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Transcript of 1 Cosmic rays and climate Ilya G. Usoskin Sodankylä Geophysical Observatory, University of Oulu,...
1
Cosmic rays
and climate Ilya G. Usoskin
Sodankylä Geophysical Observatory, University of Oulu, Finland
2
Cosmic Ray Induced Ionization (CRII)
CRII is an important factor of the outer space influences on atmospheric properties.
CR undergo nuclear interactions with
the air
Nucleonic, electromagnetic, muon
cascade
ionization of the ambiente air
3
Modelling
Direct ionization by primaries: • Analytics – “Thin” and “thick” target model. • Significant contribution from other sources.
Cascade: Monte-Carlo
4
CRII models: basic information
Monte-CarloMonte-Carlo: :
Oulu CRAC:CRII (CORSIKA+FLUKA)Oulu CRAC:CRII (CORSIKA+FLUKA) Bern model ATMOCOSMIC (GEANT-4):Bern model ATMOCOSMIC (GEANT-4):
Usoskin et al., J. Atm. Solar-Terr. Phys, (2004). Desorgher et al., Int. J. Mod. Phys. A, (2005) Usoskin, Kovaltsov, J. Geophys. Res., (2006, 2010). Scherer et al. Space Sci. Rev. (2006).
Physics behind: Monte-Carlo simulation of the cascade, all species and processes included
Accuracy: - below 100 g/cm2 (15 km) -10%
Output of the modelsOutput of the models
Cosmic ray induced ionization (CRII) rate, i.e. the number of ion pairs produced in 1 cm3 (g) per second.
Equilibrium concentration depends on the recombination processes and ion mobility and forms an independent task.
5
CRII: details
The results of Monte-Carlo simulations of the atmospheric cascade for primary protons with energy 0.2 GeV, 10 GeV and 100 GeV.
0 200 400 600 800 1000100
101
102
103
104
105
106
0 200 400 600 800 1000103
104
105
106
0 200 400 600 800 1000104
105
106
107
Y [s
r cm
2 g-1]
Atm. depth [g cm-2]
A) p, 200 MeV
SUM EM MUON HADR
B) p, 10 GeV
Atm. depth [g cm-2]
C) p, 100 GeV
Atm. depth [g cm-2]
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CRII: ionization function
0.1 1 10 100 1000100
101
102
103
104
105
0.1 1 10 10010
-2
10-1
100
101
102
103
104
0.1 1 10 100 1000100
101
102
103
104
105
106
107
F [G
eV
se
c g
]-1
T [GeV/nuc]
100 300 500 700 1030
C B
-particles
J [G
eV
/nu
c m2
sr
sec]
-1
T [GeV/nuc]
protons
A
Y [sr
cm
2 g
-1]
T [Gev/nuc]
100 300 500 700 1030 , 500
CT iii dTTxYTJQxQ ),(),(),(
CRII is defined as an integral product of the ionization yield function Y and the energy spectrum of GCR J.
The most effective energy of CRII depends on the atmospheric depth – from ≈1 GeV/nuc in the stratosphere to about 10 GeV/nuc at the sea-level.
7
CRII: altitude vs. latitude
252015
10
54
3
2
1
0 2 4 6 8 10 12 14
1000
800
600
400
200
CR
II (c
m-3 s
ec-1
)
Geom. cutoff (GV)
Atm
. dep
th (
g/cm
2)
0
10
20
30
40
Alti
tude
(km
)
8
Comparison with measurements
100 1000
10
100
Q [c
m-3 s
ec-1 a
tm-1]
P [hPa]
Measurements (Readings, Aug 2005)
Model (P
C=2.5 GV =650 MV)
9
Spatial distribution of CRII (cm-3 sec-1)
-180 -120 -60 0 60 120 180-90
-60
-30
0
30
60
90
10
17
24
31
38
45
CRII, 200 g/cm2
-180 -120 -60 0 60 120 180-90
-60
-30
0
30
60
90
10
17
24
31
38
45
CRII, 200 g/cm2
-180 -120 -60 0 60 120 180-90
-60
-30
0
30
60
90
1.5
1.6
1.7
1.9
2.0
2.1
CRII, 1025 g/cm2
Ground level 12 km altitude
Sol
ar m
axim
umS
olar
min
imum
-180 -120 -60 0 60 120 180-90
-60
-30
0
30
60
90
1.5
1.6
1.7
1.9
2.0
2.1
CRII, 1025 g/cm2
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CRII: last decades
CRII since 1951 at the atmospheric depth x=700 g/cm2 (about 3 km altitude) for polar regions and to the equator.
