Cloud Corona Over Curitiba, Brazil

November 24, 2016


Photographer: Mario Freitas
Summary Author: Mario Freitas

Shown above is a cloud corona as observed over Curitiba, Brazil. The very bright spot at the bottom of the photo corresponds to a small portion of the solar disk, shielded behind the branches of a tipu tree (Tipuana tipu). Floating in our atmosphere, a multitude of similarly sized, spherical, water droplets in a filamented altocumulus cloud exhibit white or metallic-colored hues, depending on their angular positions with the Sun. This optical phenomenon is known as iridescence and results from diffraction; a process that causes the color bands close to the light source (in this case the Sun) to overlap. You can see how the bands suggest the formation of a corona. This is not to be confused with the aura of plasma surrounding the Sun that's visible during the total phase of a solar eclipse. Note how the tipu's pinnated, compound leaves stand out against the background of the deep blue sky. Always use extreme caution when looking at the brighter portion of the sky in the neighborhood of the Sun. Photo taken on November 11, at 12:36 p.m.