Rays, cosmic

Particles, approaching from all directions, with relativistic energies and mass, known as cosmic rays, constitute a potentially important source of astrophysical data. Primary cosmic rays consist almost entirely of fully ionized atomic nuclei in abundancies that differ significantly from the solar abundances of 

The major component of cosmic rays is relativistic protons, which, not surprisingly, are accompanied by an equivalent amount of relativistic electrons. When such fast electrons move in a magnetic field, as in a synchrotron, they emit electromagnetic radiation at a frequency proportional to the magnetic field strength. This fact has been used to associate the isotropic radiofrequency radiation, which arrives from the Milky Way, to an interstellar magnetic field that pervades the Galaxy. 

Another, linearly polarized, radio source in the Crab nebula, where a supernova explosion was observed in the year 1054, leaving behind a pulsating neutron star, could be of similar origin as the radiation in the Milky Way. The likelihood that the pulsar drives the acceleration of both relativistic electrons and of cosmic rays could imply that most cosmic rays in the Galaxy are also 

The origin of X-rays, 7-ray bursts and radiowaves that pervade the Galaxy is as mysterious as the cosmic-ray sources. Evidence is mounting that in most cases these phenomena are linked to violent explosions, thought to include neutron-star quakes, quark nuggets, supernovae, matter-antimatter annihilation, clumping of quasars and colliding stars. Of all space radiations radio phenomena have been studied in most detail. 

It has been discovered rather recently that there is a very penetrating kind of radiation in the atmosphere which seems to be coming in from outside. This radiation has been called cosmic rays, and since it has new and interesting properties a brief account of them will be given here. 

This radiation can be detected and its intensity measured by means of the electrical conductivity which it produces in air and other gases. An electroscope suitable for measuring such conductivity is shown in Fig. 22. 

If some radium is brought near the cylinder, the penetrating radiation from the radium makes the gas conduct, and the fibers move together. The penetrating radiation from 

The gamma ray photons passing through the gas in the cylinder knock electrons out of some of the atoms and these electrons have enough energy to knock electrons out of a great many more atoms. 

If the fibers are positively charged they attract the free electrons which move on to the fibers and neutralize the positive charge. The gas is then said to be conducting. 

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As cosmic rays pass through the upper atmosphere, some of the present is converted to by the capture of high-energy neutrons. The then migrates into... 

Origin. Typical meteorites have formation ages of 4.55 Gyr and exposure ages of only 10 years, duting which time they existed as meter-sized bodies unshielded to the effects of cosmic rays. With the exception of the SNC (Martian) and lunar meteorites it is widely befleved that most conventional... 

Extraterrestrial dust particles can be proven to be nonterrestrial by a variety of methods, depending on the particle si2e. Unmelted particles have high helium. He, contents resulting from solar wind implantation. In 10-)J.m particles the concentration approaches l/(cm g) at STP and the He He ratio is close to the solar value. Unmelted particles also often contain preserved tracks of solar cosmic rays that are seen in the electron microscope as randomly oriented linear dislocations in crystals. Eor larger particles other cosmic ray irradiation products such as Mn, Al, and Be can be detected. Most IDPs can be confidently distinguished from terrestrial materials by composition. Typical particles have elemental compositions that match solar abundances for most elements. TypicaUy these have chondritic compositions, and in descending order of abundance are composed of O, Mg, Si, Ee, C, S, Al, Ca, Ni, Na, Cr, Mn, and Ti. 

However, reaction 7 suffers other shortcomings, eg, entropy problems. Other proposals range from trace peroxidic contaminants to ionic mechanisms for generating peroxides (1) to cosmic rays (17). In any event, the initiating reactions are significant only during the induction period (18). 

However, it is produced in the upper atmosphere by cosmic rays (18,19). 

There is a very low cosmic abundance of boron, but its occurrence at all is surprising for two reasons. First, boron s isotopes are not involved in a star s normal chain of thermonuclear reactions, and second, boron should not survive a star s extreme thermal condition. The formation of boron has been proposed to arise predominantly from cosmic ray bombardment of interstellar gas in a process called spallation (1). 

