Cosmic Rays Particle Physics Gaisser Pdf Files
- Since the 1970s, particle physicists have described. COSMIC RAYS AND ELEMENTARY PARTICLE PHYSICS View the table of contents for this issue, or go to the journal homepage for more. Gaisser) cosmic rays and particle physics. Cosmic rays and particle physics by gaisser. Cosmic rays and particle physics gaisser pdf Mirror Link #1.
- Cosmic rays are high energy charged particles, originating in outer space, that travel at nearly the speed of light and strike the Earth from all directions. Most cosmic rays are the nuclei of atoms, ranging from the lightest to the heaviest elements in the periodic table. Cosmic rays also include high energy electrons, positrons, and other.
The intent is to keep the book up-to-date. Many-body theory is a field which continually evolves in time. Journals only publish new results, conferences only invite speakers to report new phenomena, and agencies only fund scientists to do new physics. Today's physics is old hat by tomorrow.
Photosynthesis is a mechanism developed by terrestrial life to utilize the energy from photons of solar origin for biological use. Subsurface regions are isolated from the photosphere, and consequently are incapable of utilizing this energy. This opens up the opportunity for life to evolve alternative mechanisms for harvesting available energy. Bacterium Candidatus Desulforudis audaxviator, found 2.8 km deep in a South African mine, harvests energy from radiolysis, induced by particles emitted from radioactive U, Th and K present in surrounding rock. Another radiation source in the subsurface environments is secondary particles generated by galactic cosmic rays (GCRs).
Using Monte Carlo simulations, it is shown that it is a steady source of energy comparable to that produced by radioactive substances, and the possibility of a slow metabolizing life flourishing on it cannot be ruled out. Two mechanisms are proposed through which GCR-induced secondary particles can be utilized for biological use in subsurface environments: (i) GCRs injecting energy in the environment through particle-induced radiolysis and (ii) organic synthesis from GCR secondaries interacting with the medium. Laboratory experiments to test these hypotheses are also proposed. Implications of these mechanisms on finding life in the Solar System and elsewhere in the Universe are discussed. 1. Introduction Radiation in the form of photons is the primary way by which solar energy is transferred to living systems. The energy of a typical photon is between 2 and 3 eV (visible red, 1.8 eV and visible blue, 3.1 eV), and an abundant supply of such photons makes it convenient for life to utilize it for metabolic purposes. Even though most of the energy is lost in heat, the overall efficiency of 0.1–8% is sufficient to power metabolism.
Studies of ionizing radiation, on the other hand, have mostly been associated with health-effects on humans , and studies of radiation resistance on microbes ,. By definition, ionizing radiation has the energy to ionize, or to eject at least one electron from a neutral atom or a molecule, which is 13.6 eV for a neutral hydrogen atom, for example. Ionizing radiation can interact with DNA and cause reparable or irreparable damage, depending on the type and energy of the radiation. Such damages have the potential to modify the genetic code through mutations, alter the way DNA functions, and transfer mutations to the next generation(s) ,.
Radiation damage can also cause cancer as seen in a number of studies with ultraviolet (UV) and particle interactions with humans, primarily in context of oncological studies, nuclear accidents and astronaut health in outer space –. Nevertheless, a high dosage of ionizing radiation can force organisms to develop mechanisms that enable them to survive in extreme conditions. Geochemical processes are well known to support subsurface life ,. An important shift in our understanding came about when studies revealed that subsurface life can be independently supported by radiolysis, where the source of radiation is particles emitted from the decay of radioactive substances ,.
Radioactive materials present deep underground produce secondary particles such as alpha, beta and gamma radiation. Secondary particles interact with the environment and provide energy for chemical change. Organisms can use these particles indirectly for metabolic purposes. Candidatus Desulforudis audaxviator is such an example, which thrives in a radiolysis-powered ecosystem ( a). Radiation from radioactive rock dissociates H 2O into a number of radicals, useful for biological reactions.
It is able to extract carbon from dissolved CO 2 and nitrogen in the form of ammonia from the rock, and utilize them to synthesize amino acids. Such an organism can potentially thrive in subsurface environments on Mars, Moon, Europa or other planetary systems in the presence of radioactive substances. ( a) A colony of Ca. Audaxviator, discovered in a 2.8 km deep gold mine near Johannesburg, South Africa. (public domain), via Wikimedia Commons.
( b) Transmission electron. Candidatus D. Audaxviator thrives in a 2.8 km deep South African gold mine ,. A comprehensive analysis on the availability of nuclear power for deep surface microbes has also been done. Radiolytic dissociation of water due to radiogenic decay of U, Th and K in rock produces a number of radicals, and generates molecular hydrogen (H 2), along with other biologically useful products.
Radiolytically generated chemicals provide the necessary energy and nutrients to the system, sulfate reduction is the dominant electron-accepting process and H 2 and formate are primary electron donors. These provide the energy to sustain a minimal metabolism.
A part of the energy is also utilized to repair damage caused by ionizing radiation. Studies have shown that H 2 produced through geochemical processes can also be utilized for metabolism, independent of photosynthesis, using similar mechanisms. In the light of these findings, it is reasonable to propose that instead of or in addition to in situ energy sources, the radiation (potentially supporting radiolysis-based life) can be of cosmic origin. Galactic cosmic rays (GCRs) are charged particles, mostly protons, originating beyond the Solar System –.
They have relatively lower flux but possess much higher energy than other radiation sources on Earth, and have noteworthy biological effects on terrestrial life and possibly on extrasolar planets –. Upon interaction with a planetary atmosphere or surface, GCRs produce a cascade of secondary particles that include electrons, positrons, gamma rays, neutrons and muons. Muons can travel several kilometres deep below the surface depending on their energy ,. These secondary particles can induce radiolysis and as described later, possibly power a subsurface ecosystem. Galactic cosmic ray-induced radiolysis As discussed in the previous section, radioactive rocks provide an in situ production source of energy for subsurface life.
