NASA Technical Reports Server (NTRS) 20160006862: Introduction to Space Radiation

3.2 MB·English

by  NASA Technical Reports Server (NTRS)

HematologicalCancerWorkingGroup
On-LineSeminar
ThursdayJanuary22,2015
INTRODUCTION TO SPACE RADIATION
John Norbury
NASALangleyResearchCenter,Hampton,Virginia,USA
JOHNNORBURY (NASALANGLEY) SPACERADIATION WEDNESDAYJUNE11,2014 1/70
OUTLINE
1 3 SOURCES OF SPACE RADIATION
2 RADIATION & DOSE
3 NUCLEAR & PARTICLE PHYSICS & TRANSPORT
4 MOON, MARS, JUPITER, SATURN
5 CONCLUSIONS
JOHNNORBURY (NASALANGLEY) SPACERADIATION WEDNESDAYJUNE11,2014 2/70
3 SOURCES OF SPACE RADIATION

3 sources of space radiation
Geo
SPE
GCR
[https://oltaris.larc.nasa.gov]
JOHNNORBURY (NASALANGLEY) SPACERADIATION WEDNESDAYJUNE11,2014 3/70
GALACTIC COSMIC RAYS (GCR) - DISCOVERY
It all began with a mystery
surrounding the continuous &
uncontrollable leakage of electrical
charge from a well insulated
charged gold leaf electroscope.
Mystery unexplained since Henry
Coulomb noticed in 1785, that
charged metal sphere suspended
by insulated silk thread did not
retain charge.
[http://www.school-for-champions.com/experiments/]
JOHNNORBURY (NASALANGLEY) SPACERADIATION WEDNESDAYJUNE11,2014 4/70
Galactic Cosmic Rays - Discovery
GALACTIC COSMIC RAYS (GCR) - DISCOVERY
•  IInn eeaarrllyy ddaayyss eelleeccttrroossccooppeess &&
eelleeccttrroommeetteerrss aallssoo uusseedd ttoo ssttuuddyy
xx--rraayyss,, rraaddiiooaaccttiivviittyy,, eettcc..
X-rays & radioactive emanations
•  x-rays & radioactive emanations ionize
ionize gases
gases
Strong sources of radiation cause
•  Strong sources of radiation cause
leaves in electroscope to come
leaves in electroscope to come
together
together (after electroscope initially charged)
(afterelectroscopeinitiallycharged)
•  Strength of radiation can be measured
Strength of radiation can be
by how quickly leaves come together
measured by how quickly leaves
come together
[Closeetal.,Theparticleexplosion,OxfordUniv.Press,Oxford,1994]
JOHNNORBURY (NASALANGLEY) SPACERADIATION WEDNESDAYJUNE11,2014 5/70
GALACTIC COSMIC RAYS (GCR) - DISCOVERY

