Beth Spangler, age 14, of Springfield, I11., for her question:
WHAT ARE COSMIC RAYS?
Cosmic rays are particles of high energy that originate in outer space. Many of the rays can penetrate deep into the Earth.
Rays from radium, nuclear bombs or X ray machines can barely penetrate two inches of lead. Cosmic rays, on the other hand, have tremendous penetration power.
Cosmic rays can be detected in deep mines, at the surface of the Earth and on high mountain tops. All of these are called secondary cosmic rays. Primary cosmic rays come from outside the Earth's atmosphere.
Secondaries are made up of all the known sub atomic particles, including neutrons, electrons and positrons. High energy X rays, or gamma rays, are also present.
At sea level, about 10 secondaries pass through one square inch of the surface of the Earth every minute. The intensity increases up to several hundred secondaries in one square inch each minute about 10 miles above the Earth.
The primaries are atomic nuclei with energies from a few hundred million to many trillions of electron volts. About 87 percent of the primaries are protons, 12 percent are helium nuclei and the rest are nuclei or heavier elements.
When eruptions on the sun occur most frequently, the cosmic ray intensity is usually less than when the sun is not active. In 1957, for example, there was a great deal of solar activity. Yet in that year, the total cosmic ray intensity was about a third of the total cosmic ray intensity in 1954, a year of little solar activity.
The sun has an 11 year cycle of activity, and so do cosmic rays.
Large increases in cosmic ray intensity sometimes accompany giant explosions, or solar flares, on the sun. The solar flare of Feb. 23, 1956, increased cosmic ray intensity about 50 times the normal at some places. Particles came from the sun a few minutes after the flare was seen. The intensity remained above normal many hours after the flare ceased.
Physicists say that a barrier exists in the solar system beyond the orbit of the Earth. Some cosmic rays pass through this barrier. But it reflects others.
If the barrier did not exist, cosmic ray intensity would return to normal shortly after the flare ceased. The particles would escape directly into the galaxy. The barrier causes them to be scattered back and forth in the inner part of the solar system before they escape.
This same barrier should also affect cosmic rays traveling towards the solar system from the rest of the galaxy. It probably contains magnetic fields that deflect and reflect particles.
Physicists say that material ejected from the sun produces the barrier. The quantity of material ejected depends on the sun's activities.
The barrier is stronger at times of increased solar activity and lets fewer cosmic rays through. Changes in strength of the barrier probably produce the 11 year cycle of intensity and the variations in cut off energy.