Cosmic rays arrive to the Earth surface in all directions, due to the fact that they are charged particles its intensity changes at diferent latitudes affected by the presence of the magnetic field. That field is around the Earth and it is known as the Magnetosphere. The structure of the magnetosphere is partially determined by the Sun that acts as a star with a dipolar magnetic field. The Sun produces an interplanetary plasma known as the "solar wind" that compress the magnetosphere on the day side and expands it in the night side (See Figure 3).

Figura 3 Artistic sight of the behavior of the Magnetosphere and the Solar Wind.

Particles from the cosmic radiation arrive to the Earth's atmosphere and start a phenomenon known as cosmic ray showers, that are originated from the nuclear reactions between cosmic rays and molecules in the atmosphere, during this cascading process electrons, photons, muons, piones, etc are produced. All of them from a single primary particle of the cosmic radiation.(See Figure 4).

In the Geophysics Institute of the National Autonomous University of Mexico cosmic rays with energies that go from 8.2 GeV (10⁹[eV]) are detected with an instrument known as neutron monitor.

Figura 4 Particles produced during the showers.

Cosmic rays cover a wide range of energies that goes from 10⁹ to 3 X 10²⁰[eV] as is shown in the next figure: