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5th School on Cosmic Rays and Astrophysics, Aug-2012, La Paz, Bolivia.

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High Energy Radiation Phenomena in the Atmosphere

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5th School on Cosmic Rays and Astrophysics La Paz, Bolivia August 22nd to 31st , 2012

High Energy Radiation Phenomena in the AtmospherePart I

Prof. Marcelo A. Leiguide Oliveira

CCNH – UFABC

leigui@ufabc.edu.br


Structure of the Atmosphere

  • The atmosphere is a thin layer of gases:

  • 90,0% (h < 10 km);

  • 99,0% (h < 20 km);

  • 99,9% (h < 30 km);

  • etc.


Atmospheric layers

Troposphere*: 0 – (7 – 18) km

Stratosphere*: 18 – 50 km

Mesosphere: 50 – 80 km

Thermosphere: 80 – 480 km

Exosphere: > 480 km

* most important for CRs physics


Chemical composition of the atmosphere

From Wikipedia


  • Basic concepts of energy transport in the atmosphere:

  • Radiation: energy transfer by electromagnetic waves which takes place in vacuum

  • Conduction: transfer of kinetic energy by collisions of molecules

  • Convection: transport of energy by bulk motion of a fluid


Electromagnetic waves:

  • oscillating electric and magnetic fields that travel in vacuum in the speed of light: c = 299.792.458 m/s ≈ 3 × 108 m/s

  • the electromagnetic spectrum is continuous and we distinguish

  • different types of waves based on bands of frequency or wavelength

  • within each band different processes may

  • occur, leading to different opacities to the waves


Insolation: the amount of solar radiation received at Earth’s surface

The Earth is closest to the Sun on January 3 (perihelion) an farthest from the Sun on July 4 (aphelion)and the revolution axis of the Earth is tilted by 23.5° with respect to the orbital plane, giving rise the seasons, e.g.: winter (summer) in the northern (southern) hemisphere in December.


Annual Heat Inbalances and Convections


Radiation Balance on Earth

  • The Sun is the major source of energy on Earth

  • The incident energy is partially reflected and partially absorbed in the atmosphere

  • The Earth emits energy by blackbody radiation

  • The radiation is partially scattered by air and aerosol molecules


Radiation Balance on Earth

The relevant photons fall into two classes:

Short wavelength (emitted by the Sun): 0.1 < λ < 4.0 µm (ultraviolet, visible and infrared)

Long wavelength (emitted by the Earth’s surface and atmosphere): 4.0 < λ < 100.0 µm (infrared)


Blackbody Radiation


Blackbody Radiation


Blackbody Radiation


Blackbody Radiation


Blackbody Radiation


Blackbody Radiation


Blackbody Radiation


Stefan-Boltzmann law:

Rate at which objects emit radiation is proportional to the fourth power of the temperature

thus the Sun radiates from its photosphere:

more power than the Earth system.


Wien displacement law:


Albedo

average Earth’s albedo ≈ 30%


Radiation Balance (very simple model)


Radiation Balance (very simple model)


Radiation Balance + Greenhouse Effect

The atmosphere is our blanket


Radiation Balance + Greenhouse Effect


Atmospheric Influence on Radiation

  • Upon entering the atmosphere the solar radiation encounters:

  • Gases: atoms and molecules

  • Particles (aerosols): large molecules and dust

  • Clouds: water

and 3 processes may happen:

Scattering

Transmission

Absorption


Atmospheric Scattering

This is the process where an atom or a molecule redirects the energy:

if the outgoing energy (wavelength) is the same: Elastic Scattering

if the outgoing energy (wavelength) is different: Inelastic Scattering

and there may be 3 types of scatterings:

Rayleigh Scattering: by atoms and small molecules

Mie Scattering: by large molecules or aerosols

Non-selective Scattering: by clouds


Rayleigh Scattering

This is the process caused by atoms or small molecules (size < ):

if the outgoing energy (wavelength) is different: Raman Scattering


Rayleigh Scattering

The Rayleigh scattering is nearly isotropic:and is inversely proportional to 4Conclusion: the sky is blue!! … and the sunset is red


Mie Scattering

This is the process caused large molecules & aerosols (size > ):

It is not (hardly) dependent on , but on the size of the particles. The radiation is scattered predominantly in the forward direction.


