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Space Weather Radiation HazardsREU Summer School
ByRon Zwickl
NOAASpace Environment Center
June 14, 2007
June 14, 2007 REU Summer School
• Simple Tutorial– Cosmic Rays– Solar Radiation Storms– Earth’s Influence
• Magnetospheric Shielding
• Atmospheric Shielding
• Radiation Impacts on Airline Passengers
• Radiation Dangers to Astronauts
Space Weather Radiation Hazards
Outline
June 14, 2007 REU Summer School
Space Radiation
• Composed of two major components– Cosmic Rays
• Always present and very energetic
• Composed of many different elements
June 14, 2007 REU Summer School
Cosmic Rays
• Composed of many different Elements, such as Hydrogen Helium, Carbon, and Iron
• They cover a very wide range of energies
•They are always present
June 14, 2007 REU Summer School
Space Radiation
• Composed of two major components– Cosmic Rays
• Always present and very energetic
• Composed of many different elements
• Intensity varies throughout 11 year Solar Cycle
June 14, 2007 REU Summer School
Space Radiation
• Composed of two major components– Cosmic Rays
• Always present and very energetic
• Composed of many different elements
• Intensity varies throughout 11 year Solar Cycle
• Intensity varies with Solar Activity
June 14, 2007 REU Summer School
Space Radiation
• Composed of two major components– Cosmic Rays
• Always present and very energetic
• Composed of many different elements
• Intensity varies throughout 11 year Solar Cycle
• Intensity varies with Solar Activity
– Solar Radiation Storms• Infrequent, very intense, with rapid onsets
June 14, 2007 REU Summer School
Solar Radiation StormS3
S2
S4
S1
Flight crews Interested in this curve
June 14, 2007 REU Summer School
Space Radiation
• Composed of two major components– Cosmic Rays
• Always present and very energetic
• Composed of many different elements
• Intensity varies throughout 11 year Solar Cycle
• Intensity varies with Solar Activity
– Solar Radiation Storms• Infrequent, very intense, with rapid onsets
• Composed of many different elements
• Origin strongly linked to Solar Activity
• Variable energy and composition dependence
June 14, 2007 REU Summer School
Space Radiation
• Earth’s Influence on the radiation level– Magnetic Field Shielding
• Always present, but has holes!
June 14, 2007 REU Summer School
Earth’s
Magnetic Shieldto Cosmic Ray Access
Magnetic Poles: Open
Magnetic Equator: >15 GeV
Red bar varies as functionof magnetic latitude
June 14, 2007 REU Summer School
Space Radiation
• Earth’s Influence on the radiation level– Magnetic Field Shielding
• Always present, but has holes!
– Geomagnetic Activity• Changes magnetic field shield location
Influence of Geomagnetic Activity on auroral boundary(geomagnetic poles expand with increased activity)
June 14, 2007 REU Summer School
Space Radiation
• Earth’s Influence on the radiation level– Magnetic Field Shielding
• Always present, but has holes!
– Geomagnetic Activity• Changes magnetic field shield location
– Atmospheric Shielding• Upper atmosphere acts as a target
• Lower atmosphere acts as absorbing shield
Photon cascade in lead plates in cloudchamber.
Maximum numberof particles afterpassing through10 cm of lead
Incident photon is several GeV
June 14, 2007 REU Summer School
Space RadiationSummary
• Two primary components• Cosmic Rays
• Steady with some variability• Solar Radiation Storms
• Rare, highly variable, and can be intense
• Earth’s natural defenses• Magnetic field shields Earth
• Makes calculations very complex• Geomagnetic Latitude dependent• Geomagnetic activity can expand poles
• Atmosphere acts as target and as shield• Radiation strongly dependent upon altitude
June 14, 2007 REU Summer School
Space Weather and Aviation Space Weather and Aviation
June 14, 2007 REU Summer School
Issue Time: 2001 Nov 04 2045 UTCALERT: Solar Radiation Alert at Aviation Flight AltitudesConditions Began: 2001 Nov 04 2035 UTC
Altitude Solar proton effective dose rate (feet) (millisieverts/hour) * --------------------------------------------------------------- 20 000 <0.0010 30 000 0.0052 40 000 0.019 50 000 0.040 60 000 0.060 70 000 0.074 80 000 0.088 ---------------------------------------------------------------- * Estimates at high latitude locations. Dose rates are based on near real-time GOES satellite readings and are recalculated every 3 minutes.
