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Encyclopedia > Cosmic ray
The energy spectrum for cosmic rays

Cosmic rays are energetic particles originating from space that impinge on Earth's atmosphere. Almost 90% of all the incoming cosmic ray particles are protons, about 9% are helium nuclei (alpha particles) and about 1% are electrons. The term "ray" is a misnomer, as cosmic particles arrive individually, not in the form of a ray or beam of particles. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... Air redirects here. ... For other uses, see Proton (disambiguation). ... General Name, symbol, number helium, He, 2 Chemical series noble gases Group, period, block 18, 1, s Appearance colorless Standard atomic weight 4. ... An alpha particle is deflected by a magnetic field Alpha radiation consists of helium-4 nuclei and is readily stopped by a sheet of paper. ... For other uses, see Electron (disambiguation). ...

The variety of particle energies reflects the wide variety of sources. The origins of these particles range from energetic processes on the Sun all the way to as yet unknown events in the farthest reaches of the visible universe. Cosmic rays can have energies of over 1020 eV, far higher than the 1012 to 1013 eV that man-made particle accelerators can produce. (The article on Ultra-high-energy cosmic rays describes the detection of a single particle with an energy of about 50 J, the same as a well-hit tennis ball at 42 m/s [about 94 mph].) There has been interest in investigating cosmic rays of even greater energies.[1] Sol redirects here. ... For other uses, see Universe (disambiguation). ... An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ... Unsolved problems in physics: Why is it that some cosmic rays appear to possess energies that are theoretically too high? In high-energy physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray (subatomic particle) which appears to have extreme kinetic energy, far beyond both its rest mass...

Most cosmic rays originate from extrasolar sources within our own galaxy such as rotating neutron stars, supernovae, and black holes. However, the fact that some cosmic rays have extremely high energies provides evidence that at least some must be of extra-galactic origin (e.g. radio galaxies and quasars); the local galactic magnetic field would not be able to contain particles with such a high energy. The origin of cosmic rays with energies up to 1014 eV can be accounted for in terms of shock-wave acceleration in supernova shells. The origin of cosmic rays with energy greater than 1014 eV remains unknown; however, a large collaborative experiment at the Pierre Auger Observatory is underway to try to answer this question. For the story by Larry Niven, see Neutron Star (story). ... Remnant of Keplers Supernova, SN 1604. ... This article is about the astronomical body. ... An active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas. ... This view, taken with infrared light, is a false-color image of a quasar-starburst tandem with the most luminous starburst ever seen in such a combination. ... Observatory SD Tank of the Pierre Auger Observatory in MalargÃ¼e, Mendoza Province near the Andes range Back view of a tank Pierre Auger Observatory is an international cosmic ray observatory designed to detect ultra high energy cosmic rays -- Oh-My-God particles. ...

Observations have shown that cosmic rays with an energy above 10 GeV (10 x 109 eV) approach the Earth’s surface isotropically (equally from all directions); it has been hypothesised that this is not due to an even distribution of cosmic ray sources, but instead is due to galactic magnetic fields causing cosmic rays to travel in spiral paths. This limits cosmic ray’s usefulness in positional astronomy as they carry no information of their direction of origin. At energies below 10 GeV there is a directional dependence, due to the interaction of the charged component of the cosmic rays with the Earth's magnetic field. For other uses, see Astronomy (disambiguation). ... The magnetosphere shields the surface of the Earth from the charged particles of the solar wind. ...

### Solar cosmic rays

Solar cosmic rays or solar energetic particles (SEP) are cosmic rays that originate from the Sun. The average composition is similar to that of the Sun itself. There exists no clear and sharp boundary between the phase spaces of the solar wind and SEP plasma particle polulations[2]. Solar Energetic Particles are high-energy particles coming from the Sun which had been first observed in the early 1940s. ... Sol redirects here. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ...