A similar mechanism is proposed in this section. However, the energy source considered here is extraterrestrial. For planets with substantial atmospheres, the primary GCR particles strike the atmosphere and produce a cascade of secondary particles, also referred to as an air shower. If a planet lacks an atmosphere, particles are able to directly strike the surface and the cascade of secondary particles is able to propagate underground. The secondary particles produced in the cascade, such as pions and kaons, are highly unstable, and quickly decay to other particles including beta particles (electrons and positrons) and gamma rays. It must be noted that beta particles and gamma rays are also produced during radioactive decay in underground rock.
When charged pions decay muons are produced, and these can travel several kilometres deep depending on their energy. It should be emphasized that all types of charged particles such as electrons and positrons can contribute to radiolysis in regions near the surface, but muons become important at greater depths where the flux of other particles becomes nearly zero. They only undergo electromagnetic interactions and lose 2–8 MeV energy per gram per square centimetre in the material they traverse.
The energy loss is a combination of ionization, bremsstrahlung, pair production and inelastic nuclear scattering. Energetic particles are capable of destroying organic materials present in the surface or subsurface environment of planets with thin atmospheres. A number of studies have been devoted to studying the impact of GCRs on the possible destruction of organic matter on Mars –.
Mars' surface radiation dose is several orders of magnitude higher than that of the Earth due to its thin atmosphere. Exposure to high environmental radiation dose also leads to substantial energy expenditure in repairing radiation-induced damage. Bacterium Deinococcus radiodurans is the focus of numerous studies and is the most radioresistant microbe with a lethal dose (LD10) at 15 kGy ( b). Deinococcus radiodurans has a specialized recombination system for DNA repair from ionizing radiation. Interestingly, many fungal species also have very high radiation resistance. Many fungi have 10% survival chance or LD10 values exceeding 5 kGy.
Other species, such as Ustilago maydis are also known to have extreme radiation resistance but have a different mechanism to cope with compared with radiation D. For comparison, mammals have very low radiation resistance and a dose between 5 and 10 Gy is lethal. It has been found that the action of proteins is primarily responsible for the repair mechanism. An abundance of highly melanized fungal spores in the early Cretaceous period deposits has been uncovered, where other plant and animal species have died out. These types of fungi can be found in high-altitude terrains, Arctic and Antarctic regions, and in the Evolution Canyon in Israel. Radiotropism is a term used to describe the growth of fungi from exposure to radionuclides.
Most radionuclides emit beta (electrons and positrons) and gamma (photons) radiation and studies have shown that exposure to both sources promoted directional growth of fungi. Exposure to 121Sn and 137Cs sources showed that the spore germination in species increased considerably, a phenomenon also known as ‘radiostimulation’. The presence of several microorganisms has been studied in the Russian Mir Space Station as well as the International Space Station. The organisms consist of both bacteria and fungi, and are exposed to about 4 cGy of ionizing radiation per year. Many bacteria and fungi in these environments have been found to be pigmented or melanized. Dadachova et al.
Concluded that ionizing radiation changed the electron spin resonance signal of melanin, making it more efficient in acting as an ionizing radiation transducer. Experiments have shown increased metabolic activity in melanized Cryptococcus neoformans relative to non-melanized ones, indicating the enhancement of the electron transfer properties of melanin. The authors concluded that melanin played a major role in protecting the organism against ionizing radiation and these radioprotective properties arise due to its chemical composition, free radical quenching and spherical spatial arrangement. An abundance of highly melanized fungal spores in early Cretaceous period deposits has been uncovered, where other plant and animal species have died out. These types of fungi can be found in high-altitude terrains, Arctic and Antarctic regions, and in the Evolution Canyon in Israel. The south-facing slope of the canyon receives 2–8 times higher solar radiation than those on the north, and Aspergillus niger found there contains 300% higher levels of melanin than that found in the north facing slope. Several groups have studied these effects on melanized fungal species at the Chernobyl accident site and in nuclear reactor pool water.
The discussion above shows that organisms can develop mechanisms to thrive and to repair damage under the exposure of high radiation dose and, in one case, harvest it for metabolic purposes, but it remains to be shown that the ionizing energy produced by secondary particles is comparable to energies observed in radioactive decay processes known to support radiolysis-based life. The GEANT4 package was used to model the energy deposition rate in subsurface environments. It is a widely used package and is considered a gold standard in modelling particle interactions. The code models all particle interactions as particles traverse through a medium and has been well tested in the planetary science community. As the particles traverse in the subsurface medium, they lose energy by ionizing it. At greater depths, muons become important because of their long range, as discussed earlier. Muons transfer their large kinetic energy to the medium, and also form muonium (μ +e −), which has been found useful for various chemical and biological reactions due to its similarities with the hydrogen atom.
It should be noted that below 15 km, the energy deposition rate is constant due to contribution from neutrinos. Three cases were considered here: a planetary object with no atmosphere so the entire GCR flux deposits energy in the ground; the Earth where most of the radiation is blocked by the atmosphere, and Mars. For each case, the energy deposition in pure ice with 1 g cm −3 density and in standard rock with the density of 2.65 g cm −3 was calculated. The flux of GCRs was taken from Dorman and was incident directly on the planet's surface in the first case and on the planet's atmosphere in subsequent cases. The surface in case 1 is pure ice with 1 g cm −3 density and in case 2 is standard rock with density of 2.65 g cm −3. It must be noted that both pure ice and water give the same results in these simulations. In total, 10 9 particles were used for simulations and the energy deposition profile was obtained in each case.
It must be emphasized that energy deposition calculations depend primarily on the column density of the material through which particles traverse and other factors such as temperature, pressure and atmospheric composition are not important. Figures and show the subsurface energy deposition rates for different cases.
