The Source of the Aurora
An aurora is a natural light display in the sky caused by collisions between energetic charged particles from the sun and atoms in Earth's upper atmosphere. These solar particles are carried to Earth on the solar wind, a constant stream of plasma flowing from the sun.
Section 2: Earth's Magnetic Shield
Earth is protected by a magnetic field called the magnetosphere, which deflects most of the solar wind. However, the magnetic field is weakest at the North and South Poles, creating funnel-like openings that allow some of the charged particles to enter our atmosphere in these regions.
Section 3: A Practical Example of Light Creation
Imagine a high-speed electron from the solar wind being guided by Earth's magnetic field toward the North Pole. As it enters the upper atmosphere, it strikes an oxygen atom, transferring its energy. The oxygen atom becomes 'excited' and unstable.
Section 4: Why Auroras Have Different Colors
To return to a stable state, the excited atom releases the extra energy as a particle of light, a photon. The color of this light depends on the type of gas atom and the altitude of the collision. Oxygen typically produces the common green and less common red colors, while nitrogen contributes to blue and purplish-red hues.