The name solar cosmic ray itself is a misnomer because the term cosmic implies that the rays are from the cosmos and not the solar system, but it has stuck. The misnomer arose because there is continuity in the energy spectra, i.e., the flux of particles as a function of their energy, because the low-energy solar cosmic rays fade more or less smoothly into the galactic ones as one looks at increasingly higher energies.[citation needed] Until the mid-1960s the energy distributions were generally averaged over long time intervals, which also obscured the difference. Later, it was found that the solar cosmic rays vary widely in their intensity and spectrum, increasing in strength after some solar events such as solar flares. Further, an increase in the intensity of solar cosmic rays is followed by a decrease in all other cosmic rays, called the Forbush decrease after their discoverer, the physicist Scott Forbush. These decreases are due to the solar wind with its entrained magnetic field sweeping some of the galactic cosmic rays outwards, away from the Sun and Earth. The overall or average rate of Forbush decreases tends to follow the 11-year sunspot cycle, but individual events are tied to events on the Sun, as explained above. dearcrevavsh abgha sha ahshaf // The Forbush decrease is usually observable by particle detectors on Earth within a few days after the CME, and the decrease takes place over the course of a few hours. ...

There are further differences between cosmic rays of solar and galactic origin, mainly in that the galactic cosmic rays show an enhancement of heavy elements such as calcium, iron and gallium, as well as of cosmically rare light elements such as lithium and beryllium. The latter result from the cosmic ray spallation (fragmentation) of heavy nuclei due to collisions in transit from the distant sources to the solar system.[citation needed] For other uses, see Calcium (disambiguation). ... For other uses, see Iron (disambiguation). ... General Name, Symbol, Number gallium, Ga, 31 Chemical series poor metals Group, Period, Block 13, 4, p Appearance silvery white   Standard atomic weight 69. ... This article is about the chemical element named Lithium. ... General Name, symbol, number beryllium, Be, 4 Chemical series alkaline earth metals Group, period, block 2, 2, s Appearance white-gray metallic Standard atomic weight 9. ... Cosmic ray spallation is a form of naturally occuring nuclear fission and nucleosynthesis. ...

### Galactic cosmic rays

See Galactic cosmic ray. Galactic cosmic rays are high-energy charged particles that enter the solar system from the outside. ...

### Extragalactic cosmic rays

See Extragalactic cosmic ray. The energy spectrum for cosmic rays Extragalactic cosmic rays are very-high-energy particles that flow into our solar system from beyond our galaxy. ...

### Ultra-high-energy cosmic rays

See Ultra-high-energy cosmic ray. Unsolved problems in physics: Why is it that some cosmic rays appear to possess energies that are theoretically too high? In high-energy physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray (subatomic particle) which appears to have extreme kinetic energy, far beyond both its rest mass...

### Anomalous cosmic rays

Anomalous cosmic rays (ACRs) are cosmic rays with unexpectedly low energies. They are thought to be created near the edge of our solar system, in the heliosheath, the border region between the heliosphere and the interstellar medium. When electrically neutral atoms are able to enter the heliosheath (being unaffected by its magnetic fields) subsequently become ionized, they are thought to be accelerated into low-energy cosmic rays by the solar wind's termination shock which marks the inner edge of the heliosheath. It is also possible that high energy galactic cosmic rays which hit the shock front of the solar wind near the heliopause might be decelerated, resulting in their transformation into lower-energy anomalous cosmic rays. The locations of Voyagers 1 and 2 as of 2005 The heliosheath is the zone between the termination shock and the heliopause at the outer border of the solar system. ... The heliosphere is a bubble in space produced by the solar wind. ... The interstellar medium (or ISM) is the name astronomers give to the tenuous gas and dust that pervade interstellar space. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... The locations of Voyagers 1 and 2 as of 2005 In space physics, the termination shock is the boundary marking one of the outer limits of the suns influence. ... Galactic cosmic rays are high-energy charged particles that enter the solar system from the outside. ... In a planetary magnetosphere, the bow shock is the boundary at which the solar wind abruptly drops as a result of its approach to the magnetopause. ... The heliopause is the boundary between the heliosphere and the interstellar medium outside the solar system. ...