1950 1960 1970 1980 1990 2000 201070
75
80
85
90
95
100
105
Rela
tive C
RII
Pole Equator
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Long-term CRII
1700 1750 1800 1850 1900 1950 20004000
5000
6000
7000
QP
ole [g
-1se
c-1]
Years
Computed CRII at x=700 g/cm2 (about 3 km altitude) in a sub-polar region, based on cosmic ray flux reconstruction [Usoskin et al., 2002]. This is consistent with a ~0.15 %yr-1 decerase of the air conductivity (measured in Europe) between 1910’s and 1950’s [Harrison & Bennett, 2007]
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CR time profile for January 2005
Time profile of Oulu NM hourly count rate for January 2005 (http://cosmicrays.oulu.fi).
5 10 15 20 25 3080%
85%
90%
95%
100%
105%
200%
220%
240%
O
ulu
NM
co
un
t ra
te
Day of January 2005
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Ionization effect of GLE 20-01-2005
0.1 1 10 10010-1
100
101
102
103
104
105
106
107
108
102 103 104 105 106 107 108 1091000
100
10
CR
dai
ly fl
uenc
e (c
m2 s
r G
eV)-1
E (GeV)
Dep
th (
g/cm
2 )
CRII (g sec)-1
(A) Differential fluence of solar protons from the 20-01-2005 event and the daily fluence of GCR protons for the day of 20-01-2005, including the effect of the Forbush decrease (dotted line). The dashed curve depicts the average GCR proton fluence for January 2005.
(B) The vertical profile of the daily averaged CRII in the polar region from GCR (dotted curve) and SEP (solid curve) separately, for the day of 20 January 2005.
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Ionization effect of GLE
0 5 10 15
1000
500
0
Pc (GV)
h (g
/cm
2)
0.760
0.873
1.01
1.15
1.32
1.52
1.74
2.00
The relative ionization effect of GLE 20-Jan-2005 as function of the geomagnetic cutoff rigidity Pc and atmospheric depth h.
I
IIPchC GCRSEP
),(
15
How often do SEP events occur?
The probability of a SEP event to occur (McCracken et al., JGR, 2001)
16
Climate forcing
Climate
Internal forcing(volcanos, oceans)
Orbitalforcing
Direct solarforcing
IndirectSolar forcing ?
Anthropogenic!!!Anthropogenic!!!
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SA/CR climate
-4000 -3000 -2000 -1000 0 1000 20000
20
40
60
S
unsp
ot n
umbe
r
Years -BC/AD
Sunspot number reconstruction (Usoskin et al., 2007) along with the climate shifts in Europe to cold/wet conditions (Versteegh, 2005) for the last 6500 years:14 cold spells – vs – 15 Grand minima 12 coincide.
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Earth’s radiative equilibrium
absorbed solar radiation = emitted infrared radiation:
Black-body temperature255 K
Real temperature 288 K
19
CR vs. climate
Clouds play an important role in the radiation budget of the atmosphere by both trapping outgoing long wave radiation and reflecting incoming solar radiation. This This affects the amount of absorbed radiation, even without invoking notable changes in affects the amount of absorbed radiation, even without invoking notable changes in the solar irradiance.the solar irradiance.
