Auroras spotted in India: What makes the phenomenon so rare
On the night of April 22, a geomagnetic storm swept across Earth's magnetic field, sparking brilliant auroras. While auroras happen quite often, in India, the phenomenon is extremely rare. The celestial spectacle occurred at low latitudes and it was the first time that an aurora was snapped on camera in India. It was captured by Indian Astronomical Observatory (IAO).
First, what causes auroras?
Auroras are a result of interactions between high-energy particles streaming from the Sun's atmosphere and the Earth's magnetic field. Depending on the altitude and the type of molecules involved, the color of the auroras changes. The most commonly-seen color of auroras, the greenish-yellow light, is due to oxygen molecules. Also, typically auroras occur at higher altitudes in parts of Alaska, Norway, among other regions.
It is rare to see auroras at low latitudes
"The aurora lights were seen due to an intense geomagnetic storm that hit the Earth," said the Indian Institute of Astrophysics on Twitter. "It is extremely rare to see the aurora at such a low latitude." Located at Hanle, Ladakh, the 360-degree camera atop IAO, which operates at about 3,000 meters above sea level, captured the unique auroral display on April 22-23.
What caused the geomagnetic storm?
The actual cause of the geomagnetic storm was a coronal mass ejection (CME) erupting from the Sun on April 21. CMEs are explosions of plasma and magnetic fields from the Sun's outermost layer, called the corona. While CMEs cause beautiful auroras, they can also disrupt navigation systems and produce geomagnetic-induced currents (GICs) in power grids.
The fastest CMEs can reach Earth in about 15-18 hours
CMEs travel at speeds ranging from slower than 250 km/s to as fast as about 3,000 km/s, per the National Oceanic and Atmospheric Administration. The fastest CMEs can take about 15-18 hours to reach our planet. The CME which struck Earth on the night of April 22-23 had a speed of 21,60,000 km/hr, said Wageesh Mishra, assistant professor at the IAO.
The auroral display could be seen from Europe and China
Mishra added that the auroras occurred at latitudes lower than usual and that the rare spectacle could have been observed from Europe, China, and Ladakh in India. The previous time when such an intense geomagnetic storm struck Earth was in 2015.