Tritium [15086-10-9] the name given to the hydrogen isotope of mass 3, has symbol or more commonly T. Its isotopic mass is 3.0160497 (1). Moletecular tritium [10028-17-8], is analogous to the other hydrogen isotopes. The tritium nucleus is energetically unstable and decays radioactively by the emission of a low-energy P particle. The half-life is relatively short (- 12 yr), and therefore tritium occurs in nature only in equiUbrium with amounts produced by cosmic rays or man-made nuclear devices. 

Tritium has also been observed in meteorites and material recovered from sateUites (see also Extraterrestrial materials). The tritium activity in meteorites can be reasonably well explained by the interaction of cosmic-ray particles and meteoritic material. The tritium contents of recovered sateUite materials have not in general agreed with predictions based on cosmic-ray exposure. Eor observations higher than those predicted (Discoverer XVII and sateUites), a theory of exposure to incident tritium flux in solar flares has been proposed. Eor observations lower than predicted (Sputnik 4), the suggested explanation is a diffusive loss of tritium during heating up on reentry. 

Cosmogenic radionuclides are formed in the upper atmosphere by the interaction of cosmic rays, primarily from the sun, with elements present in the atmosphere (e.g. 0, and " Ar). Their half-lives range from months to... 

Everyone receives small radiation doses every day Figure 8.3-5 illustrates some of the doses received from background and other types of radiation. Note that the scale is logarithmic , and that background and cosmic-ray doses vary over an order of magnitude just with location and elevation. In addition to these natural sources, most people receive some medical and dental doses each year. 

Electromagnetic radiation (Section 13.1) Various forms of radiation propagated at the speed of light. Electromagnetic radiation includes (among others) visible light infrared, ultraviolet, and microwave radiation and radio waves, cosmic rays, and X-rays. 

Though measurements of solar output have been taken only for the past eighteen years, longer trend patterns can be derived from indirect data sources, such as ice cores and tree rings. Cosmic rays, which fluctuate with the sun s activity, also strike constituents of the atmosphere, creating radioactive versions of certain elements. Beiyllium, in particular, is ionized to "Be by cosmic rays. The "Be then gets incorporated into trees as they grow, and is trapped in bubbles in ice masses, as is carbon dioxide. 

Earth and the sun, and, as far as is kno wn, the stars and planets in the rest of the visible universe, are made of ordinai y matter. However, according to a theoi y fir.st proposed by Paul Dirac in 1928, for every kind of particle of ordinary matter that exists in nature, there can exist an antiparticle made of antimatter. Some antiparticles have been discovered for example, the antiparticle of the electron, called the positron, was discovered in 1932 in cosmic rays falling on earth and have also been created in experiments performed in the laboratory. Antimatter is very simi-... 

Carbon-12 is the principal isotope of carbon, but a small proportion of carbon-14 is present in all living organisms. Its nuclei are produced when nitrogen nuclei in the atmosphere are bombarded by neutrons formed in the collisions of cosmic rays with other nuclei ... 

Most CO and CO2 in the atmosphere contain the mass 12 isotope of carbon. However, due to the reaction of cosmic ray neutrons with nitrogen in the upper atmosphere, C is produced. Nuclear bomb explosions also produce C. The C is oxidized, first to CO and then to C02 by OH- radicals. As a result, all CO2 in the atmosphere contains some 0, currently a fraction of ca. 10 of all CO2. Since C is radioactive (j -emitter, 0.156 MeV, half-life of 5770 years), all atmospheric CO2 is slightly radioactive. Again, since atmospheric CO2 is the carbon source for photos5mthesis, aU biomass contains C and its level of radioactivity can be used to date the age of the biological material. 

At the top of the atmosphere, more properly at altitudes where the density is sufficiently low, high-energy cosmic ray particles cause nuclear chemical reactions with important products. The production of radioactive (or radiocarbon) already has been mentioned. 

Other radioisotopes known to be produced by cosmic rays include Be, H, Na, Be, and Of these Be, P, and P have activities that are high enough to be measured in rainwater. In several instances, notably 0 and Be, these radioactive elements are useful as tracers. 

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