Cosmic Rays in the earth s atmosphere. Ilya Usoskin Sodankylä Geophysical Observatory ReSoLVE Center of Excellence, University of Oulu, Finland

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1 1 Cosmic Rays in the earth s atmosphere Ilya Usoskin Sodankylä Geophysical Observatory ReSoLVE Center of Excellence, University of Oulu, Finland

2 Outline 2 Atmosphere Cosmic-ray induced atmospheric cascade Ground-based measurements of cosmic rays Atmospheric effects of cosmic rays

3 Atmosphere 3

4 Atmosphere layers 4 XR absorbtion UVI absorbtion Gas law+ Heat from below

5 Pressure profile 5

6 Composition 6 Gas % (volume) Nitrogen N Oxygen O Argon Ar Carbon dioxide CO Neon Ne Helium He Methane CH

7 Large scale air transport 7

8 8 Atmospheric cascade What happens to CR in the atmosphere

9 Atmospheric cascade 9 Primary CR particle π π p N p n γ γ μ n N n e - e + e μ N p electromagnetic mesonic nucleonic

10 A cascade simulation 10

11 Cosmic ray measurements 11

12 CR detector = particle detector 12 A particle detector: transfer of (part of) the particle s energy inside the detector into some other form to be easily recorded/detected. The transformation may depend on the type and energy of the particles and the detector s type and design. de/dx Secondary/cascades measurements Magnetic deflections Transition radiation Cherenkov radiation Radio emission Aims to measure: Integral flux energy spectrum Individual particles:» Energy» Mass» Arrival direction

13 What can be observed 13 Elastic scattering of CR particle from nuclei of the detector. Emission of Cherenkov radiation by a particle moving faster than light in matter. Emission of transition radiation produced when a charged particle passes through a boundary of two media with different dielectric properties. Nuclear reactions (inelastic scattering by the strong force) between the CR particle and the detector nuclei. Bremsstrahlung caused by the CR particle in the detector material. This is negligibly small for CR protons or heavier CR particles.

14 14 On the ground Atmosphere itself is a part of the CR detector.

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16 How can it we observe? 16

17 EAS experiments ev» Air showers are absorbed high in the atmosphere: very high altitude needed» Air shower are small : small spacing needed» High fluxes: small areas sufficient At ev» Shower maximum still high in the atmosphere: moderate mountain altitude needed» Moderate detector spacing needed (<100 m)» Rather low fluxes: moderately large areas needed (0.1 km2) At ev» Shower maximum deeper in atmosphere: sea level enough» Low fluxes: areas 1 km 2 needed (detector spacing 150 m) Above ev» Extremely low fluxes: huge area needed ( 1000 km 2 )» Giant showers: spacing 1000 m adequate

18 Galactic cosmic rays: spectrum and fluxes 18 (1 particle per cm 2 -second)

19 First detector 19 Measure of the CRII

20 Ionization chamber 20

21 Geiger counter 21

22 Cloud chamber 22 Expansion cloud chamber. Cloud chambers were combined with magnetic fields to deflect particles (charge studies): (Skobeltzyn 1927)

23 Photoemulsion 23

24 Scintillators 24 The energy loss de/dx is converted into visible light colelcted by a photomultiplier. Scintillators can be inorganic (i.e., iodide, fluoride: NaI CsI BaF2...; liquid noble gases, Ar, Xe...), or organic (hydrocarbon compounds), liquid, or plastic

25 NM 25 Reflector (Paraphine or polyethilene) absorbes slow neutrons but transparent for higher energy n and p. Producer (lead) multiplies neutrons (~10 slow per one fast). Moderator (paraphin or polyethilen) thermalizes neutrons. Proportional Counter (3 kv) (n + 10 B α+ 7 Li)

26 NM network 26

27 Cherenkov light 27 The opening angle alpha is a function of the density of the air and, thus, of the height of emission : cosθ=1/βn MAGIC, the "Major Atmospheric Gamma Imaging Cherenkov