In, the energy deposition rate is approximately 10 7 eV g −1 s −1 close to the surface and drops below 10 5 eV g −1 s −1 in the 10 m depth range. The deposition rate falls sharply in the case of rock due to higher density compared to ice. Because the energy deposition rate is about three orders of magnitude lower in the case of the Earth, it has been displayed separately in. The atmosphere absorbs most of the radiation; however, because of the long range of muons, a small amount of radiation reaches a depth of a few kilometres. Subsurface energy deposition rate as a function of depth in rock of density 2.65 g cm −3 (solid) and water/ice (dots). Vertical axis has energy deposition rate in eV g −1 s −1 and horizontal axis has depth in kilometres. Let us now compare these results with the energy environment of Ca.
The radiolytic model calculations by Lin et al. yielded the net dosage range of alpha particles between 4.25 × 10 5 and 8.52 × 10 5 eV g −1 s −1, beta particles between 6.58 × 10 4 and 4.27 × 10 5 eV g −1 s −1, and for gamma rays between 4.00 × 10 4 and 2.25 × 10 5 eV g −1 s −1. This energy is used to split water molecules into H + and OH − forming H 2O 2.
H 2O 2 in turn reacts with the surrounding medium to form sulfate,. It uses sulfate instead of O 2 and obtains nitrogen from surrounding ammonia ,. As one can see, the energy deposition rate is about an order of magnitude higher close to the surface in case 1 than that available to Ca. Life could evolve a variety of mechanisms to utilize such a large range of energy injected underground.
It could produce molecular hydrogen and oxidants useful for life. Muons can both directly react with molecules present in the medium, and also indirectly through radiolysis products.
A detailed description of all the chemical reactions including the intermediate steps can be found elsewhere. Let us now use these radiation doses to calculate familiar biologically useful processes such as the production of adenosine triphosphate (ATP). The terminal phosphate bond in ATP requires 0.304 eV per molecule. As in the case of Ca. Audaxviator, the total energy produced by radioactive rocks would be potentially divided between radiolysis-powered metabolism, radiation damage and damage repair, only a fraction of the total energy will be utilized for radiolysis.
Based on our simulation results the energy availability shown in approximately ranges between 10 7 and 10 4 eV g −1 s −1, which could potentially produce ATP molecules, and the upper limit of production is approximately 3 × 10 7 ATP molecules g −1 s −1 based on the 0.304 eV per molecule conversion factor and assuming 100% efficiency. It must be mentioned that life, as we know it, requires water, which is a neutral fluid and fits perfectly with temperature variations on Earth. However, other fluids might offer similar functionality in terms of being stable; they may provide transportation of essential nutrients and remain liquid for temperature ranges for that particular planet. Underground water or other fluid sources, in combination with flux of secondary particles can provide a stable self-sustained environment for life to exist. Low energy availability can produce organisms with a very slow metabolism. There is a possibility of an ecosystem thriving on this energy source based on other biochemical bases, and might necessitate alternative approaches to detect life ‘as we don't know it’ , in subsurface environments on Earth and elsewhere.
A laboratory experiment to test this hypothesis could also be performed. It would involve gradually changing the radiation environment of Ca.
Audaxviator, by using different particle radiation beams, keeping the same chemical environment and observing its growth over a period of time. If the organism is able to adapt to gradually changing radiation environment, it can be eventually exposed to GCR secondaries proving an ultimate test for the hypothesis. Galactic cosmic ray-induced synthesis of organics and other biologically useful products Even though Ca. Audaxviator is able to maintain an ecosystem independent of photosynthesis, it uses photosynthetic products. Based on experimental results and theoretical models, some authors have proposed that high-energy particles could produce the amino acid glycine on extraterrestrial ices. In this section, it is proposed that biologically useful products, using a similar mechanism, can be produced in subsurface environments by GCR-induced secondaries. Charged particles directly interact with ice and produce a number of biologically useful secondary products –.
Particle Physics Schools
Hudson & Moore irradiated different mixtures of water and CO (carbon monoxide) with 0.8 MeV protons at temperatures near 16 K in order to simulate interstellar conditions. The results of isotopic substitution and IR spectroscopy showed the formation of several hydrocarbons such as HCOOH, HCO −, H 2CO and CH 3OH.
Earlier experiments of Bernstein et al. Were conducted with a larger temperature range (12–300 K), and in addition to the above-mentioned products, they discovered hexamethylenetetramine (C 6H 12N 4), ethers, alcohols, compounds related to polyoxymethylene, ketones and amides in their samples. Their subsequent experiments showed the formation of aroma-bearing ketones and carbolylic acid functional groups. Other groups have also reported experimental evidence of the formation of amino acid precursors on exposure to high-energy particles ,. Kobayashi et al. , irradiated several ice mixtures composed of methane, CO and ammonia with high-energy protons.
The results of quadrupole mass spectrometry and ion exchange chromatography showed the formation of amino acids, such as glycine and alanine, and some hydrocarbons. Garrod & Herbst conducted charged particle-induced photodissociation calculations to model chemical changes from interstellar radiation field and GCRs and reported the production of complex chemicals such as formic acid, methyl formate and dimethyl ether. One common feature of these studies is that they all consider organic synthesis on the surface, which is true for high-energy photons such as UV, X-rays and low energy protons (approx. However, for higher energy particles such as GCRs whose energies are approximately 10 GeV and beyond, the secondary particles penetrate below the surface. Particles such as electrons, positrons, neutrons and photons produced in interactions have very short ranges and are confined in a relatively small volume. Particles with the highest range are muons as shown in and are the primary source of GCR-induced radiation in such environments. In order to validate this hypothesis, one can irradiate samples with muons produced in accelerator experiments.
