Interaction of Interaction of solar and galactic cosmic rays solar and galactic cosmic rays

with Earth’s atmospherewith Earth’s atmosphere

Contributors:Contributors: Rolf Bütikofer 1, Laurent Desorgher 1, Erwin Flückiger 1, Gennady Kovaltsov 5,Marisa Storini 2, Ilya Usoskin 3, Peter Velinov 4

1 University of Bern, Switzerland2 IFSI-Roma/INAF, Roma, Italy3 Sodankylä Geophysical Observatory, University of Oulu, Finland4 Solar-Terrestrial Influences Laboratory, Bulgarian Academy of Sciences, Sofia, Bulgaria5 Ioffe Physical-Technical Institute, St.Petersburg, Russia

CRII models: basic information Bern model (ATMOCOSMIC)Bern model (ATMOCOSMIC)Desorgher et al., Internat. J. Modern Phys. A, 20, 6802-6804 (2005).

Responsible person:

Laurent DesorgherPhysikalisches Institut, University of Bern, Switzerland

Also: Erwin FlückigerFan Lei, QinetiQ, ESA/ESTEC

Program basis: GEANT 4 application

Physics behind: Monte-carlo of the cascade, all included

CR particles: protons + -particles.

Energy range: 10 MeV ->

Validity: below 100 g/cm2 (15 km) -10% at 10 g/cm2 (30 km) – a factor of 2

Oulu CRII modelOulu CRII modelUsoskin and Kovaltsov, J. Geophys. Res., 111, D21206 (2006).

Responsible person:

Ilya UsoskinSodankylä Geophysical Observatory University of Oulu, Finland

Also: Gennady Kovaltsov Ioffe Phys-Tech. Institute, St. Petersburg, Russia

Program basis: CORSIKA + FLUKA

Physics behind: Monte-Carlo of the cascade, all included

CR particles: protons and -particles explicitly

Energy range: 10 MeV - 5000 GeV/nuc

Validity: below 100 g/cm2 (15 km) -10% at 10 g/cm2 (30 km) – a factor of 2

Sofia upper atmosphere modelSofia upper atmosphere modelVelinov, and Mateev: C. r. Acad. bulg. Sci., 58, 5, 511-516 (2005).

Responsible person:

Lachezar Mateev,Marussia BucharovaPeter VelinovBulgarian Academy of Sciences, Sofia, Bulgaria

Program basis: Analytical model, spherical atmosphere

Physics behind: Direct ionization (Thin target), no cascade

CR particles: protons, , L, M, H, VH

Energy range: 1 MeV – 100 GeV

Validity: > 16 km (<100 g/cm2) - minimum> 12 km (<180 g/cm2) - maximum

Modelling

Direct ionization by primaries: Thin target model (analytics)

Cascade: Monte-Carlo

Cosmic Ray Induced Ionization

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 m

2 s

r se

c]-1

T [GeV/nuc]

protons

A

Y [s

r 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.

Comparison with observations

1

10

100

1000

10 100 1000

h (g/cm2)

Ion.

rat

e (c

m3 s

ec a

tm)-1

Neher, 1971

Rosen et al., 1985

Lowder, 1972

Bern model

Oulu model

Models agree with the observations and with each other within 10% below 15 km (>100 g/cm2). They start underestimating the ionization at higher altitudes and the underestimate becomes a factor of 2 in the upper few g/cm2 (> 40 km).

Upper atmosphere

Electron production rate q from different species of CR for the solar minimum conditions (Sofia model).

Momentary effect of a severe SEP event

CRII in the upper troposphere (300 g/cm2) at 06:55 UT of 20-Jan-2005 (ATMOCOSMIC results)

Net effect of a severe SEP event

Daily averaged CRII (normalized to the GCR) in a polar region (Oulu results).

The net effect is negativenegative (suppressed ionization) below 100 g/cm2.

12 14 16 18 20 22 24 26

1000

800

600

400

200

0

Day of Jan-2005

Atm

. d

ep

th (

g/c

m2)

0.6000

1.067

1.897

3.374

6.000

relative CRII, polar region

Atmospheric chemistry and SEP events

Ozone variability (MLS/AURA data) for several atmospheric levels (after Damiani et al., 2007a).

Conclusion

An overview is given of the study of cosmic ray terrestrial effects, in the frameworks of COST-724 action.

• Three models of CRII have been developed:– Bern model is most suitable for precise simulations of CRII in the

troposphere-lower stratosphere;– Oulu model is optimized for the study of long-term CRII

variability;– Sofia model is specialized in modelling of thin and intermediate

target conditions (upper atmosphere and planets with thin atmospheres)

• An effect of SEP events has been studied in great detail, that is significant in the polar region and in the upper atmosphere.

Acknowledgements

We are greatful to the COST-724 action for giving us a possibility to work together on this problem.

Particularly useful was a STSM (hosts – Desorgher and Flückiger, guests – Usoskin and Velinov) to the University of Bern in Nov. 2005.