Galactic Cosmic Rays - Discovery
Researchers found trouble:
Turn of all Crookes tubes,
•  Researchers found trouble:
remove all radiation sources,
•  turn of all Crookes tubes, remove all
remove light
radiation sources, remove light
• Stsitlillle elleeccttrroossccooppee lelaevaevse fsallf atollgether
together
[Lederman&Schramm,Fromquarkstothecosmos,
Freeman,NewYork,1989]
•  At end of C19 Wilson connected this to ionization of
End of C19 Wilson connected this to ionization of surrounding air
surrounding air.
W•  itWhitdhi sdcisocvoeveryryo off rraaddiiooaacctitviivtyit y& &finfidnindgi nthgatt heaartthe aitsrethlf citosnetlafinceodn tained
minmuinteutter atrcaecesso off rraaddiiooaacctitvivee mmataertiearlsia, list ,wiatsw maisstamkiesntlayk tehonulyghtht ought
that source of ionization of air was this radioactive material of
that source of ionization of air was this radioactive material of
earth.
earth.
JOHNNORBURY (NASALANGLEY) SPACERADIATION WEDNESDAYJUNE11,2014 6/70
GALACTIC COSMIC RAYS (GCR) - DISCOVERY
Implied that leakage rate (rateatwhichleaves
cometogether) should be smaller at higher
altitudes
1910 Father Thomas Wulf took electroscope to
top of Eiffel tower
Observed 64% drop in leakage rate
But expected much more reduction
(radiation should be absorbed in air)
Deduced that radiation from ground
(gradually decreasing with height)
competing with radiation coming down
through atmosphere
Obvious thing was to go to greater heights
[Norbury,2010]
(Wulf did not!)
JOHNNORBURY (NASALANGLEY) SPACERADIATION WEDNESDAYJUNE11,2014 7/70
Galactic Cosmic Rays - Discovery
GALACTIC COSMIC RAYS (GCR) - DISCOVERY
Starting in 1911, Victor Hess (Austrian)
was firSstta rtotin pgrinod19u1c1e, VdiectcoirsHiveess r(eAsuuslttrsia n) was
from bfiarlsltotoonp rfolidguhcetsd ienc iwsivheicrehs uhlets from balloon
ascendflieghdt swinithw heiclehchteroasscceonpdeeds with
electroscopes
Radiation first decreased as balloons
•  radiation first decreased as balloons went up
went up
•  but by 5,000 ft. radiation was more intense
than at sBeuat bleyv5e,l0 00 ft. radiation was more
•  by 17,50in0t eftn.s readthiaatnioant isnecareleavseeld several
times By 17,500 ft. radiation increased
•  Hess hyspeovtehreaslitzimede s“extra-terrestrial source
of radiation”
Hess hypothesized “extra-terrestrial
•  named Cosmic Radiation by Millikan in 1925
source of radiation”
Named Cosmic Radiation by Millikan in
1925
[Friedlander,Nature483,400,2012]
JOHNNORBURY (NASALANGLEY) SPACERADIATION WEDNESDAYJUNE11,2014 8/70
6
littlesubsequentnucleartransformations.Thereisalsoapri- ferent. Nevertheless,atsuchanaccelerator,thenonthermal
maryCRelectroncomponentandatGeVenergiesitsflux powerlawdistributionoftheCRsshouldgrowoutofthe
is two orders of magnitude below that for protons. Most thermaldistributionsomewhereabovethegasthermalen-
impressively,theall-particleenergyspectrumextendsover ergy. ThiscanbeseeninFig. 5whichshowsananalytical
morethan11ordersofmagnitudeinenergy. Itistheproto- calculationofdiffusiveparticleaccelerationatashockwave.
typeofanonthermalspectrum,withoutasignforacharac- Theexamplealsoindicatestherelativeenergetics: despite
teristicenergyscale(Fig.4). thefactthattheparticlenumberdensityofthegasexceeds
Thedifferentialenergyspectrumisapproximatelyapower thatoftheCRsbythreeordersofmagnitude,theinverseis
lfarowmintheenSerugny,fEor∝101E0−eV2.75<beEyo<ndfethwe1ra0n15geeVo.fTinhfleusepnecce- rporuogcehslsyctrauneifnodretehdelmeaedantopaarptpicrloexeimneartgeileys.eqTuhaelreefnoerregysudcehna-
tralfeaturesatseveral1015eVand1018eV,respectively,may sitiesofthetwocomponents.
indicatedifferentparticlesources,oralternatively,different
energydependencesofthepropagationconditionsinthesep-
arateenergyregions. ThecorrespondingestimateoftheCR
energydensityECRintheneighborhoodoftheSolarSys-
temisoftheorderof1eV/cm−3,aboutequaltothethermal
energydensityEgasoftheInterstellargasaswellasthetyp-
icalInterstellarmagneticenergyEmag,measuredbyother
GCR COMPOSITION, SPECTmReanUs:MEC,RO∼ERgaIsG∼IENmag.Ihavediscussedthesignifi-
canceofthisequalitybefore.
3 regions
-HighEnergy<PeV
-VeryHighEnergy(knee)PeV-EeV
-UltraHighEnergy(ankle)>EeV
keV=103eV MeV=106eV Fig.5. Totalenergydistributionofthermalplasma(gas)plusnon-
thermalplasma(CRs)nearadiffusivelyacceleratingshockwave:
GeV=109eV TeV=1012eV
thethermal(Maxwellian)energydistributionjoinsrathersmoothly
PeV=1015eV EeV=1018eV tothenonthermalpowerlawCRdistributionatan“injection”en-
ZeV=1021eV eOrnglyytshuaptrias-stheevremraalltpimaretsicllaersgaebrothveanthtihseinmjeecatniotnheernmearglyencearngypaErttihc-.
ipateinthecollectiveaccelerationprocess(adaptedfromMalkov
andVo¨lk,1998;courtesy“SterneundWeltraum”).
Tevatron collider
2 TeV cm 10 PeV lab
3.2 CosmicRaysourcespectra,composition
⇒
Large Hadron Collider TheobservedCRenergyspectraarenotnecessarilyidenti-
calwiththespectraoftheparticlesastheyareemittedfrom
14 TeV cm 400 PeV lab
⇒ theirsources.Theconnectionbetweenthetwoisrathergiven
bytheparticlepropagationproperties. Observationsshow
[Volk,ICRC,2001:3] thattheratiobetweentheenergyspectraofCRspallation
JOHNNORBURY (NASALANGLEY) SPACEtFRhieAgD.sIp4Ae.TcItTOruNhmeailsl-apaprotiwcleerClaRw,esWnleigErghDytNlyEsSpsDeteAceYtrpuJeUmnNi.nEgF1oa1tr,2aE0f1e4>∼w110019G5/ee7VV0,, p(Froigd.u6c)ts. aFnodrethneeirrgipersimabaoryvep1ar0tiGcleeVs/dneuccrleeaosnesthwisitthranensleartgeys
theso-calledKnee,andhardeningatafew1018eV,theso-called directlyintoacorrespondingenergydependenceoftheav-
Ankle.(AdaptedfromCroninetal.1997;courtesyS.Swordy.) erageamountofInterstellarmatter“seen”byCRparticles.
Ifweassumetheparticlestobeproduceddeeplyinsidethe
Howshouldwepicturetheoverallenergydistributionof denseGalacticgasdiskthenthisimpliesashorterresidence
thethermalgasplustheCRsastheycoexistinagivenvol- timethereforhigherenergyparticlesthanforthoseoflower
umeelementinspace? Thisquestionhasnouniqueanswer energybeforetheyeventuallyescapetoIntergalacticSpace.
because, evenifthegasandtheCRsareenergizedatthe Letusnowinadditiontaketheparticlesourcesaswellas
sameplaceinacosmicacceleratorlikeaSolarFlareoraSu- theparticlesreleasedfromthemtobeuniformlydistributed
pernovaRemnant,theirspatialpropagationcanbeverydif- acrosstheGalacticdiskthatincludesalsotheSolarSystem
Hadrons / Pions
GCR HIGH ENERGY < PEV
•  Maximum cosmic ray intensity
•  0.1 - 10 GeV
Space radiation problem
•  almost no data
GCR (primary) composition
•  1 - 10 GeV
98% nuclei, 2% e+e−
Nuc•l eaTrhceoomryp olenaesnt t :
87% Huynddroegrsetnood
12% He• liu 1m - 10 GeV
1% heavy nuclei
GCR origin
Emitted in stellar wind &
flares & accelerated by
supernova shock waves
[Simpson,Ann.Rev.Nucl.Part.Sci.33,323,1983]
(within our Galaxy)
JOHNNORBURY (NASALANGLEY) SPACERADIATION WEDNESDAYJUNE11,2014 10/70