Muons can also be approximated with electrons in laboratory experiments to a certain extent because electrons also undergo electromagnetic interactions like muons; however, they lose energy very quickly, which makes this test possible only at low energies. Based on the studies cited above, an additional mechanism supporting subsurface life could be direct organic synthesis induced by GCR-induced secondary particles, especially muons at greater depths.
There is experimental evidence of the formation of amino acid precursors on exposure to high-energy particles ,. This mechanism could be especially important in the case of comets, as cosmic ray-induced ionization is believed to be the main driver of cometary organic chemistry. Organic synthesis occurring at the polar regions of the Moon, Mercury and other silicate bodies has also been proposed. There are studies of GCR-induced synthesis of organic molecules in Titan's atmosphere , production of oxidants on Europa and the possibility of an aerial biosphere on Venus. The production of O 2, H 2O 2 and other oxidants on Europa's surface by charged particles accelerated in the Jovian magnetic field has been estimated in an earlier study.
They proposed that through impact gardening, these biologically useful chemicals could be transported to Europa's oceans. Ionization through 40K decay was also considered. Because GCRs are much more energetic compared with particles considered in the above study, in addition to producing these chemicals on Europa's surface, GCR secondaries can directly produce them in ice below the surface.
Let us now calculate the energy deposited in the ice shell of Europa from GCRs. The average energy deposited from 0 to 1 m depth is approximately 10 15 eV g −1 yr −1. For this 1 m shell for entire Europa, the total energy is approximately 1.6 × 10 32 eV yr −1, which would produce 2.4 × 10 7 mol yr −1 of H 2 and O 2.
This scenario is valid in other cases too where non-photosynthetic chemicals can be produced in subsurface environments using this mechanism. 3. Implications on the origin of life and possibility of finding life beyond Earth It is believed that approximately 3.5–4 Gyr ago, when life originated on the Earth, the Sun was in a highly active phase. In this scenario, the Earth's surface was likely to be bombarded by a high flux of energetic solar particles and super coronal mass ejections. Enhanced flux of solar particles and variability in the GCR flux can also enhance the rate of lightning , and provide energy to the prebiotic soup to synthesize amino acids and other organic compounds forming the building blocks of life. If the solar particles are sufficiently energetic (more than 10 GeV), they can produce secondary particles capable of penetrating underground and in water , providing a small source of energy away from direct exposure to high flux of harmful UV radiation on the surface. Solar particles typically reach energies of hundreds of MeV during violent eruptions and in some cases greater than 10 GeV.
Typical solar proton events (SPEs) produce a fluence of about 10 9 protons cm −2 on Earth. Because the Sun was considerably more active in the past, it is highly likely that such eruptions might have occurred on the Sun more frequently. The higher energy component of these SPEs , just like GCRs, is capable of penetrating underground , and would have increased the flux of secondary particles in subsurface environments. A combination of particle flux along with water and nutrients might provide ideal conditions for life to originate and evolve until conditions on the surface become optimal.
As independent/freely floating or ‘rogue’ planets are not tied to any stellar system, they do not receive a steady stream of photons from a parent star. A mechanism has been proposed which could support life on such planets with a combination of sufficient pressure and radioactive heat. Alternatively, GCRs and radioactive materials can be a steady source of energy on such planets. The mechanisms proposed in this paper can be used to synthesize biologically useful chemicals and to power such ecosystems.
Europa is believed to have an abundance of liquid water below its thick ice shell. GCR-induced particles, although cannot provide energy in the ocean, as discussed earlier, they can provide ingredients and fuel to a potential ecosystem in its ice shell. Shows the energy availability from a number of sources on different planetary objects. Objects with no or negligible atmospheres have higher energy availability, about one order of magnitude higher than that available to Ca. Audaxviator from radioactive rocks. There are no other such organisms found on Earth so far.
One reason could be that due to a substantial atmosphere, most of the radiation is blocked and only a small amount is available in subsurface environments. As seen in, the energy availability on Earth is three orders of magnitude smaller than that found on Mars and about two orders of magnitude smaller than used by Ca.
As in the case of Ca. Audaxviator, where the total energy produced by radioactive rocks is divided between radiolysis-powered metabolism, radiation damage and damage repair, it is possible that a fraction of this energy deposited by GCRs can be utilized for metabolic purposes.
Energy availability from GCR simulations and other sources. GCR results show the maximum energy deposited, which is near the surface and drops with depth. For radioactive rocks, the value is the average obtained from Lin et al. For hydrothermal. There is growing evidence of pockets of near-surface water on Mars.
The presence of indigenous nitrogen in sedimentary and aeolian deposits using the SAM instrument on-board the Curiosity rover was reported recently. Observations of hydrated salts, magnesium perchlorate, magnesium chlorate and sodium perchlorate on the Martian surface, were also recently announced. Radiolysis-powered ecosystems can use these chemicals for metabolic processes. The possibility of methane, N 2 and traces of O 2 being by-products of such an ecosystem cannot be ruled out and could possibly explain the presence of methane , that cannot yet be explained by standard physics and chemistry models ,. 4. Conclusion Studying the biological effects of ionizing radiation is a growing area of research. Much of the effort has been focused on examining its damaging effects on human health in context of radiation oncology, nuclear accidents and astronaut health in outer space.
Several experiments have shown ionizing radiation to synthesize organic compounds on interaction with ice mixtures. The discovery of Ca. Audaxviator thriving 2.8 km below the Earth's surface powered by radiolysis opens up new possibilities of biological interaction with (ionizing) particle radiation.
