What are Cosmic Rays?

• Cosmic rays are streams of energetic particles and clusters of particles coming from outer space and the sun. They include protons and alpha particles (nuclei of helium atoms). 
• Only low-intensity cosmic rays reach the earth’s surface. Their energy is mostly lost in the atmosphere itself, as they smash into atoms of the atmospheric gases and produce a shower of other particles. Otherwise life wouldn’t have been possible on the earth. 

Types of Cosmic Rays

• Cosmic rays can be divided into two types: those originating from beyond our solar system, called galactic cosmic rays (GCR), and high-energy particles emitted by the sun, called solar cosmic rays, that are mainly protons.
• Solar cosmic rays originate primarily in solar flares.
• GCRs are slowly changing streams of high-energy particles that constantly strike the earth. They are thought to originate outside the solar system in events such as supernovae. (A supernova is an explosion that occurs when a massive star nears the end of its life after running out of matter that it can fuse.)
• Although some 89% of GCRs is hydrogen, the remainder includes the nuclei of all elements, down to and including trace amounts of uranium. These nuclei are also fully ionized, meaning all of their electrons have been stripped away. As a result, these particles interact with and are affected by magnetic fields. This is why the sun’s strong magnetic fields alter the energy levels of GCRs reaching the earth.
• When cosmic ray particles reach the earth’s atmosphere, they ionize air molecules that are at least about 3 km above the surface. Beyond that, they will have lost most of their energy.

About Amaterasu

• Amaterasu cosmic ray had an energy of 240 exa-electron-volt (EeV). The electron-volt (eV) is a unit of energy, like joules, used to measure the energy of subatomic particles. The energy of 1 eV is approximately 1.6 × 10-19 joules.
• One joule is the energy required to light a one-watt bulb for one second. The light-particles in sunlight have an energy of about 1.6-3.1 eV, for example.
• When one deuterium nucleus and one tritium nucleus undergo fusion, they release one helium atom, one neutron, and 17.6 million eV of energy. The mass-energy of a single Higgs boson particle, which is considered ‘heavy’, is 125.1 billion eV.
• Cosmic rays typically range in energy from about one billion eV to about 100 billion billion eV. The Amaterasu cosmic ray had an energy of 240 EeV – or 240 billion billion eV. This is extremely high.