE) – flare or CME emitting large particle amounts
IMP-8 data (SPE = spikes); Note: CNO ions, not protons are shown here.
Anticorrelation GCR/Sunspot number ~ solar wind; Source: Barth et al., 2003
Image credit:
SOHO, NASA/ESA
Massive
Bastille Day Flare
July 14, 2000

22. Radiation Environment: Earth Orbit
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Image credit: Geo Swan, Wiki Commons
Source: Civil Air Patrol USA.
http://www.cap-ny153.org/satellites.htm

23. Radiation Environment: Orbits
• LEO - Low Earth Orbit – low inclination (+/- 65 deg.):
• Inner belt, SAA, Albedo neutrons (low altitude)
• LEO – polar / sun-synchronous orbit SSO (> 80 deg.):
• Inner belt, Outer Belt horns, SAA, GCR / SEP
• MEO – Medium Earth Orbit:
• Outer belt, GCR / SEP (dep. on inclination)
• HEO (e.g. GTO):
• Both belts (dep. on inclination), GCR / SEP
• GEO:
• GCR / SEP, Outer belt
• Interplanetary:
• mission-specific ~ GCR / SEP + planetary flyby / local env.
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Source:CivilAirPatrolUSA.
http://www.cap-ny153.org/satellites.htm

24. Radiation Environment: Earth – Atmosphere
• Atmospheric rad. environment
dominated by secondary particles,
peak ~ 20 km (Pfotzer maximum)
• Primary causes cascade, known as
particle shower.
• Creates multitude of secondaries:
• EM: gammas, electrons
• Hard component: pions, muons
• Nucleonic: protons, neutrons
• Main source of LEO neutrons
(albedo neutrons)
• Affects aviation (polar routes).
• Latitude important: geomagnetic
cut-off.
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Image source: Barth et al., 2003

25. Radiation Environment: Earth – Atmosphere
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Cosmic rays
discovered by Victor Hess
using balloon-borne
measurements
Image from 1911.
Nobel Prize in Physics 1936
with Anderson
Image credit: NY TimesHess 1912 data,
Image credit: Wiki Commons

26. Radiation Environment: Earth – Atmosphere
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Image credit: CPT-SCOPE team
Example: Stratospheric charged particle measurements aboard BEXUS 20, Oct. 2015,
from Kiruna Sweden using the CPT-SCOPE instrument.

27. Radiation Environment: Earth – Ground
• Secondaries peak at
Pfotzer maximum (20 km).
• Particle flux decreases
steadily due to
atmospheric attenuation.
• Ground dominated by
neutrons, and energetic
muons.
2017-03-03 27Image credit: OK State University, USA.

28. Radiation Environment: Earth – Ground
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Image credit: IBM.

29. Radiation Environment: Jupiter
• Toughest radiation environment
around Jupiter
• Largest object in the solar system
(Jupiter’s magnetosphere)
• Strong aurora; Interaction of field
lines with its moons (Io).
• Jovian RF (electron) synchrotron
radiation easily detected from
Earth
Image credit: NASA
Image credit: NASA
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30. Radiation Environment: Jupiter
• RF emission due to trapped electrons (inner belts).
Image credit: NASA
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31. Radiation Environment: Jupiter - relevance
• Relevant env. to evaluate existing models, req.
-> Major science missions to study Jovian system.
JUNOmission,Imagecredit:NASA
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JUICE mission, Image credit: ESA
RADEM@JUICE, Image credit: Efacec
Ready for Jupiter: rad-hard IC VATA466

32. Radiation Environment: Standard
• European ECSS Standard ECSS-E-ST-10-04C – Space engineering: Space
Environment, 2008: Background knowledge, defines models, provides tables
and references. Applicable for all ESA missions.
• NB: Covers entire space environment, not limited to energetic particles.
• Other standards (MIL, ISO) not covered.
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33. Selected references
• Article: J. L. Barth, C. S. Dyer and E. G. Stassinopoulos, "Space, atmospheric, and
terrestrial radiation environments," in IEEE Transactions on Nuclear Science, vol.
50, no. 3, pp. 466-482, June 2003. DOI: 10.1109/TNS.2003.813131. Cf. DOI:
10.1201/9781420084320-c28.
• Standard: ECSS-E-ST-10-04C – Space engineering: Space Environment, 2008
(selected chapters). URL: http://ecss.nl/standard/ecss-e-st-10-04c-space-
environment/
• Book: Fortescue, Peter, Graham Swinerd, and John Stark, eds. Spacecraft systems
engineering. John Wiley & Sons, 2011.
• SPENVIS background reading:
https://www.spenvis.oma.be/help/background/traprad/traprad.html
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34. Last slide
Thanks for your attention.
Q&A
Timo A. Stein, UiO / IDEAS
e-mail: timo.stein [at] ideas.no
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