Stable Auroral Red (SAR) Arc

May 8, 2023

Last month, aurora-like colorful curtains of dazzling light were captured in Ladakh, which is much farther from the polar regions, where auroras usually occurr. The lights are actually billions of charged particles moving into space at ultra-high speeds, and when they arrive in the direction of Earth, they cause a disturbance in the Earth’s magnetic field, enabling us to see the aurora lights.

Stable Auroral Red (SAR) Arc

After analyzing the aurora, Hanle sources confirmed that it appears to be a “stable auroral red (SAR) arc.” SAR arc is a band of reddish light seen in the sky. It is a very rare event in Ladakh. Unlike auroras that exhibit a range of colors in dynamic patterns, SAR arcs have a fixed color and remain static. Geomagnetic activity due to a burst of charged particles from the Sun triggers both auroras and SAR arcs, but their formation mechanisms differ slightly.

A Rare Sight

The occurrence of light particles from the Sun colliding with Earth’s magnetic field is a once-in-a-lifetime event, and it is even more rare to capture it on camera. Luckily, the Indian Astronomical Observatory above Mount Saraswati managed to record the happening. These waves were witnessed from Europe, China, and Ladakh in India. The last time such a phenomenon was witnessed was in 2015.

Not an Air Glow

Instruments at the Indian Astronomical Observatory confirmed that the colored light seen was not “air glow,” which is an unrelated phenomenon that is not visible to the naked eye but often appears as a faint region of color in images of the night sky.

The instruments captured a geomagnetic storm that struck Earth’s magnetic field on April 23-24, causing the charged particles from the Sun to collide with atoms and molecules in the Earth’s atmosphere, resulting in the Northern lights. Auroras can be seen in regions close to Earth’s magnetic poles, and a clear sky can enhance the visibility of these lights.

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