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Introduction
Cosmic rays are energetic charged particles that originated from outer space. These particles also produce secondary that penetrates the Earth’s atmosphere and surface. These rays are continuously entering Earth’s atmosphere creating a shower of lower secondary energy particles. Most primary cosmic rays are composed of stable subatomic particles that occur normally on Earth, like protons, atomic nuclei, or electrons. Protons or hydrogen nuclei constitute about 89% of cosmic rays, helium nuclei or alpha particles are 10%, and the remaining 1% are the nuclei of heavier elements. There nuclei make 99% of the cosmic rays. These particles are created when stars explode and are ejected into space. When these reach the earth’s surface they become cosmic rays. It is said that every second 100 rays pass through the human body. The most spectacular form of cosmic rays are aurorae. The particles that make aurorae are low energy compared to the cosmic ray standard. The higher the energy, the rarer aurora occur. Aurora Borealis (northern lights) formed when charged particles that are emitted from the sun, during a solar flare, penetrate Earth’s magnetic field and collide with atoms and molecules in our atmosphere. These collisions result in countless little bursts of light, called photons, which make up the aurora. Collisions with oxygen produce red and green auroras, while nitrogen produces the pink and purple colors. This reaction encircles the polar regions of the earth and occurs at an altitude of 40-400 miles (65-650 km) in a zone called the "Auroral Oval." The aurora borealis most commonly occur between 60°-75° latitude, but during great geomagnetic storms the auroral oval expands equatorially and can reach 30° latitude or further.
An auroral display might be observed any night from dusk until dawn as long as it is dark. The best time to view them is between midnight and 2 am. There is an 11-year solar cycle (on average) that controls the tempo of the aurora.
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