The Voyager 1 space probe crossed the termination shock on December 16, 2004, according to papers published in the journal Science.[3] Readings showed particle acceleration, but not of the kind that generates ACRs. It is unclear at this stage (September 2005) if this is typical of the termination shock (requiring a major rethink of the origin of ACRs), or a localised feature of that part of the termination shock that Voyager 1 passed through. Voyager 2 is expected to cross the termination shock during or after 2008, which will provide more data. For the album by The Verve, see Voyager 1 (album). ... is the 350th day of the year (351st in leap years) in the Gregorian calendar. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... 2005 : January - February - March - April - May - June - July - August - September - October - November - December- â†’ Deaths in September September 28 : Constance Baker Motley September 25 : M. Scott Peck September 25 : Don Adams September 20 : Simon Wiesenthal September 14 : Robert Wise September 10 : Hermann Bondi September 8 : Donald Horne September 7 : Moussa Arafat... Trajectory Voyager 2 is an unmanned interplanetary spacecraft, launched on August 20, 1977. ... 2008 (MMVIII) will be a leap year starting on Tuesday of the Anno Domini (common) era, in accordance with the Gregorian calendar. ...

## Composition

This abundance difference is a result of the way secondary cosmic rays are formed. When the heavy nuclei components of primary cosmic rays, namely the carbon and oxygen nuclei, collide with interstellar matter, they break up into lighter nuclei (in a process termed cosmic ray spallation), into lithium, beryllium and boron. It is found that the energy spectra of Li, Be and B falls off somewhat steeper than that of carbon or oxygen, indicating that less cosmic ray spallation occurs for the higher energy nuclei presumably due to their escape from the galactic magnetic field. Spallation is also responsible for the abundances of Sc, Ti, V and Mn elements in cosmic rays, which are produced by collisions of Fe and Ni nuclei with interstellar matter; see Environmental radioactivity#Naturals. Cosmic ray spallation is a form of naturally occuring nuclear fission and nucleosynthesis. ... Cosmic ray spallation is a form of naturally occuring nuclear fission and nucleosynthesis. ... The interstellar medium (or ISM) is a term used in astronomy to describe the rarefied gas and dust that exists between the stars (or their immediate circumstellar environment) within a galaxy. ... The environmental radioactivity page is devoted to the subject of radioactive materials in man and his environment. ...

In the past, it was believed that the cosmic ray flux has remained fairly constant over time. Recent research has, however, produced evidence for 1.5 to 2-fold millennium-timescale changes in the cosmic ray flux in the past forty thousand years.[4] flux in science and mathematics. ...

## Modulation

This modulation which describes the change in the interstellar intensities of cosmic rays as they propagate in the heliosphere is highly energy and spatial dependent, and it is described by the Parker's Transport Equation in the heliosphere. At large radial distances, far from the Sun ~ 94 AU, there exists the region where the solar wind undergoes a transition from supersonic to subsonic speeds called the solar wind termination shock. The region between the termination shock and the heliospause (the boundary marking the end of the heliosphere) is called the heliosheath. This region acts as a barrier to cosmic rays and it decreases their intensities at lower energies by about 90% indicating that it is not only the Earth's magnetic field that protect us from cosmic ray bombardment. For more on this topic and how the barrier effects occur the agile reader is referred to Mabedle Donald Ngobeni and Marius Potgieter (2007), and Mabedle Donald Ngobeni (2006). The heliosphere is a bubble in space produced by the solar wind. ... The astronomical unit (AU or au or a. ... The locations of Voyagers 1 and 2 as of 2005 The heliosheath is the zone between the termination shock and the heliopause at the outer border of the solar system. ... Magnetic field lines shown by iron filings Magnetostatics Electrodynamics Electrical Network Tensors in Relativity This box:      In physics, the magnetic field is a field that permeates space and which exerts a magnetic force on moving electric charges and magnetic dipoles. ...

From modelling point of view, there is a challenge in determining the Local Interstellar spectra (LIS) due to large adiabatic energy changes these particles experience owing to the diverging solar wind in the heliosphere. However, significant progress has been made in the field of cosmic ray studies with the development of an improved state-of-the-art 2D numerical model that includes the simulation of the solar wind termination shock, drifts and the heliosheath coupled with fresh descriptions of the diffusion tensor, see Langner et al. (2004). But challenges also exist because the structure of the solar wind and the turbulent magnetic field in the heliosheath is not well understood indicating the heliosheath as the region unknown beyond. With lack of knowledge of the diffusion coefficient perpendicular to the magnetic field our knowledge of the heliosphere and from the modelling point of view is far from complete. There exist promising theories like ab initio approaches, but the drawback is that such theories produce poor compatibility with observations (Minnie, 2006) indicating their failure in describing the mechanisms influencing the cosmic rays in the heliosphere. Scientific modelling is the process of generating abstract or conceptual models. ... In most modern usages of the word spectrum, there is a unifying theme of between extremes at either end. ... The Latin term ab initio means from the beginning and is used in several contexts: when describing literature: told from the beginning as opposed to in medias res (meaning starting in the middle of the story) as a legal term: refers to something being the case from the start or...

