Space Weather Radiation Hazards REU Summer School By Ron Zwickl NOAA Space Environment Center June...

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


Space Radiation

• Composed of two major components– Cosmic Rays

• Always present and very energetic

• Composed of many different elements

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


GALACTIC COSMIC RAYS


Space Radiation




• Intensity varies throughout 11 year Solar Cycle

June 14, 2007 REU Summer SchoolRadiation level varies throughout the solar cycle


Space Radiation





• Intensity varies with Solar Activity


Space Radiation






– Solar Radiation Storms• Infrequent, very intense, with rapid onsets


Solar Radiation StormS3

S2

S4

S1

Flight crews Interested in this curve

Polar Satellite Image Degradation during July 14, 2000 Solar Radiation Storm


Space Radiation






– Solar Radiation Storms• Infrequent, very intense, with rapid onsets


• Origin strongly linked to Solar Activity

• Variable energy and composition dependence


Space Radiation

• Earth’s Influence on the radiation level– Magnetic Field Shielding

• Always present, but has holes!


Open

Open

Closed

Cosmic Ray Access


Earth’s

Magnetic Shieldto Cosmic Ray Access

Magnetic Poles: Open

Magnetic Equator: >15 GeV

Red bar varies as functionof magnetic latitude


Space Radiation



– Geomagnetic Activity• Changes magnetic field shield location

Influence of Geomagnetic Activity on auroral boundary(geomagnetic poles expand with increased activity)


Space Radiation



– 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


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


Space Weather and Aviation Space Weather and Aviation

http://affiliates.art.com/get.art?T=15033627&A=204670&L=8&P=10119858&S=4&Y=6584

Lt Col Thomas C. Hankins USAF


FRA to DFW flight


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


Space Weather and Aviation Space Weather and Aviation


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.


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


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


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)


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 ).


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


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


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


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


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


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


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

parting shot …

Kanzelhoehe Solar Observatory, Austria

December 1, 2000


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


AUGUST 1972 SKIN DOSE RATE

0

20

40

60

80

100

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


TOKYOOSAKA

HONG KONGSHANGHAI

CHICAGO

NEW YORK

82 N

#1

#1A

#2

#3

#4

UAL POLAR ROUTES

BEIJING

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Space Weather Radiation Hazards REU Summer School By Ron Zwickl NOAA Space Environment Center June...

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