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When weather conditions are favorable, it is possible to observe a fascinating phenomenon: the parhelion, also known as the “false sun”. This optical phenomenon is part of a larger whole called the solar halo, which consists of several optical phenomena. Indeed, a complete halo can have 6 or 7 components, but it is rare to see them all at the same time. This is how parhelia appear, in the form of two luminous points around the Sun.
These points of light can look like small suns or have rainbow hues. Sometimes they can be so intense that the three points of light, including the Sun in the middle, appear to be the same size, creating a disconcerting vision of three suns aligned. This phenomenon is also known as “sundog” in English. As a general rule, the higher the Sun is in the sky, the farther away the parhelia are from the halo.
Parhelia are caused by the refraction of solar rays in ice crystals. This process requires a Sun low in the sky and an atmosphere laden with ice crystals. This is why this phenomenon is more common in polar regions or in mountains, although it can occur elsewhere.
Ice crystals shaped like an elongated prism, hexagon, or six-pointed star reflect sunlight when they fall due to their weight. These crystals form clouds, such as cirrus or cirrostratus clouds, which allow light rays to pass through. Parhelia are ephemeral, lasting only a few seconds to a few minutes.
In addition to meteorological phenomena, the formation of parhelia can also be observed in aircraft contrails. When the plane passes, it temporarily lowers the temperature at altitude, encouraging the formation of ice crystals. Thus, a parhelion can appear if sunlight hits the contrail crystals at the right angle.
Observing a parhelion, or even a complete halo, can provide insight into the evolution of the weather. Indeed, the appearance of these thin clouds is often followed by meteorological deterioration. Meteorologists sometimes use halos and parhelions as indicators of impending rain, although this is not a hard and fast rule.
In conclusion, the parhelion is a fascinating optical phenomenon resulting from the refraction of solar rays in ice crystals. Its formation is linked to particular weather conditions and it offers a unique visual spectacle that arouses wonder in attentive observers.
For more information on this topic, you can visit the following links:
– Media Congo Article
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