GCRs produce secondary particles that deposit energy in the subsurface environment. Conceivable mechanisms have been proposed through which the energy of GCR-induced particles can be used to produce biologically useful products such as organics and utilize energy for radiolysis to power a potential subsurface ecosystem. Ionizing radiation causes damage, and just as in the case of Ca. Audaxviator, a part of the energy deposited in subsurface environments can be used for repairing damage and the rest for chemical reactions and potential biological use. GCRs are a steady source of ionizing radiation throughout the Galaxy and beyond.
Their secondary component can deposit energy underground; muons especially can penetrate several kilometres underground ,–,. It has been shown that GCR-induced radiolysis is a steady source of energy for subsurface environments and could potentially be a viable source of energy supporting such an ecosystem. GCR-induced particles can directly interact with the medium with essential nutrients and synthesize basic chemicals vital for life to develop, analogous to the experiments with high-energy protons and ice mixtures ,. The GCR-induced radiolysis mechanisms proposed in the paper open up new possibilities of life in subsurface environments on a number of planetary bodies such as Mars, Moon, Europa, Enceladus, Pluto and especially ones with negligible atmospheres.
Radiolysis-powered life can either thrive independently, or can consume a combination of sources such as heat from chemical and geological processes. GCR-induced radiolysis can produce a number of ion species leading to the production of biologically useful products such as molecular hydrogen. There is a possibility of life on icy objects in the interplanetary medium such as comets, and other bodies in the interstellar environment.
This energy source could support life locked inside icy objects and facilitate efficient transportation conforming to the panspermia hypothesis. Because rogue or independent planets also receive a steady flux of this radiation, there is a possibility of a thriving subsurface ecosystem on such planets. Ground-based laboratory tests are suggested that can be conducted to validate the hypotheses presented here.
Contents. Etymology The term ray is somewhat of a misnomer due to an historical accident, as cosmic rays were at first, and wrongly, thought to be mostly.
In common scientific usage, high-energy particles with intrinsic mass are known as 'cosmic' rays, while, which are quanta of electromagnetic radiation (and so have no intrinsic mass) are known by their common names, such as or, depending on their. Massive cosmic rays compared to photons In current usage, the term cosmic ray almost exclusively refers to, as opposed to.
Massive particles – those that have – gain additional, mass-energy when they are moving, due to. Through this process, some particles acquire tremendously high mass-energies. These are significantly higher than the of even the highest-energy photons detected to date. The energy of the massless photon depends solely on, not speed, as photons always travel at the. At the higher end of the energy spectrum, relativistic kinetic energy is the main source of the mass-energy of cosmic rays. The, the highest-energy cosmic ray detected to date, had an energy of about 000000000♠3 ×10 20, while the highest-energy gamma rays to be observed, are photons with energies of up to 648700000♠10 14 eV. Hence, the highest-energy detected fermionic cosmic ray was around 000000000♠3 ×10 6 times more energetic than the highest-energy detected cosmic photons.
Composition Of primary cosmic rays, which originate outside of Earth's atmosphere, about 99% are the nuclei of well-known atoms (stripped of their electron shells), and about 1% are solitary electrons (similar to ). Of the nuclei, about 90% are simple (i.e., hydrogen nuclei); 9% are, identical to helium nuclei; and 1% are the nuclei of heavier elements, called.
A very small fraction are stable particles of, such as. The precise nature of this remaining fraction is an area of active research. An active search from Earth orbit for anti-alpha particles has failed to detect them. Energy Cosmic rays attract great interest practically, due to the damage they inflict on microelectronics and life outside the protection of an atmosphere and magnetic field, and scientifically, because the energies of the most energetic (UHECRs) have been observed to approach 3 × 10 20 eV, about 40 million times the energy of particles accelerated by the.
One can show that such enormous energies might be achieved by means of the in. At 50 J, the highest-energy ultra-high-energy cosmic rays have energies comparable to the kinetic energy of a 90-kilometre-per-hour (56 mph) baseball. As a result of these discoveries, there has been interest in investigating cosmic rays of even greater energies. Most cosmic rays, however, do not have such extreme energies; the energy distribution of cosmic rays peaks at 0.3 gigaelectronvolts (4.8 ×10 −11 J). History After the discovery of by in 1896, it was generally believed that atmospheric electricity, of the, was caused only by from radioactive elements in the ground or the radioactive gases or isotopes of they produce. Measurements of ionization rates at increasing heights above the ground during the decade from 1900 to 1910 showed a decrease that could be explained as due to absorption of the ionizing radiation by the intervening air.
Discovery In 1909, developed an, a device to measure the rate of ion production inside a hermetically sealed container, and used it to show higher levels of radiation at the top of the than at its base. However, his paper published in was not widely accepted. In 1911, observed simultaneous variations of the rate of ionization over a lake, over the sea, and at a depth of 3 meters from the surface. Pacini concluded from the decrease of radioactivity underwater that a certain part of the ionization must be due to sources other than the radioactivity of the Earth.
Pacini makes a measurement in 1910. In 1912, carried three enhanced-accuracy Wulf electrometers to an altitude of 5300 meters in a flight. He found the ionization rate increased approximately fourfold over the rate at ground level. Hess ruled out the Sun as the radiation's source by making a balloon ascent during a near-total eclipse. With the moon blocking much of the Sun's visible radiation, Hess still measured rising radiation at rising altitudes.
He concluded 'The results of my observation are best explained by the assumption that a radiation of very great penetrating power enters our atmosphere from above.' In 1913–1914, confirmed Victor Hess' earlier results by measuring the increased ionization rate at an altitude of 9 km. Hess lands after his balloon flight in 1912. Identification wrote that: In the late 1920s and early 1930s the technique of self-recording electroscopes carried by balloons into the highest layers of the atmosphere or sunk to great depths under water was brought to an unprecedented degree of perfection by the German physicist and his group.
