Theory Cosmic Rays

In 1912, Austrian physicist Victor Hess discovered that charged particles, now called cosmic rays, continually enter Earth's atmosphere from every direction, which means space is filled with them. Cosmic rays are high-speed atomic nuclei with a wide range of energy as the most powerful race at almost the speed of light. Earth's atmosphere and magnetosphere shield us from less-energetic cosmic rays, which are the most common. The most common cosmic ray particles are protons or hydrogen nuclei, making up roughly 90 percent, followed by helium nuclei (8 percent) and electrons (1 percent). The remainder contains the nuclei of other elements, with dwindling numbers of heavy nuclei as their mass rises. The most massive stars, on a other hand, forge elements up to iron in their cores and then explode as supernovas, dispersing the material into space. The explosions also create conditions that result in a brief, intense flood of subatomic particles called neutrons. Many of these neutrons can 'stick' to iron nuclei. Some of them subsequently decay into protons, producing new elements heavier than iron.Supernova blast waves provide the boost that turns these particles into high-energy cosmic rays. As a shock wave expands into space, it entraps and accelerates particles until they reach energies so extreme they can no longer be contained. Roughly 20 percent of cosmic rays were thought to arise from massive stars and supernova debris, while 80 percent came from interstellar dust and gas with chemical quantities similar to what's found in the solar system. Astronomers think that neutron stars merger are so thick with neutrons that they could be responsible for most of the very neutron-rich cosmic rays heavier than nickel. When a cosmic ray strikes the nucleus of a molecule of atmospheric gas in the Earth's atmosphere, both explode in a shower of subatomic shrapnel that triggers a cascade of particle collisions. All cosmic rays are direct samples of matter from interstellar space. Cosmic rays produce gamma rays when they interact with interstellar gas clouds and starlight like in a galaxy as cosmic rays are usually thought to be related to star formation. As particles are electrically charged, they interact with galactic magnetic fields. Cosmic rays are produced by a variety of violent events in space. Most cosmic rays originating within our solar system have relatively low energy and come from explosive events on the Sun, like flares and coronal mass ejections. The highest-energy cosmic rays are extremely rare and are thought to be powered by massive black holes gorging on matter at the center of other galaxies. Galactic cosmic rays come from our Milky Way Galaxy. They are thought to be generated by shock waves from exploding stars called supernovae. Most of the cosmic rays that we detect at Earth originated relatively recently in nearby clusters of massive stars. Cosmic rays are extraordinarily powerful, with energies up to 100 million times greater than particles from manmade colliders. Cosmic rays' particles feature their own antiparticles. When cosmic rays get into collisions, they can produce secondary cosmic rays, which are made up of different ingredients. At the difference of both particles which have no charge in the Universe, the light protons and neutrinos, cosmic rays are charged particles and as such they are absorbed by the Earth's atmosphere. Astronomers think that the most energetic cosmic rays are yielded inside the exotic places of our Milky Way Galaxy, like, for example, supernovae. The makeup of cosmic rays suggest that most of them come from the concentrations of massive stars in certain areas, galactic superbubbles, which are regions where many supernovae explode within a few million years (as in 1949, physicist Enrico Fermi, suggested the highest-energy cosmic rays were accelerated in the magnetic fields of interstellar gas clouds). Rare elements heavier than iron are found among the flux of high-energy cosmic rays. At the difference of the gamma-rays which are reaching us in straight line, from the place they were emitted from, cosmic rays have a complicated journey through our Galaxy! They can ricochet upon the atom in the galactic medium they are hitting or be recaptured and redirected through magnetic fields. The magnetic fields in the expanding shock wave of a supernova remnant is just about the best location for this process to work. All that, thus, is turning into very random the course of cosmic rays and into very hard too to determine their accurate origin. Most of the energetic cosmic rays which are reaching to the Earth might, in fact, be coming from sources close to use, like from pulsars which could not be observed in visible light. Cosmic rays too might originate from the annihilation of hypothetical particles forming 'dark matter', that large part of the Universe the nature of which is still unknown. High-energy cosmic rays, generally, might well be generated by shocks similar to the bow shock of the Earth's magnetosphere, which are created wherever a fast-flowing medium hits an obstacle or another flow. As they are thus found around exploding stars, young stars, black holes and whole galaxies, they might vital to kick-starting the acceleration process of cosmic rays through heating, which would then be guided through large magnetic fields across the Universe at almost the speed of light. Particles with sufficient energy, penetrate both Earth’s magnetosphere and atmosphere and collide with molecules of nitrogen and oxygen as the particles decay into different particles through processes known as 'nucleonic and electromagnetic cascades.' The density of the atmosphere causes the decay to happen at a height mostly of 60,000 feet, yielding a concentrated layer of radiation particles known as the 'Pfotzer maximum.' Cosmic rays, generally, abruptly decline at energies higher than 1,000 trillion electron volts

