The Intense Auroral Activity Captures at Hanle and Merak in Ladakh

 Due to the intense geomagnetic storms arising from Coronal Mass Ejections from the Sun impacting the Earth the intense auroral activity was captured by cameras at the Indian Astronomical Observatory in Hanle and Merak in Ladakh on the night of 10-11 May. The observatories at Hanle and Merak have All-sky Cameras that image the entire sky constantly. Strong aurorae were predicted to occur and were indeed seen from across the globe at much lower latitudes than usual. It is pertinent to mention that the Observatory is run by the Indian Institute of Astrophysics (IIA), an autonomous institute under the Department of Science and Technology, Govt of India.

At least four such solar storms reached the Earth between 10 and 11 May, giving rise to extraordinary aurora worldwide, even at low latitudes. These were caused by as many super-strong Coronal Mass Ejections that were launched from the Sun between 8-9 May 2024, which were directed towards the Earth. The Earth’s magnetic field has been disturbed for several hours now, and the intensity of this perturbation, measured by the “peak Dst index”, was -412 nT on 11 May 2024. The last such intense storm occurred in November 2003, with a Dst index of -422 nT. The index is usually around zero in the absence of storms, and a typical storm has an index of about -50 to -100 nT. Extreme geomagnetic storms have the potential to harm space-technology-dependent human life on Earth, such as disrupting radio communication, GPS signals, etc. Predicting these storms is an important area of scientific research at IIA and many other institutions as well.

It is to be noted that Aurorae occur due to the interaction between the Earth’s magnetosphere and the incoming solar wind that carries charged particles and magnetic fields, and are more intense when ‘geoeffective’ solar storms hit the Earth. In general, the aurorae are seen from higher latitudes, and therefore not seen from India. Only in the case of extremely strong solar storms, do countries at lower latitudes get to see them. The recent set of storms was one such event where it could be witnessed from India at Ladakh.

“The Hanle Dark Sky Reserve and surrounding regions, with its high altitude and dark skies, is an excellent location to see aurora from such intense storms which are visible even at such low latitudes”, said Niruj Mohan Ramanujam from IIA. Stable Auroral Red arcs were photographed from Hanle and Merak during a previous solar storm on the night of 5-6 November 2023 as well.

 “The red auroral light could be captured by Hanle camera towards the northern horizon from half past midnight till about morning twilight, and peaked around 2 AM”, said Dorje Angchuk, the Engineer-in-Charge of the Observatory at Hanle. A similar camera at Merak, on the banks of Pangong Tso, which is the proposed site of the National Large Solar Telescope, also captured the aurora. Apart from intense red colour caused by energetic particles in the upper atmosphere, blue- and violet-coloured bands were also seen, which are due to particles that extend even lower into our atmosphere.

“These four CMEs were also associated with strong M and X types of solar flares from the active region AR13664 and were observed by NASA’s SOHO/LASCO spacecraft on 8 May 11:50 IST with the speed of around 500 km/s, on 9 May 00:30 IST with speed of 500 km/s, on 9 May 15:30 IST with speed as high as 1900 km/s, and the fourth on 10 May 00:30 IST with speed of 1200 km/s”, said Wageesh Mishra, a solar astronomer at IIA. 

The flares were also observed in the optical waveband at Kodaikanal Solar Observatory and Merak and in the radio waveband at the Gauribidanur Radio Observatory and Kodaikanal. These CMEs travelled toward the Earth and reached the Earth on 10-11 May at a speed of around 700 km/s. The shock driven by these storms reached Earth on 10 May at 22:22 IST with a speed of around 815 km/