## Detection

The Moon's cosmic ray shadow, as seen in secondary muons detected 700m below ground, at the Soudan 2 detector

### Interaction with the Earth's atmosphere

When cosmic ray particles enter the Earth’s atmosphere they collide with molecules, mainly oxygen and nitrogen, to produce a cascade of lighter particles, a so-called air shower. The general idea is shown in the figure which shows a cosmic ray shower produced by a high energy proton of cosmic ray origin striking an atmospheric molecule. Layers of Atmosphere (NOAA) Air redirects here; for other uses, see Air (disambiguation). ... In science, a molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... An Air shower is an extensive (many kilometres wide) cascade of ionized particles and electromagnetic radiation produced in the atmosphere when a primary cosmic ray (i. ...

This image is a simplified picture of an air shower: in reality, the number of particles created in an air shower event can reach in the billions, depending on the energy of the primary particle. All of the produced particles stay within about one degree of the primary particle's path. Typical particles produced in such collisions are charged mesons (e.g. positive and negative pions and kaons); one common collision is: In particle physics, a meson is a strongly interacting boson, that is, it is a hadron with integral spin. ... In particle physics, pion (short for the Greek pi meson = P middle) is the collective name for three subatomic particles discovered in 1947: &#960;0, &#960;+ and &#960;&#8722;. Pions are the lightest mesons. ... In particle physics, a kaon (also called K-meson and denoted K) is any one of a group of four mesons distinguished by the fact that they carry a quantum number called strangeness. ...

$p + mathrm{O}^{16} rightarrow n + pi$

Cosmic rays are also responsible for the continuous production of a number of unstable isotopes in the Earth’s atmosphere, such as carbon-14, via the reaction: A radionuclide is an atom with an unstable nucleus. ... Carbon-14 is the radioactive isotope of carbon discovered February 27, 1940, by Martin Kamen and Sam Ruben. ...

$n + mathrm{N}^{14} rightarrow p + mathrm{C}^{14}$

Cosmic rays have kept the level of carbon-14 in the atmosphere roughly constant (70 tons) for at least the past 100,000 years. This an important fact used in radiocarbon dating which is used in archaeology. Carbon-14 is the radioactive isotope of carbon discovered February 27, 1940, by Martin Kamen and Sam Ruben. ... Radiocarbon dating is a radiometric dating method that uses the naturally occurring isotope carbon-14 (14C) to determine the age of carbonaceous materials up to about 60,000 years. ... For referencing in Wikipedia, see Wikipedia:Citing sources. ...

## Research and experiments

There are a number of cosmic ray research initiatives. These include, but are not limited to:

CHICOS logo The California High School Cosmic Ray Observatory, commonly recognized as CHICOS(California HIgh school Cosmic ray ObServatory), operated by the Kellogg Laboratory sited at the California Institute of Technology, south of Pasadena, California, USA, is one of the the worlds largest ongoing Cosmic Ray observatory program. ... PAMELA logo PAMELA is a bacronym for Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics. ... The Alpha Magnetic Spectrometer is a particle physics experiment to be mounted on the International Space Station designed to search for a various types of unusual matter. ... This article is about the Mexcian musical genre and ensemble. ... Observatory SD Tank of the Pierre Auger Observatory in MalargÃ¼e, Mendoza Province near the Andes range Back view of a tank Pierre Auger Observatory is an international cosmic ray observatory designed to detect ultra high energy cosmic rays -- Oh-My-God particles. ... Spaceship Earth is a world view term usually expressing concern over the use of limited resources available on Earth. ...