To these scientists we owe some of the most accurate measurements ever made of cosmic-ray ionization as a function of altitude and depth. Stated in 1931 that 'thanks to the fine experiments of Professor Millikan and the even more far-reaching experiments of Professor Regener, we have now got for the first time, a curve of absorption of these radiations in water which we may safely rely upon'. In the 1920s, the term cosmic rays was coined by who made measurements of ionization due to cosmic rays from deep under water to high altitudes and around the globe. Millikan believed that his measurements proved that the primary cosmic rays were gamma rays; i.e., energetic photons. And he proposed a theory that they were produced in interstellar space as by-products of the fusion of hydrogen atoms into the heavier elements, and that secondary were produced in the atmosphere by of gamma rays. But then, sailing from to the Netherlands in 1927, found evidence, later confirmed in many experiments, of a variation of cosmic ray intensity with latitude, which indicated that the primary cosmic rays are deflected by the geomagnetic field and must therefore be charged particles, not photons. In 1929, and discovered charged cosmic-ray particles that could penetrate 4.1 cm of gold.
Charged particles of such high energy could not possibly be produced by photons from Millikan's proposed interstellar fusion process. In 1930, predicted a difference between the intensities of cosmic rays arriving from the east and the west that depends upon the charge of the primary particles – the so-called 'east-west effect.' Three independent experiments found that the intensity is, in fact, greater from the west, proving that most primaries are positive. During the years from 1930 to 1945, a wide variety of investigations confirmed that the primary cosmic rays are mostly protons, and the secondary radiation produced in the atmosphere is primarily electrons, photons and. In 1948, observations with nuclear emulsions carried by balloons to near the top of the atmosphere showed that approximately 10% of the primaries are helium nuclei and 1% are heavier nuclei of the elements such as carbon, iron, and lead. During a test of his equipment for measuring the east-west effect, Rossi observed that the rate of near-simultaneous discharges of two widely separated was larger than the expected accidental rate.
In his report on the experiment, Rossi wrote '. it seems that once in a while the recording equipment is struck by very extensive showers of particles, which causes coincidences between the counters, even placed at large distances from one another.' In 1937, unaware of Rossi's earlier report, detected the same phenomenon and investigated it in some detail. He concluded that high-energy primary cosmic-ray particles interact with air nuclei high in the atmosphere, initiating a cascade of secondary interactions that ultimately yield a shower of electrons, and photons that reach ground level. Soviet physicist Sergey Vernov was the first to use to perform cosmic ray readings with an instrument carried to high altitude by a balloon. On 1 April 1935, he took measurements at heights up to 13.6 kilometers using a pair of in an anti-coincidence circuit to avoid counting secondary ray showers.
Derived an expression for the probability of scattering positrons by electrons, a process now known as. His classic paper, jointly with, published in 1937 described how primary cosmic rays from space interact with the upper atmosphere to produce particles observed at the ground level. Bhabha and Heitler explained the cosmic ray shower formation by the cascade production of gamma rays and positive and negative electron pairs. Energy distribution Measurements of the energy and arrival directions of the ultra-high energy primary cosmic rays by the techniques of density sampling and fast timing of extensive air showers were first carried out in 1954 by members of the Rossi Cosmic Ray Group at the. The experiment employed eleven arranged within a circle 460 meters in diameter on the grounds of the Agassiz Station of the. From that work, and from many other experiments carried out all over the world, the energy spectrum of the primary cosmic rays is now known to extend beyond 10 20 eV.
A huge air shower experiment called the is currently operated at a site on the of Argentina by an international consortium of physicists, led by, winner of the 1980 from the, and of the. Their aim is to explore the properties and arrival directions of the very highest-energy primary cosmic rays. The results are expected to have important implications for particle physics and cosmology, due to a theoretical to the energies of cosmic rays from long distances (about 160 million light years) which occurs above 10 20 eV because of interactions with the remnant photons from the origin of the universe. High-energy gamma rays (50 MeV photons) were finally discovered in the primary cosmic radiation by an MIT experiment carried on the OSO-3 satellite in 1967. Components of both galactic and extra-galactic origins were separately identified at intensities much less than 1% of the primary charged particles. Since then, numerous satellite gamma-ray observatories have mapped the gamma-ray sky. The most recent is the Fermi Observatory, which has produced a map showing a narrow band of gamma ray intensity produced in discrete and diffuse sources in our galaxy, and numerous point-like extra-galactic sources distributed over the celestial sphere.
Sources of cosmic rays Early speculation on the sources of cosmic rays included a 1934 proposal by Baade and suggesting cosmic rays originated from supernovae. A 1948 proposal by suggested that magnetic variable stars could be a source of cosmic rays. Subsequently, in 1951, Y. Sekido et al. Identified the as a source of cosmic rays. Since then, a wide variety of potential sources for cosmic rays began to surface, including, and.
Quantum Physics
Sources of ionizing radiation in interplanetary space. Later experiments have helped to identify the sources of cosmic rays with greater certainty. In 2009, a paper presented at the (ICRC) by scientists at the showed (UHECRs) originating from a location in the sky very close to the, although the authors specifically stated that further investigation would be required to confirm Cen A as a source of cosmic rays. However, no correlation was found between the incidence of gamma-ray bursts and cosmic rays, causing the authors to set upper limits as low as 3.4 × 10 −6 cm −2 on the flux of 1 GeV – 1 TeV cosmic rays from gamma-ray bursts. In 2009, supernovae were said to have been 'pinned down' as a source of cosmic rays, a discovery made by a group using data from the. This analysis, however, was disputed in 2011 with data from, which revealed that 'spectral shapes of hydrogen and helium nuclei are different and cannot be described well by a single power law', suggesting a more complex process of cosmic ray formation.
