cosmic rays

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cos·mic rays

high-velocity particles of enormous energies, bombarding earth from outer space; the "primary radiation" consists of protons and more complex atomic nuclei that, on striking the atmosphere, give rise to neutrons, mesons, and other less energetic "secondary radiation."


(ra) [Fr. rai, raie, fr L. radius, ray]
1. Any of several lines diverging from a common center.
2. A line of propagation of any form of radiant energy, esp. light or heat; loosely, any narrow beam of light.

actinic ray

A solar ray capable of producing chemical changes. Synonym: chemical ray

alpha ray

A ray composed of positively charged helium particles derived from atomic disintegration of radioactive elements. Its velocity is one tenth the speed of light. Alpha rays are completely absorbed by a thin sheet of paper and possess powerful fluorescent, photographic, and ionizing properties. They penetrate tissues less than beta rays.

beta ray

A ray composed of negatively charged electrons expelled from atoms of disintegrating radioactive elements.
Synonym: beta particle

border ray

Grenz ray.

cathode ray

A ray composed of negatively charged electrons discharged by a cathode through a vacuum, moving in a straight line and producing x-ray photons upon hitting solid matter.

central ray

The theoretical center of an x-ray beam. The term designates the direction of the x-ray photons as projected from the focal spot of the x-ray tube to the radiographical film.

characteristic ray

A secondary photon produced by an electron giving up energy as it changes location from an outer to an inner shell in an atom. The wavelengths are characteristic of the difference in binding energies.

chemical ray

Actinic ray.

cosmic rays

Cosmic radiation.

delta rays

Highly penetrative waves emitted by radioactive substances.

erythema-producing ray

Ultraviolet radiation (wavelengths between 2050 and 3100 A.U.) capable of reddening skin.

gamma rays

Short wavelength, high-energy electromagnetic radiation emitted by disintegrating atomic nuclei.

grenz ray

A low-energy x-ray photon with an average wavelength of 2 A.U. (range from 1 to 3 A.U.); obtained with peak voltage of less than 10 kV. Grenz rays lie between ultraviolet and x-rays.
Synonym: border ray

hard ray

An x-ray photon of short wavelength and great penetrative power.

heat ray

Radiation whose wavelength is between 3,900 and 14,000 A.U. Shorter wavelength heat sources penetrate tissues better than longer (infrared) sources.
See: heat

infrared ray

An invisible heat ray from beyond the red end of the spectrum. Infrared wavelengths range from 7700 angstrom units (A.U.) to 1 mm. Long-wave infrared rays (15,000 to 150,000 A.U.) are emitted by all heated bodies and exclusively by bodies of low temperature such as hot water bottles and electric heating pads; short-wave infrared rays (7,200 to 15,000 A.U.) are emitted by all incandescent heaters. The sun, electric arcs, incandescent globes, and so-called infrared burners are sources of infrared rays.


Infrared ray energy is transformed into heat in a superficial layer of the tissues. It is used therapeutically to stimulate local and general circulation and to relieve pain. The infrared thermograph is useful in studying the heat of tissues. See: radiation; thermography

luminous ray

One of the visible rays of the spectrum.

medullary ray

In the kidney, one of many slender processes composed of one or two collecting ducts and other straight tubules that project into the cortex from the bases of renal pyramids.

monochromatic ray

Single wavelength electromagnetic radiation.

pigment-producing ray

A ray between 2540 and 3100 A.U. that is most effective in stimulating pigment production in the skin. This is due to a local response to irritation of cutaneous prickle cells.

positive ray

A ray composed of positively charged ions that in a discharge tube moves from the anode toward the cathode.

primary ray

In radiographic imaging, the x-ray beam that originates at the source of radiation. It is usually used to differentiate those rays from the additional scatter radiation that constitutes the majority of the beam used to create images.

roentgen ray

X-ray photon.

scattered ray

See: radiation

secondary rays

X-ray photons produced after the incoming, primary x-ray photons remove an inner-shell electron from the atom. Secondary rays can also be primary x-rays that have been diverted through scatter interactions with other atoms. Secondary rays are of lower energy than primary rays and are usually absorbed in matter, an interaction that produces x-ray photons via a cascade effect.

ultraviolet ray

An invisible ray of the spectrum beyond the violet rays. The wavelengths of ultraviolet rays vary. They may be refracted, reflected, and polarized, but will not traverse many substances impervious to the rays of the visible spectrum. They rapidly destroy the vitality of bacteria, and are able to produce photochemical and photographic effects.

cosmic rays

a stream of atomic particles entering the earth's atmosphere from outer space at nearly the speed of light. Cosmic rays are thought to be a cause of SPONTANEOUS MUTATIONS.

cosmic rays

ionizing irradiation from outer space bombarding the earth and its atmosphere. They contribute to the background radiation that is always present at the earth's surface.
References in periodicals archive ?
At locations both in and outside of Japan, ICRR has conducted research on high-energy cosmic rays, high-energy gamma rays, and neutrinos; for example, the Super-Kamiokande(5) Project has discovered neutrino oscillations and the Tibet AS-gamma Experiment used cosmic rays to observe the sun's cosmic-ray shadow(6).
7 AU from the Sun, sudden and unprecedented intensity changes were observed in anomalous and galactic cosmic rays.
This means predicting future global warming and sea level rise is not simple, since it also significantly depends on the unpredictability of cosmic ray intensity.
A gamma-spectrometer with a scintillation detector was used to measure hard cosmic ray flux (HCRF) ([TEXT NOT REPRODUCIBLE IN ASCII] 1984; [TEXT NOT REPRODUCIBLE IN ASCII] 1988).
Galactic cosmic rays are highly energetic particles, originating from unknown sources outside our solar system and hitting the Earth's surface at an extremely high speed.
Astrophysicists from the California Institute of Technology enlisted help from San Fernando Middle School students Wednesday in the tracking of cosmic rays - an ambitious quest to further unravel mysteries of the universe.
Our main goal is to understand the origins of these rare cosmic rays, in order to gain a better understanding of some of the most violent processes shaping the universe.
In their attempt to quantify the effect that solar activity-whether directly or through osmic rays-may have had on global temperatures in the twentieth century, Sloan and Wolfendale compared data on the rate of cosmic rays entering the atmosphere, which can be used as a proxy for solar activity, with the record of global temperatures going back to 1955.
But in contrast, CRE theory says cosmic rays - energy particles originating in space - play the dominant role in breaking down ozone-depleting molecules and then ozone.
This discovery is a major step toward understanding the origin of cosmic rays, one of Fermi's primary mission goals.
These record what happens when cosmic ray particles smash into atmospheric molecules.
A prominent theory holds that this breakdown is sparked by a cosmic ray, part of the constant rain from space, striking an air molecule and kicking out a high- speed electron left in the atmosphere after a normal lightning bolt.