## History

In 1934 Bruno Rossi reported an observation of near-simultaneous discharges of two Geiger counters widely separated in a horizontal plane during a test of equipment he was using in a measurement of the so-called east-west effect. 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. Unfortunately, he did not have the time to study this phenomenon more closely." In 1937 Pierre Auger, unaware of Rossi's earlier report, detected the same phenomenon and investigated it in some detail. He concluded that extensive particle showers are generated by high-energy primary cosmic-ray particles that interact with air nuclei high in the atmosphere, initiating a cascade of secondary interactions that ultimately yield a shower of electrons, photons, and muons that reach ground level. Bruno B. Rossi (April 13, 1905 â€“ November 21, 1993) was a leading Italian-American experimental physicist. ... This article or section does not cite any references or sources. ... Pierre Victor Auger (May 14, 1899 â€“ December 25, 1993) was a French physicist, born in Paris. ... An Air shower is an extensive (many kilometres wide) cascade of ionized particles and electromagnetic radiation produced in the atmosphere when a primary cosmic ray (i. ...

Homi Bhabha derived an expression for the probability of scattering positrons by electrons, a process now known as Bhabha scattering. His classic paper, jointly with W. Heitler, 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. In 1938 Bhabha concluded that observations of the properties of such particles would lead to the straightforward experimental verification of Albert Einstein's theory of relativity.

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 Massachusetts Institute of Technology. The experiment employed eleven scintillation detectors arranged within a circle 460 meters in diameter on the grounds of the Agassiz Station of the Harvard College Observatory. 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 1020 eV (past the GZK cutoff, beyond which very few cosmic rays should be observed). A huge air shower experiment called the Auger Project is currently operated at a site on the pampas of Argentina by an international consortium of physicists. 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. â€œMITâ€ redirects here. ... Scintillation detectors make use of the property of certain chemical compounds to emit short light pulses after excitation by the passage of charged particles or by photons (x-rays and gamma-rays). ... Harvard College Observatory, about 1900. ... The Greisen-Zatsepin-Kuzmin limit (GZK limit) is a theoretical upper limit on the energy of cosmic rays from distant sources. ... Observatory SD Tank of the Pierre Auger Observatory in MalargÃ¼e, Mendoza Province near the Andes range Back view of a tank Pierre Auger Observatory is an international cosmic ray observatory designed to detect ultra high energy cosmic rays -- Oh-My-God particles. ... This article is about the lowland plains in South America. ...

Three varieties of neutrino are produced when the unstable particles produced in cosmic ray showers decay. Since neutrinos interact only weakly with matter most of them simply pass through the Earth and exit the other side. They very occasionally interact, however, and these atmospheric neutrinos have been detected by several deep underground experiments. The Super-Kamiokande in Japan provided the first convincing evidence for neutrino oscillation in which one flavour of neutrino changes into another. The evidence was found in a difference in the ratio of electron neutrinos to muon neutrinos depending on the distance they have traveled through the air and earth. For other uses, see Neutrino (disambiguation). ... The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four fundamental interactions of nature. ... Super-Kamiokande, or Super-K for short, is a neutrino observatory in Japan. ... Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvo whereby a neutrino created with a specific lepton flavor (electron, muon or tau) can later be measured to have a different flavor. ... Flavour (or flavor) is a quantum number of elementary particles related to their weak interactions. ...

## Effects

Cosmic rays constitute a fraction of the annual radiation exposure of human beings on earth. For example, the average radiation exposure in Australia is 0.3 mSv due to cosmic rays, out of a total of 2.3 mSv.[1] The sievert (symbol: Sv) is the SI derived unit of dose equivalent. ...

### Significance to space travel

Understanding the effects of cosmic rays on the body will be vital for assessing the risks of space travel. R.A. Mewaldt estimated humans unshielded in interplanetary space receive annually roughly 400 to 900 mSv (compared to 2.4 mSv on Earth) and that a 30 month Mars mission might expose astronauts to 460 mSv (at Solar Maximum) to 1140 mSv (at Solar Minimum).[5] These doses approach the 1 to 4 Sv career limits advised by the National Council on Radiation Protection and Measurements for Low Earth Orbit activities. The Health threat from cosmic rays (termed Space radiation by NASA in this context) is the danger posed by cosmic rays generated by the Sun and other stars to astronauts on interplanetary missions. ... Edward White on a spacewalk during the Gemini 4 mission. ... The National Council on Radiation Protection and Measurements (NCRP) is a U.S. organization which seeks to formulate and widely disseminate information, guidance and recommendations on radiation protection and measurements which represent the consensus of leading scientific thinking. ... A low Earth orbit (LEO) is an orbit in which objects such as satellites are below intermediate circular orbit (ICO) and far below geostationary orbit, but typically around 350 - 1400 km above the Earths surface. ...

High speed cosmic rays can damage DNA, increasing the risk of cancer, cataracts, neurological disorders, and non-cancer mortality risks.[6] The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ... Human eye cross-sectional view, showing position of human lens. ... Neurology is a branch of medicine dealing with disorders of the central and peripheral nervous systems. ...

Due to the potential negative effects of astronaut exposure to cosmic rays, solar activity may play a role in future space travel via the Forbush decrease effect. Coronal mass ejections (CMEs) can temporarily lower the local cosmic ray levels, and radiation from CMEs is easier to shield against than cosmic rays. dearcrevavsh abgha sha ahshaf // The Forbush decrease is usually observable by particle detectors on Earth within a few days after the CME, and the decrease takes place over the course of a few hours. ... A composite image showing two CMEs (at 2 oclock and 8 oclock), with the sun at center. ...

### Role in lightning

Cosmic rays have been implicated in the triggering of electrical breakdown in lightning. It has been proposed (see Gurevich and Zybin, Physics Today, May 2005, "Runaway Breakdown and the Mysteries of Lightning") that essentially all lightning is triggered through a relativistic process, "runaway breakdown", seeded by cosmic ray secondaries. Subsequent development of the lightning discharge then occurs through "conventional breakdown" mechanisms. Not to be confused with lighting. ... This article or section does not cite its references or sources. ...

### Role in climate change

Whether cosmic rays have any role in climate change is disputed. Different groups have made different arguments regarding the role of cosmic ray forcing in climate change.

Shaviv et al. have argued that galactic cosmic ray (GCR) climate signals on geological time scales are attributable to changing positions of the galactic spiral arms of the Milky Way, and that cosmic ray flux variability is the dominant climate driver over these time periods.[7][8] They also argue that GCR flux variability plays an important role in climate variability over shorter time scales, though the relative contribution of anthropogenic factors in relation to GCR flux presently is a matter of continued debate.[9] Because of uncertainty about which GCR energies are the most important drivers of cloud cover variation (if any), and because of the paucity of historical data on cosmic ray flux at various ranges of energies, controversies remain.[10]

Henrik Svensmark et al. have argued that solar variations modulate the cosmic ray signal seen at the earth and that this would affect cloud formation and hence climate. Cosmic rays have been experimentally determined to be able to produce ultra-small aerosol particles,[11] orders of magnitude smaller than cloud condensation nuclei (CCN). Whether this mechanism is relevant to the real atmosphere is unknown; in particular, the steps from this to modulation of cloud formation and thence climate have not been established. The analogy is with the Wilson cloud chamber, however acting on a global scale, where earth's atmosphere acts as the cloud chamber and the cosmic rays catalyze the production of CCN. But unlike a cloud chamber, where the air is carefully purified, the real atmosphere always has many CCN naturally. Various proposals have been made for the mechanism by which cosmic rays might affect clouds, including ion mediated nucleation, and indirect effects on current flow density in the global electric circuit (see Tinsley 2000, and F. Yu 1999). Claims have been made of identification of GCR climate signals in atmospheric parameters such as high latitude precipitation (Todd & Kniveton), and Svensmark's annual cloud cover variations, which were said to be correlated to GCR variation. Henrik Svensmark is an atmospheric scientist at the Danish National Space Center in Copenhagen who studies the effects of cosmic rays on cloud formation. ... Aerosol pollution over Northern India and Bangladesh - NASA Cloud condensation nuclei or CCNs (also known as cloud seeds) are small particles (typically 0. ... Nephology (from the Greek word nephos for cloud) is the study of clouds and cloud formation. ... Discovery of the positron in 1932 by Carl D. Anderson in a cloud chamber . The cloud chamber, also known as the Wilson chamber, is used for detecting particles of ionizing radiation. ... Air redirects here. ... Discovery of the positron in 1932 by Carl D. Anderson in a cloud chamber The cloud chamber, also known as the Wilson chamber, is used for detecting particles of ionizing radiation. ... In chemistry and biology, catalysis (in Greek meaning to annul) is the acceleration of the rate of a chemical reaction by means of a substance, called a catalyst, that is itself unchanged chemically by the overall reaction. ... Aerosol pollution over Northern India and Bangladesh - NASA Cloud condensation nuclei or CCNs (also known as cloud seeds) are small particles (typically 0. ...

