(very-high-energy particles from beyond the solar system)
Cosmic rays are high energy particles,
typically with energies distributed around
0.3 GeV (4.8 × 10-11 joule),
but the highest energy have been
up to 3 × 1011 GeV.
The term cosmic ray was coined when detectors were developed
that demonstrate they continually fall on Earth,
and the term traditionally included photons.
However, common astrophysics usage has come to use EMR
terminology for such photons, and reserve the term cosmic ray
for other particles, including protons,
heavier nuclei (such as alpha particles)
electrons, with other particles such as neutrinos
sometimes included when they have similar energies.
They are theorized to be formed largely by supernovae.
Cosmic rays are continually arriving, i.e.,
as the cosmic ray background (CRB), but that phrase is not commonly
used perhaps because all known cosmic rays fit that description.
Some classes of cosmic-ray particles by kinetic energy (KE):
- solar cosmic rays or SCRs, under 10 GeV - at this energy, presumed to be from the Sun; basically the same as solar energetic particles.
- galactic cosmic rays or GCRs, i.e., 10 GeV to 1015 eV - ubiquitous and presumed to be from within the Milky Way.
- extragalactic cosmic rays (occasionally EGCRs) - above the GCR maximum, presumed to be from beyond the Milky Way.
- VHE cosmic rays or VHECRs or very-high energy cosmic rays - above 100 GeV.
- UHE cosmic rays or UHECRs or ultra-high energy cosmic rays - above 1018 eV (not the same threshold used for ultra-high-energy gamma rays (UHEGR)).
- EE cosmic rays or EECRs or extreme energy cosmic rays - above the GZK limit, i.e., 50 million TeV or 5 × 1019 eV.
A famous graph, the Swordy plot demonstrates
that cosmic rays occur basically
with a power law spectrum over a wide range.
Particles approaching Earth (i.e., before the effects of the
atmosphere) arrive rates of roughly a 1-GeV particle per square
meter per three hours falling such that there's roughly a 10-PeV particle
per square meter every four months.
Cosmic ray astronomy makes use of space-based observatories
such as INTEGRAL, and ground detectors such as LOPES,
and Milagro. At high energies, the type of particle is often
not evident, merely the KE, and the abundances of proton
cosmic ray particles versus heavier nuclei or other particles at
particular energies is of research interest. There is something
of an assumption that they are protons, without evidence to the
Referenced by pages:
Advanced Composition Explorer (ACE)
anomalous cosmic rays (ACR)
black hole (BH)
cosmic background radiation (CBR)
electron volt (eV)
Fenton Hill Observatory (FHO)
gamma rays (GR)
high-energy astrophysics (HEA)
Lunar Reconnaissance Orbiter (LRO)
Orbiting Wide-angle Light Collectors (OWL)
Pierre Auger Observatory (PAO)
solar energetic particle (SEP)
Telescope Array Project (TA)
tau neutrino (ντ)
Van Allen belts