Cosmic radiation

©Enric Cruz López. Used with permission.

Cosmic radiation, also known as cosmic rays, refers to high-energy charged particles originating from outer space that penetrate the Earth’s atmosphere. They are composed of primarily protons (about 89%), helium nuclei (about 10%), and a small percentage of heavier elements, electrons, and gamma rays. Here’s a breakdown of cosmic radiation and its relevance:


  1. Primary Cosmic Rays: These come directly from outer space. Their origins include supernovae, active galactic nuclei, and other astrophysical processes.
  2. Secondary Cosmic Rays: When primary cosmic rays interact with the Earth’s atmosphere, they produce a cascade of secondary particles, which include mesons, electrons, neutrons, and photons. This cascade of particles is called an “air shower.”


  1. Solar Cosmic Rays: These are associated with solar activity, particularly solar flares. They are of lower energy compared to galactic cosmic rays but can be intense in number during solar events.
  2. Galactic Cosmic Rays (GCRs): These are high-energy particles originating from outside the solar system, mainly from within our Milky Way galaxy. Their exact sources are still a matter of scientific investigation but are believed to come from supernovae and remnants of exploded stars.


  1. On Earth’s Atmosphere: Cosmic rays play a role in the ionization of the Earth’s atmosphere. This ionization is crucial for the formation of clouds and affects various atmospheric processes.
  2. On Electronics: High-energy particles can interfere with electronic circuits, especially in high-altitude flights and space missions. This is a significant concern for satellites, spacecraft, and aviation.
  3. On Biological Organisms: There’s concern about the potential biological effects of cosmic radiation, especially for astronauts on long-duration space missions. Prolonged exposure to high levels of cosmic radiation can lead to DNA damage, increasing the risk of cancer and other health issues.


  1. Space Missions: In space travel, shielding strategies are being researched to protect astronauts from cosmic radiation. The Earth’s magnetosphere naturally protects those on its surface, but astronauts outside this protective shield are at risk.
  2. Air Travel: There’s a minor increase in radiation exposure for frequent flyers, especially on polar routes. However, for most people, this exposure is still well below the levels that would cause health concerns.

Relevance to Astrophysics and Climate Science:

Cosmic radiation provides clues about processes happening in distant parts of the universe. They are also of interest to climatologists since they play a role in atmospheric ionization, which could influence cloud formation and climate dynamics.

In summary, cosmic radiation is a complex phenomenon originating from outer space that has implications for various scientific fields, including astrophysics, climatology, and space medicine.

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