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]

6

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

10

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

11

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]

12

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

13

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.

14

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!!!

17

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.

18

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.

20

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.

24

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