Cosmic ray acceleration generally could be similar to the SLAMS ('short large amplitude magnetic structures')-originating ion beams seen at the fore of the Earth's magnetosphere, a phenomenon by which the magnetosphere acts like a mirror and reflects the particles of the solar wind. Some kind of such process could also act in terms of cosmic rays, causing particles to bounce back and forth and gain more speed and energy as the mirrors move closer together

Two varieties of cosmic rays are extent. The Galactic Cosmic Rays (GCR), which are electrically charged electrons and atom nuclei reaching our solar system at a speed close to that of speed. 'Pickup' ions are believed to be created when neutral atoms from the Milky Way Galaxy collide with solar ultraviolet light or the solar wind to make charged particles. A alternate view is that cosmic rays are protons mostly accelerated to relativistic speeds in supernova remnants (SNRs), which are the sources of galactic cosmic rays as, when accelerated protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma rays, or 'pion-decay gamma rays.' The identification of pion-decay gamma rays is difficult because high-energy electrons also produce gamma rays via two processes called 'bremsstrahlung' and 'inverse Compton scattering.' When high-speed material ejected by the supernova is ploughing into the previously ejected stationary matter by the dying star, that yields a shock front. Many very rapidly moving protons in the gas directly behing the shock region could be the seed particles to cosmic rays, which then go on to interact with the shock front material to reach the extremely high energies required and fly off into space as cosmic rays. In other words, charged particle trapped in a SRN's magnetic field moves randomly throughout the field and occasionally crosses through the explosion's leading shock wave with each round trip through the shock ramping up the particle's speed by about 1 percent. After many crossings, the particle obtains enough energy to break free and escape into interstellar space as a newborn cosmic ray! The other kind of cosmic rays are those originating from the Sun. The Sun, when in a period of strong activity, is ejecting at high speeds, through the solar flares, more charged particles. A large part of cosmic rays, generally, are shielded by the magnetic fields which are taken with by the solar wind, before they are reaching the inner solar system as the interplanetary magnetic field and the solar wind pressure are doing too. High-energy, or galactic cosmic rays, which are taking their origin from supernova events may be observed through the gamma-rays they are emitting when running into neigbouring gas clouds. Because cosmic rays are composed of charged particles, like protons and electrons, their direction of motion changes when they encounter magnetic fields throughout the galaxy. So, the origin of individual cosmic rays detected on Earth cannot be determined. Supernova likely are a good candidate for producing the most energetic cosmic rays in our Galaxy. The protons can reach energies that are hundreds of times higher than the highest energy electrons produced in the synchrotrons on Earth, which are 14 million times weaker than the power produced by cosmic rays in space. A single trillion electron volt particle for example is about the same amount of energy produced by a mosquito in motion as the fastest cosmic ray yet observed was a subatomic particle with the force of a baseball. The cosmic gamma radiation, as far as it is concerned, comes from all directions and due to the most energetic events in the Universe
Scientists think that magnetic fields on either side of a supernova remnant shock front can trap particles between them in what amounts to a subatomic pingpong game and trigger a pion production process. A proton traveling close to the speed of light strikes a slower-moving proton. Their interaction creates an unstable particle, or a pion, with only 14 percent of the proton's mass. In 10 millionths of a billionth of a second, the pion decays into a pair of gamma rays

Formation zones of O and B type stars look like they are also good candidates as far as the production of cosmic rays are concerned. Such stars are carving cavities into their original gas and dust cloud and cosmic rays are yielded there from supernovae or from repeated interactions with shockwaves generated by the powerful solar winds of such stars. Cosmic rays then come to be intermingled too into turbulent magnetic fields as they can manage to travel further, down to us, once out of such areas. Shock waves, generally, like electron accelerators might be a dominant source of cosmic rays as bow shocks exists both in supernovae events or when a stellar wind impacts a planetary magnetosphere. Of a specific interest are 'quasi-parallel' shocks, where the bow shock and lines of the magnetic field are aligned, which is the case in supernova remnants