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Update on the Worsening Particle
Radiation Environment
Observed by CRaTER
N A Schwadron, F Rahmanifard, J. Wilson, A P Jordan,
H E Spence, C J Joyce, J B Blake, A W Case, W d Wet,
W M Farrell, J C Kasper, M D Looper, N Lugaz, L Mays,
J E Mazur, J Niehof, N Petro, C W Smith, L W
Townsend, R Winslow and C Zeitlin
Radiation
Hazards,
Interactions • Galactic Cosmic
Rays (GCRs)
– Steady Background
– Career limit in ~ 1-3 years
• Solar Energetic Particles (SEPs)
– Acute Sources
– ESPs versus impulsive component
– Time-dependent response
ACE &
Ulysses
Comp.
Pro
ton
sp
ee
d
Norm
aliz
ed
density
Norm
aliz
ed
tem
p
Dynam
ic
pre
ssure
Reduced
Density
and
Dynamic
Pressure
McComas et al., 2008
Schwadron and McComas, 2008
Open Flux Depletion
Connick et al., Astrophys. J., 2011.
There is a 2-phase depletion of open field lines: first during
the “normal phase” of solar min when ICME activity is
small, and then later when ICME activity is virtually zero.
Rahmanifard et al., 2016
Integration into Heliospheric Models
|B| = 2/4R12 where
R1 = 1 AU;
ICME = 1 x 1013 Wb;
D = 1/2;
ic = 40 days;
0 = 2.5 years;
d = 4.4 years;
Flo = 0.5 day1;
fhi = 3 day1;
flr = 4 x 1014 Wb (|B| = 2
nT). More recent theoretical
coniderations are predicting
a lower flux floor.
Schwadron et al., Astrophys. J. Lett., 722, L132, 2010.
Continued Decay of Magnetic Flux in
the Dalton-like Minimum
Goelzer et al., ApJ, 2013
Strong Reduction in Field
Possible – Much Higher GCR Flux
Rahmanifard et al., 2016
SCHWADRON ET AL., SPACE WEATHER, 2014a
• Highest GCR doses
in space age in
recent cycle 23 solar
minima
• Continues trend
observed by
Ulysses, ACE
Schwadron et al., Space Weather, 2017
0 2 4 6 8 10 12 14 16 1950 1960
1970 1980
1990 2000
2010 0 200
400
600
800
1000
1200Lunar Surface Dose Rate (cGy/yr)
Sunspot Number
Year
ACECRaTER
Sunspot Number
Model
Solar Proton Model Prediction/Validation After Schwadron et al., 2012
SEP Events During 2012:
Indicators of Larger SEP Events
in the New Cycle (24)
• Shown here are the major SEP events of 2012
and the comparisons between CRaTER
observations (blue) and prediccs predictions (red
and green).
• Agreement reveals overall accuracy of models,
while deviations likely reveal heavy ion
contributions to dose observed by CRaTER
60 65 70 75 80DOY
100
101
102
103
104
105
Dose
Ra
te(u
Gy/h
r)
CRaTER (blue) EMMREM (red)
134 136 138 140 142 144 146DOY
100
101
102
103
104
105
Dose
Ra
te(u
Gy/
hr)
CRaTER (blue) EMMREM (red)
Ja
n.
23
rd ,
2012 E
vent
Mar
7, 2012 E
vent
May 1
6,
20
12 E
vent
MeWaldt et al., 2015 Schwadron et al., 2017
SCHWADRON ET AL., SPACE WEATHER, 2014a
Joyce et al., 2015
Schwadron et al., 2017
Schwadron et al., 2017
10-2
10-1
100
101
102
Lu
na
r D
ose
Ra
te (
cG
y/d
ay
)
CRaTER D1D2
CRaTER D3D4
CRaTER D5D6
CRaTER Microdosim eter
10-3
10-2
10-1
100
101
102
Lu
na
r D
ose
Ra
te (
cG
y/d
ay
)
PREDICCS Al 0.3, H2O 10 g/cm 2
PREDICCS Al 1, H2O 10 g/cm 2
PREDICCS Al 5, H2O 10 g/cm 2
PREDICCS Al 10, H2O 10 g/cm 2
17/09
/04
17/09
/06
17/09
/08
17/09
/10
17/09
/12
17/09
/14
17/09
/16
17/09
/18
17/09
/20
10-4
10-2
100
102
104
pro
ton
/cm
2-s
-sr-
Me
V
PREDICCS Al 0.3, H2O 1 g/cm 2
PREDICCS Al 1, H2O 1 g/cm 2
PREDICCS Al 5, H2O 1 g/cm 2
PREDICCS Al 10, H2O 1 g/cm 2
2.5 MeV
6.5 MeV
11.6 MeV 30.6 MeV 63.1 MeV 165.0 MeV 433.0 MeV
X9 Flare
Sep 10X8 Flare
Sep 6
X9.3 Flare
Sep 6
X8.2 Flare
Sep 10• Example of a
large event
during
decline of
cycle 24
• Note
importance of
seed
population
Schwadron et al., 2017
• First event
had clear
shock, and
ESP
• Second event
shows
prompt
acceleration
Schwadron et al., 2017
Conclusions
• Radiation levels continue to increase due to
weakening solar activity
• Dose rates even higher than predicted in
2014
• Large events (Sep 2017) in decline of cycle
24 indicate that weak activity does not
exclude large SEP events
• Overall, SEP event probabilities still quite
low during cycle 24