Rayleigh x Mie Scattering


Non-selective Scattering

This is the process caused by water droplets which are translucent and curved, (acting like lenses) bending and reflecting the light:

the size of water droplets is important, since it will influence on the curvature of the water droplets. Light passing though clouds is an excellent example of non-selective scattering


Transmission

  • Direct passage of light though the atmosphere:

  • on a sunny day, without pollution and water vapor as much as 80% of sunlight may reach the surface

  • as the pollution, water vapor and the amount of clouds increase, the amount of light reaching the surface can drop to zero.


Absorption

Any specie that absorbs solar radiation reducing its intensity while passing through the atmosphere.

Molecular collisions are always occurring and are likely to take place while some of the colliding molecules happens to be in an excited state (due to a previous process) before the reemission. In this case, the excitation is transferred to other kinds of energy: kinetic, rotational, vibrational, ionization …


Absorption

Absorptions don’t occur in the same way for all the wavelengths


Absorption of UV light by stratospheric ozone


Extinction


Size parameter


Radiation Balance on Earth


Recent human activity


And what about the cosmic rays?


And what about the cosmic rays?


5th School on Cosmic Rays and Astrophysics La Paz, Bolivia August 22nd to 31st , 2012

High Energy Radiation Phenomena in the AtmospherePart II

Prof. Marcelo A. Leiguide Oliveira

CCNH – UFABC

leigui@ufabc.edu.br


Electromagnetic Processes

Coulomb scattering


Electromagnetic Processes

Ionization loss


Electromagnetic Processes

Ionization loss


Electromagnetic Processes

Air Fluorescence

Measured fluorescence spectrum in dry air at 800 hPa and 293 K

F Arqueros, F Blanco and J Rosado, New J. Phys. 11 (2009) 065011

AIRFLY Collaboration, Astroparticle Physics, Volume 28, Issue 1, September 2007, Pages 41-57,


Electromagnetic Processes

Cherenkov light


Electromagnetic Processes

Compton scattering


Electromagnetic Processes


Electromagnetic Processes

Inverse Compton Effect


Electromagnetic Processes

Bremsstrahlung


Electromagnetic Processes


Electromagnetic Processes


Electromagnetic Processes


Electromagnetic Processes

Molecular Bremsstrahlung

EAS particles dissipates energy through ionization

A weakly ionized plasma is formed at T ~ 104 K

This plasma cools down very fast (10 ns) though collisions with air molecules

Bremsstrahlung from free electrons (f ~ GHz: microwave band)


Electromagnetic Processes

Synchrotron radiation


Electromagnetic Processes

Radio emission

EAS produces e± in the shower front (2-3 m thick)

These e±bend in the geomagnetic field (~ 0.3 G), generating synchrotron radiation (geosynchrotron)

Emissions for all e± add up coherently

The radiation can be detected by antennas at f ~ 100 MHz (FM band)


Electromagnetic Processes

Pair production


Chemical composition of the atmosphere


Mass Thickness & Depth


Mass Thickness & Depth


5th School on Cosmic Rays and Astrophysics La Paz, Bolivia August 22nd to 31st , 2012

High Energy Radiation Phenomena in the AtmospherePart III

Prof. Marcelo A. Leiguide Oliveira

CCNH – UFABC

leigui@ufabc.edu.br


  • Some EAS arrays:

  • • VolcanoRanch, USA (1959-1962);

  • • Haverah Park, UK (1968-1987);

  • • SUGAR, Australia (1968-1979);

  • • Yakutsk, Russia (1969 -1990);

  • • Akeno, Japan (1980 ++);

  • • AGASA, Japan (1986 ++ );

  • • EASTOP , Italy (1989-1999);

  • • CASA/MIA, USA (1990 ++);

  • • Kascade, Germany (1995 ++);

  • Pierre AugerObservatory, Argentina (2001++).