That Svensmark's work can be extrapolated to suggest any meaningful connection with global warming is disputed:[12]

At the time we pointed out that while the experiments were potentially of interest, they are a long way from actually demonstrating an influence of cosmic rays on the real world climate, and in no way justify the hyperbole that Svensmark and colleagues put into their press releases and more 'popular' pieces. Even if the evidence for solar forcing were legitimate, any bizarre calculus that takes evidence for solar forcing of climate as evidence against greenhouse gases for current climate change is simply wrong. Whether cosmic rays are correlated with climate or not, they have been regularly measured by the neutron monitor at Climax Station (Colorado) since 1953 and show no long term trend. No trend = no explanation for current changes.[13]

See-also Global warming#Solar variation. Global warming refers to the increase in the average temperature of the Earths near-surface air and oceans in recent decades and its projected continuation. ...

## Cosmic rays and fiction

Because of the metaphysical connotations of the word "cosmic", the very name of these particles enables their misinterpretation by the public, giving them an aura of mysterious powers. Were they merely referred to as "high-speed protons and atomic nuclei" this might not be so.

In fiction, cosmic rays have been used as a catchall, mostly in comics (notably the Marvel Comics group the Fantastic Four), as a source for mutation and therefore the powers gained by being bombarded with them. This article is about the comic book company. ... For other uses, see Fantastic Four (disambiguation). ... For linguistic mutation, see Apophony. ...

## Notes

1. ^ Luis Anchordoqui, Thomas Paul, Stephen Reucroft, John Swain. Ultrahigh Energy Cosmic Rays: The state of the art before the Auger Observatory. (2002) arxiv:hep-ph/0206072
2. ^ Solar wind and solar energetic particles: origins and effects
3. ^ Science, 23 September 2005, Vol 309, Issue 5743
4. ^ Lal, Devendra; A.J.T. Jullb, David Pollardc and Loic Vacher (2005-06-15). "Evidence for large century time-scale changes in solar activity in the past 32 Kyr, based on in-situ cosmogenic 14C in ice at Summit, Greenland". Earth and Planetary Science Letters 234 (3-4): 335-249.
5. ^ The Cosmic Ray Radiation Dose in Interplanetary Space – Present Day and Worst-Case Evaluations R.A. Mewaldt et al, page 103, 29th International Cosmic Ray Conference Pune (2005) 00, 101-104
6. ^ NASA Facts: Understanding Space Radiation
7. ^ sciencebits.com/CosmicRaysClimate
8. ^ sciencebits.com/ice-ages
9. ^ sciencebits.com/CO2orSolar
10. ^ sciencebits.com/ClimateDebate
11. ^ Henrik Svensmark, Jens Olaf Pepke Pedersen, Nigel Marsh, Martin Enghoff and Ulrik Uggerhøj, "Experimental Evidence for the role of Ions in Particle Nucleation under Atmospheric Conditions", Proceedings of the Royal Society A, (Early Online Publishing), 2006.
12. ^ RealClimate: Taking Cosmic Rays for a spin retrieved 22-Feb-2007
13. ^ RealClimate: Nigel Calder in the Times, retrieved 22-Feb-2007

Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 166th day of the year (167th in leap years) in the Gregorian calendar. ... Henrik Svensmark is an atmospheric scientist at the Danish National Space Center in Copenhagen who studies the effects of cosmic rays on cloud formation. ... Cover of Proceedings of the Royal Society is a scientific journal published by the Royal Society of London. ...