In February 2013, though, research analyzing data from revealed through an observation of neutral pion decay that supernovae were indeed a source of cosmic rays, with each explosion producing roughly 3 × 10 42 – 3 × 10 43 of cosmic rays. However, supernovae do not produce all cosmic rays, and the proportion of cosmic rays that they do produce is a question which cannot be answered without further study. In 2017, a research paper using data from the International Space Station identified a possible source as dark matter being 'a self-annihilating WIMP'. Types Cosmic rays can be divided into two types, galactic cosmic rays ( GCR), high energy particles originating outside the solar system, and, high energy particles (predominantly protons) emitted by the sun, primarily in. However, the term 'cosmic ray' is often used to refer to only the GCR flux.
Despite the nomenclature galactic, GCRs may originate within or outside the galaxy (as discussed in the source section above). Primary cosmic particle collides with a molecule of atmosphere. Cosmic rays originate as primary cosmic rays, which are those originally produced in various astrophysical processes. Primary cosmic rays are composed primarily of protons and (99%), with a small amount of heavier nuclei (1%) and an extremely minute proportion of and. Secondary cosmic rays, caused by a decay of primary cosmic rays as they impact an atmosphere, include, and. Of these four, the latter three were first detected in cosmic rays.
Primary cosmic rays Primary cosmic rays primarily originate from outside the and sometimes even the. When they interact with Earth's atmosphere, they are converted to secondary particles.
The mass ratio of helium to hydrogen nuclei, 28%, is similar to the primordial ratio of these elements, 24%. The remaining fraction is made up of the other heavier nuclei that are typical nucleosynthesis end products, primarily, and. These nuclei appear in cosmic rays in much greater abundance (1%) than in the solar atmosphere, where they are only about 10 −11 as abundant as. Cosmic rays made up of charged nuclei heavier than helium are called.
Due to the high charge and heavy nature of HZE ions, their contribution to an astronaut's in space is significant even though they are relatively scarce. This abundance difference is a result of the way secondary cosmic rays are formed.
Carbon and oxygen nuclei collide with interstellar matter to form, and in a process termed. Spallation is also responsible for the abundances of, and in cosmic rays produced by collisions of iron and nickel nuclei with. Primary cosmic ray antimatter.
See also: Satellite experiments have found evidence of and a few antiprotons in primary cosmic rays, amounting to less than 1% of the particles in primary cosmic rays. These do not appear to be the products of large amounts of antimatter from the Big Bang, or indeed complex antimatter in the universe. Rather, they appear to consist of only these two elementary particles, newly made in energetic processes. Preliminary results from the presently operating ( AMS-02) on board the show that positrons in the cosmic rays arrive with no directionality, and with energies that range from 10 to 250 GeV. In September, 2014, new results with almost twice as much data were presented in a talk at CERN and published in Physical Review Letters.
A new measurement of positron fraction up to 500 GeV was reported, showing that positron fraction peaks at a maximum of about 16% of total electron+positron events, around an energy of 275±32 GeV. At higher energies, up to 500 GeV, the ratio of positrons to electrons begins to fall again.
The absolute flux of positrons also begins to fall before 500 GeV, but peaks at energies far higher than electron energies, which peak about 10 GeV. These results on interpretation have been suggested to be due to positron production in annihilation events of massive particles. Cosmic ray antiprotons also have a much higher average energy than their normal-matter counterparts (protons). They arrive at Earth with a characteristic energy maximum of 2 GeV, indicating their production in a fundamentally different process from cosmic ray protons, which on average have only one-sixth of the energy. There is no evidence of complex antimatter atomic nuclei, such as nuclei (i.e., anti-alpha particles), in cosmic rays. These are actively being searched for.
A prototype of the AMS-02 designated AMS-01, was flown into space aboard the on in June 1998. By not detecting any at all, the AMS-01 established an upper limit of 1.1 × 10 −6 for the antihelium to helium ratio.
The Moon as seen by the, in gamma rays with energies greater than 20 MeV. These are produced by cosmic ray bombardment on its surface. Secondary cosmic rays When cosmic rays enter the they collide with and, mainly oxygen and nitrogen. The interaction produces a cascade of lighter particles, a so-called secondary radiation that rains down, including, protons, and.
All of the produced particles stay within about one degree of the primary particle's path. Typical particles produced in such collisions are and charged such as positive or negative and. Some of these subsequently decay into, which are able to reach the surface of the Earth, and even penetrate for some distance into shallow mines. The muons can be easily detected by many types of particle detectors, such as, or detectors. The observation of a secondary shower of particles in multiple detectors at the same time is an indication that all of the particles came from that event.
Cosmic rays impacting other planetary bodies in the Solar System are detected indirectly by observing high energy emissions by gamma-ray telescope. These are distinguished from radioactive decay processes by their higher energies above about 10 MeV.
Cosmic-ray flux. An overview of the space environment shows the relationship between the solar activity and galactic cosmic rays. The of incoming cosmic rays at the upper atmosphere is dependent on the, the, and the energy of the cosmic rays. At distances of 94 from the Sun, the solar wind undergoes a transition, called the, from supersonic to subsonic speeds.
The region between the termination shock and the acts as a barrier to cosmic rays, decreasing the flux at lower energies (≤ 1 GeV) by about 90%. However, the strength of the solar wind is not constant, and hence it has been observed that cosmic ray flux is correlated with solar activity.
In addition, the Earth's magnetic field acts to deflect cosmic rays from its surface, giving rise to the observation that the flux is apparently dependent on, and. The combined effects of all of the factors mentioned contribute to the flux of cosmic rays at Earth's surface. The following table of participial frequencies reach the planet and are inferred from lower energy radiation reaching the ground Particle energy (eV) Particle rate (m −2s −1) 000000000♠1 ×10 9 (GeV) 000000000♠1 ×10 4 000000000♠1 ×10 12 (TeV) 1 000000000♠1 ×10 16 (10 PeV) 000000000♠1 ×10 −7 (a few times a year) 000000000♠1 ×10 20 (100 EeV) 000000000♠1 ×10 −15 (once a century) In the past, it was believed that the cosmic ray flux remained fairly constant over time. However, recent research suggests 1.5 to 2-fold millennium-timescale changes in the cosmic ray flux in the past forty thousand years.