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29 Cosmic-ray induced ionization 29

30 History Theodor Wulf m Theodor Wuld Wuld (German priest) studied ionization by an electroscope (a charge collector) : amount of radiation on the top of Eiffel tower is half of that at the ground (in a cave) radiation from ground

31 CR discovery by CRII : Victor Hess (Nobel Prize 1936) launched an electrometer aboard a balloon to the altitude of 5 km. The ionization rate first decreased till 700 m but then increased with altitude space origin for ionization. It was easy to show that the ionizing radiation was not of solar origin.

32 Domenico Pacini 32 Domenico Pacini Pacini (Assistant at the "Regio Ufficio Centrale di Meteorologia e di Geodinamica ), 1912: ionization 3 m below water is 20% lower than at surface "a sizable cause of ionization exists in the atmosphere originating from penetrating radiation"

33 Atmospheric cascade 33 Primary CR particle π π p N p n γ γ μ n N n e - e + e μ N p electromagnetic mesonic nucleonic

34 Cosmic rays induced ionization: details A) p, 200 MeV 10 6 B) p, 10 GeV 10 7 C) p, 100 GeV Y [sr cm 2 g -1 ] SUM EM MUON HADR Atm. depth [g cm -2 ] Atm. depth [g cm -2 ] Atm. depth [g cm -2 ] OuluCRAC:CRII model

35 Comparison with measurements Q [cm -3 sec -1 atm -1 ]100 Measurements (Readings, Aug 2005) Model (P C =2.5 GV φ=650 MV) P [hpa]

36 CRII: altitude vs. latitude 36 Atm. depth (g/cm 2 ) Geom. latitude (deg) Geom. cutoff (GV) Altitude (km) CRII (cm -3 sec -1 )

37 Spatial distribution of CRII (cm -3 sec -1 ) at 12 km CRII, 200 g/cm

38 SEP effect ( ): anisotropy effect 38 Simulations by the ATMOCOSMIC model (Courtesy L. Desorgher and the U. Bern group)

39 Ionization of the atmosphere 39

40 40 Atmosphere is not plasma Fractional ionization rate ~10-18 sec -1 Degree of ionzation ~10-16 Can we neglect is?

41 41 What happens with the atmosphere in the presence of cosmic rays?

42 Sun Earth relation 42 Direct influence Solar irradiance, variations ~0.1% over a solar cycle Indirect influence IMF G C R S C R

43 CLOUD+SKY experiment 43 Duplissi et al. (2010), Enghoff et al. (2011) A 10-fold increase of ionization (typical changes 25%) 2-fold formation rate, BUT A 10-fold increase in SO2 (typical) 1000-fold formation rate change. Temperature, humidity also affect

44 Jan.2005: stratospheric aerosols 44 Angstrom exponent calculated from SAGE III aerosol extinction as a function of altitude and time in the Northern Polar region (latitude 66 73). Temperature in the same region at 14 km heights

45 Effect of SEP on polar strato. aerosols 45 SEP event GLE % NH effect NH temp SH effect SH temp 2005-Jan YES (strong) Cold YES (weak) Warm 1989-Sep 400 YES (weak) Cold NO Warm 2000-Jul NO Warm Apr NO Warm NO Warm 2003-Oct 50 NO Warm NO Cold The direct effect is weak (Mironova & Usoskin, 2008, 2012, 2013)

46 Climate model simulation (GCR ON-OFF) OFF) 46 Calisto, Usoskin, Rozanov, Thomas, 2011

47 GEC and clouds 47

48 Summary 48 Atmosphere is important for cosmic rays at Earth. Cosmic rays initiate a complicated cascade (shower) in the atmosphere. Cosmic rays form the main source of atmospheric ionization and related physical-chemical changes in the low-mid atmosphere. The direct effect of CR on the atmosphere is very weak. Indirect is unknown.

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