Beautiful Dancing Waves!!

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Beautiful Dancing Waves

  Imagine you are under a dark sky and suddenly the colorful waves appear in the sky and turns darkness into the bright beautiful sky filled with different colours of rainbow and their shades. Those beautiful dancing waves are the “Auroras” or Polar Lights. 

  Polar lights (aurora polaris) are a natural phenomenon found in both the northern and southern hemispheres that can be truly awe inspiring. Northern lights are also called by their scientific name aurora borealis, and southern lights are called aurora australis. 

History 

  It wasn’t until 1619 though, that Galileo Galilei coined the term "aurora borealis." Derived from the Greek words "aurora" meaning "sunrise," and "boreas" meaning "wind," the Greeks believed Aurora to be the sister of Helios and Selene. Helios was the sun. Selene was the moon.

  Later on, Henry Cavendish recorded the first scientific observations of the northern lights in 1790. Using triangulation, the French-born English scientist determined the aurora borealis occurred approximately 60 miles above the Earth’s surface. It was British astronomer Richard Carrington, in 1859, who linked the aurora borealis with the sun.

  And even though Norwegian scientist Kristian Birkeland, in the early 1900s, was the first to explain what caused the northern lights, Benjamin Franklin also had a theory on a ship sailing across the Atlantic. He noted a concentration of electrical charges in the North Pole that intensified by snow and moisture caused the lights. 

But WHY do they happen? 

  The activity that creates auroras begins on the sun. The sun is a ball of superhot gases made up of electrically charged particles called ions. The ions, which continuously stream from the sun’s surface, are called the solar wind.

 As solar wind approaches the Earth, it meets the Earth’s magnetic field. Without this magnetic field protecting the planet, the solar wind would blow away Earth’s atmosphere. Most of the solar wind is blocked by the magnetosphere, and the ions, forced around the planet, continue to travel farther into the solar system.

  Although most of the solar wind is blocked by the magnetosphere, some of the ions become briefly trapped in ring-shaped holding areas around the planet. These areas, in a region of the atmosphere called the ionosphere, are centered around the Earth’s geomagnetic poles. The geomagnetic poles mark the tilted axis of the Earth’s magnetic field. They lie about 1,300 kilometers from the geographic poles, but are slowly moving.

  In the ionosphere, the ions of the solar wind collide with atoms of oxygen and nitrogen from the Earth’s atmosphere. The energy released during these collisions causes a colorful glowing halo around the poles an aurora. Most auroras happen about 97-1,000 kilometers above the Earth’s surface.

  The most active auroras happen when the solar wind is the strongest. The solar wind is usually fairly constant, but solar weather the heating and cooling of different parts of the sun can change daily.

  Solar weather is often measured in sunspots. Sunspots are the coldest part of the sun and appear as dark blobs on its white-hot surface. Solar flares and coronal mass ejections are associated with sunspots. Solar flares and coronal mass ejections are sudden, extra bursts of energy in the solar wind. Sunspot activity is tracked over an 11-year cycle. Bright, consistent auroras are most visible during the high sunspot activity.

  Some increased activity in the solar wind happens during every equinox. These regular fluctuations are known as magnetic storms. Magnetic storms can lead to auroras being seen in the midlatitudes during the time around the spring and autumn. 

Magnetic storms and active auroras can sometimes interfere with communications. They can disrupt radio and radar signals. Intense magnetic storms can even disable communication satellites.

 Coloring an Aurora 

  The colors of the aurora vary, depending on altitude and the kind of atoms involved. If ions strike oxygen atoms high in the atmosphere, the interaction produces a red glow. This is an unusual aurora the most familiar display, a green-yellow, occurs as ions strike oxygen at lower altitudes. Reddish and bluish light that often appears in the lower fringes of auroras is produced by ions striking atoms of nitrogen. Ions striking hydrogen and helium atoms can produce blue and purple auroras, although our eyes can rarely detect this part of the electromagnetic spectrum.

  To find out more about the mysterious light displays, scientists have launched satellites specially designed to study auroras. Until 2005, NASA’s IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) satellite used ultraviolet and radio waves to study auroras and how they are formed.

  Colors and patterns are from the types of ions or atoms being energized as they collide with the atmosphere and are affected by lines of magnetic force. Displays may take many forms, including rippling curtains, pulsating globs, traveling pulses, or steady glows. Altitude affects the colors. Blue violet/reds occur below 100 km, with bright green strongest between 100-240 km. Above 240 km ruby reds appear. 

Best Time of Year: 

Best time to see these northern nightlights is September to March. There is no set time for the northern lights, as solar flare activity can even happen before dark. And best time to see these southern nightlights is although most commonly during May to August. 

Sources

• NOAA's three day forecast and 30minute forecast is available, to increase your chances to watch auroras, watch forecasts after 10 p.m.

• There exist few apps predicting the time for specific locations.

Every astrophile’s, dream forever is to once go and watch auroras… what are you thinking of go and add it your bucketlist. Who knows!! The best aurora of all times will appear once you go to see them.

“The best light shows may be during the most unexpected times.”

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