The twilight hours often showcase extraordinary atmospheric displays, including the fleeting green flash, the dance of auroras, and the high-altitude glow of noctilucent clouds. These phenomena offer captivating insights into the dynamic interplay between the sun and Earth's atmosphere.
The green flash is a brief optical illusion caused by the Earth's atmosphere refracting sunlight, separating it into colors. Clear air and an unobstructed horizon are necessary for this phenomenon, which typically lasts only a second or two.
Noctilucent clouds (NLCs), composed of ice crystals, appear as luminous, fibrous structures at altitudes of approximately 81 to 85 kilometers. They are visible when the sun, though below the horizon for ground observers, illuminates these exceptionally high clouds, typically occurring in summer for mid to high latitudes. Recent studies suggest that increased methane emissions may contribute to the growing frequency of NLCs by providing more water vapor for ice crystal formation.
Auroras, or the Northern and Southern Lights, are caused by charged particles from the sun interacting with Earth's magnetic field. These particles are directed towards the poles, where they collide with oxygen and nitrogen atoms in the upper atmosphere, causing them to emit light. The intensity and visibility of auroras are closely tied to solar activity.
In June 2025, a rare instance of noctilucent clouds and auroras was documented in Germany. On June 1, 2025, an increase in aurora sightings in Germany was noted following a significant ejection of charged particles from the sun, as reported by Carolin Liefke from the House of Astronomy in Heidelberg, which heightened the chances for aurora sightings even in middle latitudes.
These celestial events serve as a testament to the energetic dialogue between the sun and our planet, offering a glimpse into the intricate workings of our atmosphere and the profound influence of solar activity.