The magnitude of the energy of cosmic ray flux in interstellar space is very comparable to that of other deep space energies: cosmic ray energy density averages about one electron-volt per cubic centimeter of interstellar space, or 1 eV/cm 3, which is comparable to the energy density of visible starlight at 0.3 eV/cm 3, the energy density (assumed 3 microgauss) which is 0.25 eV/cm 3, or the (CMB) radiation energy density at 0.25 eV/cm 3. Detection methods. The array of air Cherenkov telescopes.
There are several ground-based methods of detecting cosmic rays currently in use. The first detection method is called the air Cherenkov telescope, designed to detect low-energy (.
Comparison of radiation doses, including the amount detected on the trip from Earth to Mars by the on the (2011 – 2013). Extensive air shower (EAS) arrays, a second detection method, measure the charged particles which pass through them.
EAS arrays measure much higher-energy cosmic rays than air Cherenkov telescopes, and can observe a broad area of the sky and can be active about 90% of the time. However, they are less able to segregate background effects from cosmic rays than can air Cherenkov telescopes. EAS arrays employ plastic in order to detect particles. Another method was developed by Robert Fleischer, and for use in high-altitude balloons. In this method, sheets of clear plastic, like 0.25 polycarbonate, are stacked together and exposed directly to cosmic rays in space or high altitude.
The nuclear charge causes chemical bond breaking or in the plastic. At the top of the plastic stack the ionization is less, due to the high cosmic ray speed. As the cosmic ray speed decreases due to deceleration in the stack, the ionization increases along the path. The resulting plastic sheets are 'etched' or slowly dissolved in warm caustic solution, that removes the surface material at a slow, known rate. The caustic sodium hydroxide dissolves the plastic at a faster rate along the path of the ionized plastic. The net result is a conical etch pit in the plastic. The etch pits are measured under a high-power microscope (typically 1600× oil-immersion), and the etch rate is plotted as a function of the depth in the stacked plastic.
This technique yields a unique curve for each atomic nucleus from 1 to 92, allowing identification of both the charge and energy of the cosmic ray that traverses the plastic stack. The more extensive the ionization along the path, the higher the charge.
In addition to its uses for cosmic-ray detection, the technique is also used to detect nuclei created as products of. A fourth method involves the use of to detect the secondary muons created when a pion decays. Cloud chambers in particular can be built from widely available materials and can be constructed even in a high-school laboratory.
A fifth method, involving, can be used to detect cosmic ray particles. Another method detects the light from nitrogen fluorescence caused by the excitation of nitrogen in the atmosphere by the shower of particles moving through the atmosphere. This method allows for accurate detection of the direction from which the cosmic ray came. Finally, the devices in pervasive cameras have been proposed as a practical distributed network to detect air showers from ultra-high energy cosmic rays (UHECRs) which is at least comparable with that of conventional cosmic ray detectors.
The, which is currently in beta and accepting applications, is CRAYFIS (Cosmic RAYs Found In Smartphones). Effects Changes in atmospheric chemistry Cosmic rays ionize the nitrogen and oxygen molecules in the atmosphere, which leads to a number of chemical reactions. One of the reactions results in ozone depletion. Cosmic rays are also responsible for the continuous production of a number of in the Earth's atmosphere, such as, via the reaction: n + 14N → p + 14C Cosmic rays kept the level of in the atmosphere roughly constant (70 tons) for at least the past 100,000 yearsuntil the beginning of above-ground nuclear weapons testing in the early 1950s. This is an important fact used in used in. Reaction products of primary cosmic rays, radioisotope half-lifetime, and production reaction. Main article: Galactic cosmic rays are one of the most important barriers standing in the way of plans for interplanetary travel by crewed spacecraft.
Cosmic rays also pose a threat to electronics placed aboard outgoing probes. In 2010, a malfunction aboard the space probe was credited to a single flipped bit, probably caused by a cosmic ray.
Strategies such as physical or magnetic shielding for spacecraft have been considered in order to minimize the damage to electronics and human beings caused by cosmic rays. Flying 12 kilometres (39,000 ft) high, passengers and crews of are exposed to at least 10 times the cosmic ray dose that people at receive.
Cosmic Rays Particle Physics Gaisser Pdf Files Download
Aircraft flying near the are at particular risk. Role in lightning Cosmic rays have been implicated in the triggering of electrical breakdown in. It has been proposed that essentially all lightning is triggered through a relativistic process, ', seeded by cosmic ray secondaries. Subsequent development of the lightning discharge then occurs through 'conventional breakdown' mechanisms.
Postulated role in climate change A role of cosmic rays directly or via solar-induced modulations in climate change was suggested by in 1959 and by in 1975. It has been postulated that cosmic rays may have been responsible for major climatic change and mass-extinction in the past.
According to Adrian Mellott and Mikhail Medvedev, 62 million year cycles in biological marine populations correlate with the motion of the earth relative to the galactic plane and increases in exposure to cosmic rays. The researchers suggest that this and bombardments deriving from local could have affected and, and might be linked to decisive alterations in the Earth's climate, and to the of the. Dutch physicist has argued that because modulates the cosmic ray flux on Earth, they would consequently affect the rate of cloud formation and hence be an indirect cause of. Svensmark is one of several scientists. Other scientists have vigorously criticized Svensmark for sloppy and inconsistent work: one example is adjustment of cloud data that understates error in lower cloud data, but not in high cloud data; another example is 'incorrect handling of the physical data' resulting in graphs that do not show the correlations they claim to show.
Research and experiments.