What are cosmic rays?

ANSWER 1
Cosmic rays are electromagnetic waves of extremely short wavelength. As the word suggests their origin is from outer space or the cosmos. These rays consist of positively charged particles coming from various galaxies outside the solar system and comprise mainly of protons, alpha particles and positive ions of some heavy elements. The sun is a poor source of cosmic rays.
The distant galaxies are the store houses of charged particles. The high electric and magnetic fields present in these galaxies act as natural accelerators of these particles. The high velocities and the charged nature of these particles attribute the wave nature of these particles. Work on the cosmic rays was first stated by Millikan and Anderson during the early part of this century on balloon flights. The intensity of these rays has been found to vary with altitude, latitude and depth under the sea. The primary cosmic rays interact with the molecules of the atmosphere giving rise to secondary particles like electrons positrons (positively charges particles) and mesons. In fact the anti proton was discovered during cosmic ray studies. Luckily, the thick atmosphere around us is a natural blanket protecting us from these rays.
The work of Vikram Sarabhai and Homi Babha on cosmic rays has given us an immense knowledge on the particles that are fundamental constituents of matter and also an insight into the forces that bind them.
ANSWER 2
Cosmic rays are high energy charged particles. They are produced by the sun and the stars. Before entering into the atmosphere, the cosmic rays consist of 89 percent protons, 9 percent helium nuclei and the remaining 3 percent heavy nuclei. These are called as primary cosmic rays. When these rays collide with the nuclei of the air, they produce nuclear fragments.

These nuclear fragments then carry on splitting process on further collisions producing more such fragments. These are called secondary cosmic rays. At sea level about 70 percent of secondary cosmic rays are mesons, 29 percent are electron positron pairs and 1 percent are heavy particles.