Slide 7
Kyle Copeland & Wallace Friedberg Civil Aerospace Medical Institute, AAM-610
June 14, 2007 REU Summer School
Effective Doses From Solar Radiation at 40 000 ft for Selected Solar Proton Events From January 1986 Through December 2001 (16 y)
Total Effective Dose (mSv) -----------------------------Date Event Time (hh:mm)* 3 h 5 h 10 h----------------------------------------------------------------------------------Aug. 16, 1989 GLE 41 01:10 0.055 0.072 0.087Sept. 29, 1989** GLE 42 08:35 0.26 0.42
0.59Oct. 19, 1989 GLE 43 20:30 0.074 0.17 0.41Oct. 22, 1989 GLE 44 03:25 0.15 0.19 0.23Oct. 24, 1989 GLE 45 10:25 0.14 0.37 0.64May 24, 1990 GLE 48 00:05 0.13 0.019 0.026Jun. 15, 1991 GLE 52 00:50 0.041 0.048 0.055Nov. 2, 1992 GLE 54 00:20 0.039 0.054 0.072Nov. 6, 1997** GLE 55 08:00 0.15 0.26 0.39Jul. 14, 2000** GLE 59 07:05 1.1 1.3 1.51Apr. 15, 2001** GLE 60 07:35 0.73 0.97 1.1Apr. 18, 2001** GLE 61 01:15 0.049 0.083 0.14Nov. 4, 2001** GLE 62 03:20 0.082 0.12 0.17Dec. 26, 2001 GLE 63 01:35 0.069 0.081 0.090---------------------------------------------------------------------------------- * Time that recommended maximum flight altitude is below 40 000 ft** Dose rates are underestimated for more than 0.5 h
Slide 9
Kyle Copeland & Wallace Friedberg Civil Aerospace Medical Institute, AAM-610
Radiation Risks to Astronauts
Michael J. Golightly
NASA routinely avoids the radiation belts in their scheduling of space walks.
June 14, 2007 REU Summer School
DEEP SPACE GCR DOSES
• Annual bone marrow GCR doses will range up to ~ 15 cGy at solar minimum (~ 40 cSv) behind ~ 2cm Al shielding
• Effective dose at solar minimum is ~ 45-50 cSv per annum
• At solar maximum these are ~ 15-18 cSv• Secondary neutrons and charged particles
are the major sources of radiation exposure in an interplanetary spacecraft
• No dose limits yet for these missions
June 14, 2007 REU Summer School
GCR Risks• Clearly, annual doses < 20cGy present no acute
health hazard to crews on deep space missions• Hence only stochastic effects such as cancer
induction and mortality or late deterministic effects, such as cataracts or damage to the central nervous system are of concern.
• Unfortunately, there are no data for human exposures from these radiations that can be used to estimate risks to crews
• In fact, it is not clear that the usual methods of estimating risk by calculating dose equivalent are even appropriate for these particles
June 14, 2007 REU Summer School
SOLAR PARTICLE EVENT DOSES
• Doses can be large in deep space but shielding is possible
• August 1972 was largest dose event of space era (occurred between two Apollo missions)
June 14, 2007 REU Summer School
R a d ia tio n D an g e rs to A s tro n a u ts
B etw e en A p o llo 1 6 an d 1 7 ,o n e o f th e la rg es t so la r p ro to nev e n ts ev e r re co rd e d a rr iv eda t E a rth . T h e rad ia tio n le v e lsan a s tro n au t in s id e a sa te llitew o u ld e x p e rie n ce d u r in g th isev e n t w ere s im u la ted . E v e nin s id e a sp a ce c ra ft, a s tro n a u tsw o u ld h a v e ab so rb ed le th a ld o ses o f rad ia tio n w ith in 1 0 h rsa f te r th e s ta rt o f th e e v en t(4 0 0 0 m S v ).
