An
air shower is an extensive (many kilometres wide)
cascadeIn particle physics, a shower is a cascade of secondary particles produced as the result of a high-energy particle interacting with dense matter. The incoming particle interacts, producing multiple new particles with lesser energy; each of these then interacts in the same way, a process that...
of ionized particles and
electromagnetic radiationElectromagnetic radiation is a ubiquitous phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It consists of electric and magnetic field components which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation...
produced in the
atmosphereThe Earth's atmosphere is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
when a
primary cosmic rayCosmic rays are energetic particles originating from outer space that impinge on Earth's atmosphere. Almost 90% of all the incoming cosmic ray particles are protons, almost 10% are helium nuclei , and slightly under 1% are heavier elements and electrons...
(i.e. one of extraterrestrial origin) enters the atmosphere. The term
cascade means that the incident particle, which could be a
protonThe proton is a subatomic particle with an electric charge of +1 elementary charge. It is found in the nucleus of each atom but is also stable by itself and has a second identity as the hydrogen ion, H
+...
, a
nucleusThe nucleus is the very dense region consisting of nucleons at the center of an atom. Almost all of the mass in an atom is made up from the protons and neutrons in the nucleus, with a very small contribution from the orbiting electrons....
, an
electronAn electron is a subatomic particle that carries a negative electric charge. It has no known substructure and is believed to be a point particle. An electron has a mass that is approximately 1836 times less than that of the proton. The intrinsic angular momentum of the electron is a half integer...
, or (rarely) a
positronThe positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1, a spin of , and the same mass as an electron. When a low-energy positron collides with a low-energy electron, annihilation occurs, resulting in the production...
strikes an atom in the air so as to produce many high
energyIn physics, energy is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law...
ions (
secondaries), which in turn create more, and so on.
Discussion
Ask a question about 'Air shower (physics)' Start a new discussion about 'Air shower (physics)' Answer questions from other users |
An
air shower is an extensive (many kilometres wide)
cascadeIn particle physics, a shower is a cascade of secondary particles produced as the result of a high-energy particle interacting with dense matter. The incoming particle interacts, producing multiple new particles with lesser energy; each of these then interacts in the same way, a process that...
of ionized particles and
electromagnetic radiationElectromagnetic radiation is a ubiquitous phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It consists of electric and magnetic field components which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation...
produced in the
atmosphereThe Earth's atmosphere is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
when a
primary cosmic rayCosmic rays are energetic particles originating from outer space that impinge on Earth's atmosphere. Almost 90% of all the incoming cosmic ray particles are protons, almost 10% are helium nuclei , and slightly under 1% are heavier elements and electrons...
(i.e. one of extraterrestrial origin) enters the atmosphere. The term
cascade means that the incident particle, which could be a
protonThe proton is a subatomic particle with an electric charge of +1 elementary charge. It is found in the nucleus of each atom but is also stable by itself and has a second identity as the hydrogen ion, H
+...
, a
nucleusThe nucleus is the very dense region consisting of nucleons at the center of an atom. Almost all of the mass in an atom is made up from the protons and neutrons in the nucleus, with a very small contribution from the orbiting electrons....
, an
electronAn electron is a subatomic particle that carries a negative electric charge. It has no known substructure and is believed to be a point particle. An electron has a mass that is approximately 1836 times less than that of the proton. The intrinsic angular momentum of the electron is a half integer...
, or (rarely) a
positronThe positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1, a spin of , and the same mass as an electron. When a low-energy positron collides with a low-energy electron, annihilation occurs, resulting in the production...
strikes an atom in the air so as to produce many high
energyIn physics, energy is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law...
ions (
secondaries), which in turn create more, and so on. The original particle having arrived with high
energyIn physics, energy is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law...
and hence
velocityIn physics, velocity is the rate of change of position. It is a vector physical quantity; both speed and direction are required to define it. In the SI system, it is measured in meters per second: or ms-1. The scalar absolute value of velocity is speed...
near the
speed of lightIn physics, the speed of light is a physical constant, the speed at which electromagnetic radiation, such as light, travels in free space . Its value is 299,792,458 metres per second...
, the products of the collisions tend also to move generally downward, while to some extent spreading sidewise. The overall effect, when the
energyIn physics, energy is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law...
of the primary is high enough, is to produce a widespread flash of light due to the Cherenkov effect, and to excitation of air molecules. This can be detected with arrays of mirrors and photocells. The actual arrival of the cascade of particles can also be detected in many cases, also generally with detectors based on the Cherenkov effect.
External links
- Extensive Air Showers.
- Buckland Park Air Shower Detector
- Haverah Park Detection System
- HiRes Detector System (current, 2004)
- Pierre Auger Observatory
- AIRES (AIRshower Extended Simulations) : Large and well documented Fortran package for simulating cosmic ray showers by Sergio Sciutto at the Department of Physics of the Universidad Nacional de La Plata
The National University of La Plata is an Argentine national university and the most important one situated in the city of La Plata, capital of Buenos Aires Province...
, Argentina
- CORSIKA
CORSIKA is a physics computer software for simulation of extensive air showers induced by high energy cosmic rays. It may be used up to and beyond the highest energies of 100 EeV....
, CORSIKA: Another code for simulating cosmic ray air showers by Dieter Heck of the Forschungszentrum KarlsruheForschungszentrum Karlsruhe [in der Helmholtz-Gemeinschaft]is a research institution based in Karlsruhe/BW, Germany...
, Germany
- COSMUS : Interactive animated 3d models of several different cosmic ray air showers, and instructions on how to make your own using AIRES simulations. From the COSMUS group at the University of Chicago.
- Milagro Animations : Movies and instructions for how to make them, showing how air showers interact with the Milagro detector. By Miguel Morales.
- CASSIM Animations : Animations of different cosmic ray air showers by Hajo Dreschler of New York University.