CRaTER Science


LET Spectra

Galactic Cosmic Rays

Solar Proton Events

Biological Effects of


Estimate Your Annual
Radiation Exposure

Radiation dose chart
  (interactive & print versions)

Reading Room

Cancer risk from GCR
  (pdf, 2006)
Cell damage detection
  (pdf, 2005)
One-Two Particle Punch
  (website, 2006)
Cosmic Radiation and Bones
  (text, 2005)
Are We Trapped on Earth?
  (website, 2006)
2006 Space Weather Week
  Presentation by H.Spence
  (pdf, 2006)
  describing instrument
  (pdf, 2006)
Radioactive Moon
  (website, 2005)
Proton Inelastic Processes
  (pdf, 2004)
Monte Carlo Simulation
  to Assess True Risk
  (pdf, 2002)
Response of Silicon-based
  LET Spectrometers
  (pdf, 2005)

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Galactic Cosmic Rays

Galactic Cosmic Rays (or GCRs) are high-energy particles that originate outside of our Solar System. These particles include protons, anti-protons, electrons, positrons and positively charged atomic nuclei whose ultimate origin is unknown to us. They are believed to have been created during stellar fusion processes, or created and subsequently accelerated during supernovae explosions. The energy levels in these particles can vary from 10^3 eV to more than 10^20 eV. Exactly how these particles can attain these energy levels is still unknown.

These highly energetic particles shed their orbital electrons, one electrically charged, and thus become easily influenced first by magnetic field lines in the galaxy, then within our own solar system. For this reason, it is difficult to trace the exact path of any particle that we are able to detect near Earth. Most GCRs that we can detect have likely had encounters first with supernovae remnants, then stellar wind from stars, and other influences. These encounters would affect the energy level of the GCRs, altering their final characteristics when we detect them near Earth.

The Earth's upper atmosphere is constantly bombarded with GCRs. On the land surface of the Earth, we are protected by the many layers of the atmosphere and Earth's magnetic shield. Traveling above the Earth's atmosphere and well away from Earth's magnetic field, however, leaves one vulnerable to any damaging effects of GCRs. With an incoming rate of nearly 100 particles per square meter per second, it is important to gather as much information on GCRs as possible so that we may understand their effects.