Two possible mechanisms have been proposed:
• Ions + molecules complex cluster ions (aerosols)
grow by ion-ion recombination or ion-aerosol attachment
cloud condensation nuclei (Svensmark & Co; Yu 2002)
The atmosphere is not a Wilson chamber!
• GCR + SASA global electrical circuit ( vertical currents)
Ice in super-cooled water enhanced precipitation (Tinsley & Co.)
Hard to distinguish from other SA-driven effects.
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CLOUD+SKY experiment
Duplissi et al. (2010), Pedersen et al. (2011)A 10-fold increase of ionization (typical changes 25%) 3-fold formation rate, BUT…A 10-fold increase in SO2 (typical) 1000-fold formation rate change.Temperature, humidity also affect…
21
Marsh and Svensmark, JGR, 2003
Solar cycle
This result has been disputed.
22
Inter-annual scale
CR – cloud relation is not homogenous but depicts a
clear geographical pattern (Marsh & Svensmark, 2003;
Palle et al., 2004; Usoskin et al., 2004; Voiculescu et al.,
2006), including three major regions:
• NE Atlantics + Mediterranean (Europe);
• S Atlantic + W Indian;
• NW Pacific;
and almost no relation in other parts of the world.
-180 -120 -60 0 60 120 180-90
-60
-30
0
30
60
90 I(S)L
Correlation significance map – Palle et al. (2004)
Correlation map – Usoskin et al. (2004), Voiculecu et al. (2006)
23
Atmospheric responses to daily CR variations
Pudovkin & Veretenenko, JASTP, 1995:Change of the mean cloud cover (ground-based observations) after FD at high latitudes (> 60o N)
Roldugin & Tinsley, JASTP, 2004: changes in atmospheric transparency associated with FD at high latitudes (> 55o N)
Kniveton, JASTP, 2004: Todd & Kniveton, 2004;Zonal mean total cloud anomalies associated with FD – polar and equatorial regions.
Stozhkov et al. (Geom.Aer., 1996; J.Phys.D, 2003):Precipitation changes related to FD/SPE.
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BUT...
Calogovic et al. (2010) and Kristjansson et al. (2008) :
No notable effect of Forbush decreases in the cloud cover globally or in some regions.
(Kristjansson et al. if the effect exist, then only in South Atlantic)
Statistical results are inconclusive.
25
Direct evidence: 20-01-2005
• Mironova et al. (GRL, 2008) Decrease of the Aerosol index at Antarctic stations on 2-nd day after the event – columnar density.
• Mironova et al. (ACPD, 2011) Formation of CCN-size aerosols in the same region – altitude range 15-20 km.
Severe SEP event barely noticable effect. Serious limitation on the direct CR effect.
-6 -4 -2 0 2 4 6-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5AI
5 10 15 20 25 3010
15
20
25
Hei
ght (
km)
DOY 2005
0
0.5
1.0
1.5
2.0
2.5
26
Conclusions
Cosmic rays form the main source of atmospheric ionization and related physical-chemical changes in the low-mid atmosphere. This is well understood and modelled.
The direct effect of CR on clouds is unclear, most likely it is
small (experiments + a case study of a severe SPE).
Indirect effect (top-down dynamic strato-troposphere coupling) – hard to distinguish from SI effects.
CR may play a role on the long-term scale, but difficult to distinguish from solar irradiance variations.
It is not CR per se but its variability, that may affect climate.
27
FAQ
Do CR affect climate probably YESYES, but we don’t know how...
Would we see clouds if there were no cosmic rays? YESYES
Would climate be somewhat different if there were no CR? Probably YESYES
Are we sure in a strong solar/CR-climate relation? NONO, but a bulk of indirect evidences + no solid contra-proof
Do we know exact mechanism of such a relation?
NONO, but some qualitative ideas and indirect experiments
Is the present GW a result of the solar activity? partly YESYES (before 1950-1970) and probably NONO (since 1970)
28