1994 The AGASA Group in Japan and the Yakutsk group in Russia each reported an event with an energy of 2x1020eV.

Pierre Auger Observatory: taking data since 2004


Cherenkov Radiation in the Atmosphere


  • Some air Cherenkov experiments:

  • CANGAROO, Australia (1992++);

  • CAT, France (1996++);

  • CLUE, CanaryIslands (1997 - 2000);

  • HAGAR Telescope(s), India (2005++);

  • HEGRA, CanaryIslands (1992-2002);

  • HESS, Namibia (HESS-I 2002, HESS-II 2012);

  • MAGIC, CanaryIslands (2003++);

  • VERITAS, USA (2007++);

  • CTA project.

HESS I and HESS-II: four 12 m telescopes andone 28 m telescope

MAGIC: a 17 m telescope

VERITAS: four 12 m telescopes


Cherenkov Radiation in the Atmosphere


Cherenkov Radiation in the Atmosphere


Air Fluorescence Detector

Propagation

Emission

Detection

Fluorescence Radiation


  • Some airfluorescenceexperiments:

  • • Fly’seye/Hires, USA (1981/1999 ++);

  • Pierre AugerObservatory, Argentina (2001++);

  • ASHRA, Hawaii (2002++);

  • Telescope Array (TA), USA (2006++);

  • EUSO, ISS (2016)

1991 The Fly's Eye cosmic ray research group in the USA observed a cosmic ray event with an energy of 3x1020eV.

The Telescope Array

The Pierre Auger Fluorescence Detector


  • Fluorescence track reconstruction

  • monocular mode

  • stereo mode

    issues:

  • - atmospheric transmission

  • - fluorescence yield

  • - Cherenkov subtraction


  • Horizontal attenuation monitors (range ~ 60 km)

  • Steerable LIDARs

  • Laser Shots (Central Laser Facility): light scattering

  • Infrared Monitors (clouds)

  • Cross-checks


  • The fluorescence yield depends on the:

  • wavelength: 34 transitions between 295 and 430 nm (2P and 1N systems)

  • pressure

  • temperature


this event: intial viewing angle 15°, i.e. large direct Cherenkov contribution

iterative procedure, converges in < 4 steps; energy here ~ 2x1018 eV


20 May 2007 E ~ 1019eV


FD: 24 (+3) fluorescence

telescopes (30° x 30° FOV):


  • FD: 24 (+3) fluorescence

  • telescopes (30° x 30° FOV):

  • longitudinal development


TheShower Detector Plane


TheShower Detector Plane


TheShower Detector Plane


  • FD: 24 (+3) fluorescence

  • telescopes (30° x 30° FOV):

  • longitudinal development


  • FD: 24 (+3) fluorescence

  • telescopes (30° x 30° FOV):

  • longitudinal development


  • FD: 24 (+3) fluorescence

  • telescopes (30° x 30° FOV):

  • longitudinal development


  • FD: 24 (+3) fluorescence

  • telescopes (30° x 30° FOV):

  • longitudinal development

  • 10% dutycycle

  • almostcalorimetricmeasurement


S38 (1000)vs. E(FD)

661 hybrid events

J. Abraham etal, Phys. Rev. Lett. 101, (2008) 061101.


Flux calculation:

J. Abraham etal, Phys. Lett. B 685 (2010) 239-246.


A bit of propaganda:


Light pollution in Brazil:


MuchasGracias!

Prof. Marcelo A. Leiguide Oliveira

CCNH – UFABC

leigui@ufabc.edu.br


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