June 14, 2007 REU Summer School
POSSIBLE ACUTE EFFECTSAugust 1972 SPE
• Bone marrow doses ~ 1 Gy delivered in a day may produce hematological responses and vomiting (not good in a space suit)
• Skin doses ~15-20 Gy could result in skin erythema and moist desquamation (in some cases)- doses inside nominal spacecraft might
limit effects to mild erythema
June 14, 2007 REU Summer School
SOLAR PARTICLE EVENT DOSES
• Ice core data from the Antarctic indicate that the largest event in past ~ 500 years was probably the Carrington Flare of 1859- fluence ~ 20 larger than Aug 72- actual spectrum energy dependence unavailable, assume both hard and softspectra
June 14, 2007 REU Summer School
CARRINGTON FLARE DOSES(9/89 Spectrum)
• Bone marrow doses ~ 1-3 Gy possible inside a spacecraft (life threatening)
• “Storm” shelter of about 18 cm Al needed to shield to the applicable deterministic limits (30 d limits of 0.25 Gy-Eq)
• Major problem for non radiation hardened electronics built with COTS components- up to 50 krads or more of total ionizing dose
June 14, 2007 REU Summer School
Mars Surface(mainly protons and neutrons)
GCR Solar Minimum
GCR Solar Maximum
October 1989 SPE
Dskin 5.7 cGy/yr 2.7 cGy/yr 3.2 cGy
Hskin 13.2 cSv/yr 6.7 cSv/yr 4.8 cSv
DBFO 5.5 cGy/yr 2.6 cGy/yr 1.7 cGy
HBFO 11.9 cSv/yr 6.1 cSv/yr 2.7 cSv
June 14, 2007 REU Summer School
CONCLUDING REMARKS
• GCR exposures will be a problem for Mars missions due to large effective doses
• Organ doses received from large SPEs can be hazardous to crews of vehicles in deep space
- exposures that are survivable with proper medical treatment on Earth may not be survivable in space
June 14, 2007 REU Summer School
CONCLUDING REMARKS (cont.)
• Aside from acute effects, a single large SPE can expose a crewmember to an effective dose that exceeds their career limit
• Due to their relatively soft energy spectra, most SPE doses can be substantially reduced with adequate shielding (several cm Al or equivalent)
• A worst case event similar to the assumed Carrington Flare of 1859 could be catastrophic in deep space depending on spectral hardness
June 14, 2007 REU Summer School
CONCLUDING REMARKS (cont.)
• Results presented only for aluminum• Other materials with low atomic mass
numbers are better LH2 reduces GCR dose equivalent by ~ one-half
• In situ materials on lunar or Martian surface can be used to provide shielding (similar to Al in shielding characteristics)
• Martian atmosphere is a relatively thick shield for operations on Mars surface
~ 16-20 g cm-2 CO2
June 14, 2007 REU Summer School
October 1989 SPE
0.1
1
10
100
1000
10000
0 50 100 150 200 250 300
Time (h)
Pro
ton
s-cm
-2-s
-1-s
r-1
>30 Mev>50 MeV>60 MeV>100 MeV
June 14, 2007 REU Summer School
AUGUST 1972 SKIN DOSE RATE
0
20
40
60
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120
140
0 5 10 15 20 25 30
Time (hours)
Ski
n D
ose
Rat
e (c
Gy/
hr)
1 g/cm2 Al
2 g/cm2 Al
5 g/cm2 Al