## References

• C. D. Anderson and S. H. Neddermeyer, Cloud Chamber Observations of Cosmic Rays at 4300 Meters Elevation and Near Sea-Level, Phys. Rev 50, 263,(1936).
• M. Boezio et al, Measurement of the flux of atmospheric muons with the CAPRICE94 apparatus, Phys. Rev. D 62, 032007, (2000).
• R. Clay and B. Dawson, Cosmic Bullets, Allen & Unwin, 1997. ISBN 1864482044
• T. K. Gaisser, Cosmic Rays and Particle Physics, Cambridge University Press, 1990. ISBN 0521326672
• P. K. F. Grieder, Cosmic Rays at Earth: Researcher’s Reference Manual and Data Book, Elsevier, 2001. ISBN 0444507108
• A. M. Hillas, Cosmic Rays, Pergamon Press, Oxford, 1972 ISBN 0080167241 - A good overview of the history and science of cosmic ray research including reprints of seminal papers by Hess, Anderson, Auger and others.
• J. Kremer et al, Measurement of Ground-Level Muons at Two Geomagnetic Locations, Phys. Rev. Lett. 83, 4241, (1999).
• S. H. Neddermeyer and C. D. Anderson, Note on the Nature of Cosmic-Ray Particles, Phys. Rev. 51, 844, (1937).
• M. D. Ngobeni and M. S. Potgieter, Cosmic ray anisotropies in the outer heliosphere, Advances in Space Research, 2007.
• M. D. Ngobeni, Aspects of the modulation of cosmic rays in the outer heliosphere, M.Sc Dissertation, Northwest University (Potchefstroom campus) South Africa 2006.
• D. Perkins, Particle Astrophysics, Oxford University Press, 2003. - Very interesting and well written book. ISBN 0198509510
• C. E. Rolfs and S. R. William, Cauldrons in the Cosmos, The University of Chicago Press, 1988. ISBN 0226724565
• B. B. Rossi, Cosmic Rays, McGraw-Hill, New York, 1964.
• Martin Walt, Introduction to Geomagnetically Trapped Radiation, 1994. ISBN 0521431433
• J. F. Ziegler, The Background In Detectors Caused By Sea Level Cosmic Rays, Nuclear Instruments and Methods 191, 419, (1981).
• TRACER Long Duration Balloon Project: the largest cosmic ray detector launched on balloons.
• NOAA FTP: Lal, D., et al., 2005. Data on cosmic ray flux derived from C14 concentrations in the GISP2 Greenland ice core.
• BBC news, Cosmic rays find uranium, 2003.
• BBC news, Rays to nab nuclear smugglers, 2005.
• BBC news, Physicists probe ancient pyramid (using cosmic rays), 2004.
• Shielding Space Travelers by Eugene Parker.
• Composition of Solar cosmic rays

The HiRes detector - an atmospheric fluorescence detector: HiRes currently consists of two sites on top of two mountains separated by 13km in western Utah. ... Ice Core sample taken from drill. ...

Results from FactBites:

 cosmic ray: Definition and Much More from Answers.com (4538 words) Cosmic rays were first found to be of extraterrestrial origin by Victor F. Hess (c.1912) when he recorded them with electrometers carried to high altitudes in balloons, an achievement for which he won the Nobel Prize in 1936. Cosmic rays are composed mainly of bare nuclei, roughly 87% protons, 12% alpha particles (helium nuclei) and most of the rest being made up of heavier atomic nuclei with relative abundances comparable to those found in the Sun. Then, during the decade from 1927 to 1937 a wide variety of experimental investigations demonstrated that the primary cosmic rays are mostly positive charged particles, and the secondary radiation observed at ground level is composed primarily of a "soft component" of electrons and photons and a "hard component" of penetrating particles, muons.
 NGDC/WDC STP, Boulder-Cosmic Rays (1037 words) Cosmic rays also have an extreme energy range of incident particles, which have allowed physicists to study aspects of their field that can not be studied in any other way. The portion of the cosmic ray spectrum that reaches the Earth's atmosphere is controlled by the geomagnetic cutoff which varies from a minimum (theoretically zero) at the magnetic poles to a vertical cosmic ray cutoff of about 15 GV (ranging from 13 to 17) in the equatorial regions. The cosmic rays show an inverse relationship to the sunspot cycle because Sun's magnetic field is stronger during sunspot maximum and shields the Earth from cosmic rays.
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