Space Weather
Radiation Hazards
REU Summer School
By
Ron Zwickl
NOAA
Space Environment Center
June 14, 2007
Space Weather
Radiation Hazards
Outline
• Simple Tutorial
– Cosmic Rays
– Solar Radiation Storms
– Earth’s Influence
• Magnetospheric Shielding
• Atmospheric Shielding
• Radiation Impacts on Airline Passengers
• Radiation Dangers to Astronauts
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
are “born” throughout
the known Universe
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
GALACTIC COSMIC RAYS
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
Radiation level varies
throughout the solar cycle
REU Summer School
June 14, 2007
Space Radiation
• Composed of two major components
– Cosmic Rays
•
•
•
•
June 14, 2007
Always present and very energetic
Composed of many different elements
Intensity varies throughout 11 year Solar Cycle
Intensity varies with Solar Activity
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
S4
Solar Radiation Storm
S3
S2
S1
Flight crews
Interested in this curve
June 14, 2007
REU Summer School
Polar Satellite Image Degradation during July 14, 2000 Solar Radiation Storm
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
•
•
•
June 14, 2007•
Infrequent, very intense, with rapid onsets
Composed of many different elements
Origin strongly linked to Solar Activity
Variable energyREU
andSummer
composition
dependence
School
Space Radiation
• Earth’s Influence on the radiation level
– Magnetic Field Shielding
• Always present, but has holes!
June 14, 2007
REU Summer School
Cosmic Ray Access
Open
Closed
Open
June 14, 2007
REU Summer School
Earth’s
Magnetic Shield
to Cosmic Ray Access
Magnetic Poles: Open
Magnetic Equator: >15 GeV
Red bar varies as function
of 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
June 14, 2007
REU Summer School
Influence of Geomagnetic Activity on auroral boundary
(geomagnetic poles expand with increased activity)
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
June 14, 2007
REU Summer School
Photon cascade in
lead plates in cloud
chamber.
Maximum number
of particles after
passing through
10 cm of lead
Incident photon is
several GeV
Space Radiation
Summary
• 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
June 14, 2007
REU Summer School
Lt Col Thomas C. Hankins USAF
FRA to DFW flight
June 14, 2007
REU Summer School
Issue Time: 2001 Nov 04 2045 UTC
ALERT: Solar Radiation Alert at Aviation Flight
Altitudes
Conditions Began: 2001 Nov 04 2035 UTC
Slide 7
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.
June 14, 2007
REU Summer School
Kyle Copeland & Wallace Friedberg
Civil Aerospace Medical Institute, AAM-610
Space Weather and Aviation
June 14, 2007
REU Summer School
Slide 9
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)*
3h
5h
10 h
---------------------------------------------------------------------------------Aug. 16, 1989
GLE 41
01:10
0.055
0.072
0.087
Sept. 29, 1989**
GLE 42
08:35
0.26
0.42
0.59
Oct. 19, 1989
GLE 43
20:30
0.074
0.17
0.41
Oct. 22, 1989
GLE 44
03:25
0.15
0.19
0.23
Oct. 24, 1989
GLE 45
10:25
0.14
0.37
0.64
May 24, 1990
GLE 48
00:05
0.13
0.019
0.026
Jun. 15, 1991
GLE 52
00:50
0.041
0.048
0.055
Nov. 2, 1992
GLE 54
00:20
0.039
0.054
0.072
Nov. 6, 1997**
GLE 55
08:00
0.15
0.26
0.39
Jul. 14, 2000**
GLE 59
07:05
1.1
1.3
1.51
Apr. 15, 2001**
GLE 60
07:35
0.73
0.97
1.1
Apr. 18, 2001**
GLE 61
01:15
0.049
0.083
0.14
Nov. 4, 2001**
GLE 62
03:20
0.082
0.12
0.17
Dec. 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
June 14, 2007
REU Summer School
Kyle Copeland & Wallace Friedberg Civil Aerospace Medical Institute, AAM-610
Radiation Risks to Astronauts
NASA routinely
avoids the
radiation belts in
their scheduling
of space walks.
Michael J. Golightly
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
Radiation Dangers to Astronauts
Between Apollo 16 and 17,
one of the largest solar proton
events ever recorded arrived
at Earth. The radiation levels
an astronaut inside a satellite
would experience during this
event were simulated. Even
inside a spacecraft, astronauts
would have absorbed lethal
doses of radiation within 10 hrs
after the start of the event
(4000 mSv).
June 14, 2007
REU Summer School
POSSIBLE ACUTE EFFECTS
August 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
5.7 cGy/yr
GCR Solar
Maximum
2.7 cGy/yr
October
1989 SPE
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
Dskin
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
hardness
Junespectral
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
-2 CO
~
16-20
g
cm
June 14, 2007
REU Summer
School
2
parting shot …
Kanzelhoehe Solar Observatory, Austria
December 1, 2000
October 1989 SPE
10000
Protons-cm-2-s-1-sr-1
1000
>30 Mev
>50 MeV
>60 MeV
>100 MeV
100
10
1
0.1
0
June 14, 2007
50
100
150
Time (h)
200
REU Summer School
250
300
AUGUST 1972 SKIN DOSE RATE
140
Skin Dose Rate (cGy/hr)
120
100
1 g/cm2 Al
80
2 g/cm2 Al
60
5 g/cm2 Al
40
20
0
0
5
10
15
20
Time (hours)
June 14, 2007
REU Summer School
25
30
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