Jakarta, Borneo24.com – Aurora is a natural phenomenon that resembles a glowing beam of light in the ionosphere layer, which is seen at the North or South Pole. It looks like blue, red, yellow, green, and orange colored lights shifting gently and changing shape like a gentle blowing curtain.
Auroras are seen nearly every night near the Arctic and Antarctic Circles, which are about 66.5 degrees north and south of the Equator. Auroras usually occur at about 97-1,000 kilometers (60-620 miles) above the Earth’s surface.
NASA calls it a beautiful light show in the sky. Aurora has a different name at each pole. At the North Pole it is called the aurora borealis or northern lights. At the South Pole it is called the aurora australis or southern lights. The perfect moment to see the aurora is at night. In fact, the aurora phenomenon occurs caused by the Sun.
The Moment of the Aurora
Reporting from National Geographic, the activity that creates aurora starts from the sun. The sun is a ball of superheated gas made up of electrically charged particles called ions. Ions that continue to flow from the surface of the sun is called the solar wind. As the solar wind approaches Earth, it encounters the Earth’s magnetic field.
Without a magnetic field protecting the planet, the solar wind would blow away Earth’s fragile atmosphere, most of the solar wind would be blocked by the magnetosphere, and the ions, forced around the planet, would continue to move further into the solar system.
Although most of the solar wind is blocked by the magnetosphere, some ions are trapped in the ring-shaped retaining region around the planet. This region, in the region of the atmosphere called the ionosphere, is centered around Earth’s geomagnetic poles. The geomagnetic pole marks the oblique axis of the earth’s magnetic field, lies about 1,300 kilometers (800 miles) from the geographic pole, but moves slowly.
In the ionosphere, solar wind ions collide with oxygen and nitrogen atoms from Earth’s atmosphere. The energy released during these collisions causes colorful halos around the poles, called auroras. Or when a solar storm approaches Earth, some of the energy and tiny particles can move down the magnetic field lines at the north and south poles into Earth’s atmosphere.
Then, the particles interact with gases in the Earth’s atmosphere to produce a beautiful glow in the sky. Auroras are most active when the solar wind is strongest. The solar wind is usually fairly constant, but the sun’s weather—warming and cooling—can change every day. Solar weather is often measured in sunspots (the coldest part of the sun and appear as dark blobs on its hot surface).
Sun flares and coronal mass ejections are associated with sunspots. Sunspot activity is tracked over an 11-year cycle. Bright, consistent aurorae are most commonly seen during peak sunspot activity. Some increase in solar wind activity occurs during each equinox.
These regular fluctuations are known as magnetic storms. Magnetic storms can cause aurorae to be seen in mid-latitudes around spring and autumn. Not only at the poles, aurora displays have also been seen as far south as the Yucatan Peninsula in Mexico. Magnetic storms and active aurorae can sometimes interfere with communications, causing radio and radar signals to be blocked. Intense magnetic storms can even disable communications satellites.
Aurora Color
The color of the aurora varies, depending on the altitude and the types of atoms involved. If the ions hit oxygen atoms high in the atmosphere, the interaction produces red light. A green-yellow hue occurs when the ions hit the oxygen at lower altitudes.
The reddish and bluish light that often appears at the lower edge of the aurora is produced by ions striking the nitrogen atom. Ions hitting hydrogen and helium atoms can produce blue and purple auroras. But the human eye can rarely detect this part of the electromagnetic spectrum. (***)
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