Auroras are a natural light phenomenon related to charged particles of solar winds that impact the Earth’s atmosphere at high altitude. Auroras are formed by ionization of atmospheric particles when solar winds result in significant disturbances of the magnetosphere. Subsequently, the energy of these particles is lost to the atmosphere, which emits light in different colors and intensities. Auroras may occur in several forms, but are known best for their green and red bands that illuminate the sky. They can be observed at high latitudes in the Arctic, where they are called Aurora Borealis or the Northern Lights, as well as in the Antarctic, where they are called Aurora Australis or Southern Lights.

Information source: Encyclopaedia Brittannica, Wikipedia

Image: Aurora Borealis as seen from Bear Lake, Alaska, USA. Credit: US Air Force/Joshua Strang.

Tropical Cyclone

Tropical cyclones are massive storm systems that may generate strong winds and heavy rain, as well as high waves, storm surges and even tornadoes. They are characterized by a low-pressure center, called the eye, around which thunderstorms rotate rapidly and spiral outward. Tropical cyclones originate over warm oceans and seas, where the evaporation of large amounts of water creates a vast energy source for storms. Colossal rain clouds form as the hot, moist air rises up in the atmosphere, cools and becomes saturated with water, while the strong rotating winds result from the conservation of angular momentum as the air flows towards the eye of the storm. Together, these processes result in an intense atmospheric circulation system that may continue to grow in size and strength under the right conditions. Tropical cyclones may also be classified as hurricanes or typhoons, depending on their strength and location.

Information source: Encyclopaedia Brittannica, Wikipedia

Image: Cyclone Catarina above the South Atlantic as seen from ISS on March 26, 2004. Credit: NASA.