High energy Cosmic Rays trigger Hadronic Showers when they collide with a particle in the Earth’s atmosphere / hydrosphere / lithosphere.
The physical process that cause the propagation of a hadron shower are considerably different from the processes in electromagnetic showers.
About half of the incident hadron energy is passed on to additional secondaries.
The remainder is consumed in multiparticle production of slow pions and in other processes.
The phenomena which determine the development of the hadronic showers are: hadron production, nuclear deexcitation and pion and muon decays.
Neutral pions amount, on average to 1/3 of the produced pions and their energy is dissipated in the form of electromagnetic showers.
Another important characteristic of the hadronic shower is that it takes longer to develop than the electromagnetic one.
This can be seen by comparing the number of particles present versus depth for pion and electron initiated showers.
An atmospheric Hadronic Shower (which includes an Electromagnetic Shower component) may be many kilometres wide.
Cosmic ray study using Air Shower Time coincidence Arrays
G. A. Chelkov, M. A. Demichev, A. S. Zhemchugov
Dzhelepov Laboratory of Nuclear Problems
The electromagnetic component of a Hadronic Shower also produces Cherenkov light.
The original particle arrives with high energy and hence a velocity near the speed of light, so the products of the collisions tend also to move generally in the same direction as the primary, while to some extent spreading sidewise.
In addition, the secondary particles produce a widespread flash of light in forward direction due to the Cherenkov effect, as well as fluorescence light that is emitted isotropically from the excitation of nitrogen molecules.
The particle cascade and the light produced in the atmosphere can be detected with surface detector arrays and optical telescopes.
Surface detectors typically use Cherenkov detectors or Scintillation counters to detect the charged secondary particles at ground level.
The telescopes used to measure the fluorescence and Cherenkov light use large mirrors to focus the light on PMT clusters.
Cherenkov light is usually described as “blue” or “brilliant blue” light.
Unlike fluorescence or emission spectra that have characteristic spectral peaks, Cherenkov radiation is continuous.
Around the visible spectrum, the relative intensity per unit frequency is approximately proportional to the frequency. That is, higher frequencies (shorter wavelengths) are more intense in Cherenkov radiation.
This is why visible Cherenkov radiation is observed to be brilliant blue.
In fact, most Cherenkov radiation is in the ultraviolet spectrum—it is only with sufficiently accelerated charges that it even becomes visible; the sensitivity of the human eye peaks at green, and is very low in the violet portion of the spectrum.
Each “flash” of Cherenkov light lasts only a couple of nanoseconds but there are subsequent “flashes” as the secondary particles cascade.
Cherenkov light generated in the atmosphere by heavy nuclei among cosmic rays: while traversing the atmosphere, the nucleus radiates “direct” Cherenkov light.
Then, it interacts and generates a cascade of secondary particles, a particle shower.
These secondary particles in turn emit Cherenkov light.
Since the opening angle of the Cherenkov cone – the “beam width” – is governed by the refractive index of air and hence by the air density, the Cherenkov light emitted by the primary nucleus high up in the atmosphere is more beamed than the light from the air shower.
Also, the shower particles, due to their lower energy, are more strongly deflected along their path, further widening the distribution of light.
A telescope placed at the right location on the ground – about 100 m from the trajectory of the primary particle – will detect both components of Cherenkov light.
HESS – High Energy Stereoscopic System
Each “flash” of Cherenkov light is associated with spallation which is “a form of naturally occurring nuclear fission and nucleosynthesis”.
Cosmic ray spallation is a form of naturally occurring nuclear fission and nucleosynthesis.
It refers to the formation of elements from the impact of cosmic rays on an object.
The secondary fast nucleons (and minor mesonic flux) continue to produce cosmogenic nuclides in the atmosphere, hydrosphere, and lithosphere by breaking apart target atoms through spallation interactions.
As energy is lost due to successive reactions, down to the 1 to 5 MeV range, the neutrons are no longer capable of causing spallation reactions and their remaining energy is dissipated mainly by momentum transfer during elastic scattering off incident nuclei.
TCN – Terrestrial In Situ Cosmogenic Nuclides.
J.C. Gosse and F.M. Phillips, 2001
Quaternary Science Reviews 20(14), 1475-1560.
Thus, each “flash” of Cherenkov light is associated with the creation of a cosmogenic isotope.
Cosmogenic nuclides (or cosmogenic isotopes) are rare isotopes created when a high-energy cosmic ray interacts with the nucleus of an in situ solar system atom, causing cosmic ray spallation.
These isotopes are produced within earth materials such as rocks or soil, in Earth’s atmosphere, and in extraterrestrial items such as meteorites.
By measuring cosmogenic isotopes, scientists are able to gain insight into a range of geological and astronomical processes.
There are both radioactive and stable cosmogenic isotopes.
Some of these radioisotopes are tritium, carbon-14 and phosphorus-32.
And each “flash” of Cherenkov light is associated with the creation of ionizing radiation.
NAIRAS – Nowcast of Atmospheric Ionizing Radiation System
The strange world of Cosmic Ray science clearly realises [see below] that energy is being transformed in the interstellar medium and Earth’s atmosphere.
That bath of ancient and young photons suffusing the Universe today is called the extragalactic background light (EBL).
An accurate measurement of the EBL is as fundamental to cosmology as measuring the heat radiation left over from the Big Bang (the cosmic microwave background) at radio wavelengths.
Comparing the calculations of the unattenuated gamma rays to actual measurements of the attenuation of gamma rays and X-rays from blazars at different distances allowed Dominquez et al. to quantify the evolution of the EBL—that is, to measure how the EBL changed over time as the Universe aged—out to about 5 billion years ago (corresponding to a redshift of about z = 0.5).
“Five billion years ago is the maximum distance we are able to probe with our current technology,” Domínguez said.
Detection of the Cosmic Gamma Ray Horizon
Measures all the Light in the Universe since The Big Bang
University of California
Published online May 24, 2013, in The Astrophysical Journal
Unfortunately, this knowledge of the Cosmic Ray Blues isn’t transformed into enlightenment because the settled scientists prefer the rich pickings of the Big Bang Boogie.