Astronomers Spot a Mysterious Blue Aurora That Could Be Indicating Some Unknown Atmospheric Processes
In May 2024, a blue aurora captivated humans with its stunning glow but intrigued researchers because of its unique features. The phenomenon took place due to an intense magnetic storm and was observed at low altitudes, Science Alert reported.
The catch was auroras that are observed at low altitudes usually appear red because of the oxygen emissions but this one sported a salmon-pink color all through the night and a blue color shortly before midnight. While the aurora was blue, it was also unusually tall. In a recent study published in Earth, Planets and Space researchers concluded that this peculiarity took place that day because of a yet-unknown atmospheric process.
Auroras facilitate on Earth because of the huge influx of solar particles from the sun in the form of coronal mass ejection or solar wind. If Earth somehow comes in their path, as they travel through the Solar System, they clash with the magnetic field. In the magnetic field, the particles are diverted as well as accelerated and can be dropped anywhere in the atmosphere. Interaction with the Earth's gases causes the particles to get energized, and when they begin to lose that extra energy, photons start to get ejected. The glow is the result of this release.
To analyze the particular aurora that happened in May, the study used images captured by citizen scientists in Japan. The team found that the particular aurora was placed in longitudinal structures across magnetic lines. There were three separate structures, and throughout its period of activity, the aurora managed to achieve flight between the heights of 400 and 900 kilometers.
The researchers claim that the blue-dominant aurora was a result of nitrogen molecular ions somehow managing to move to higher altitudes. As to how these nitrogen molecular ions managed to do so, remains a mystery.
"Our findings suggest that nitrogen molecular ions may have accelerated upward by some mechanism and were responsible for the formation of the blue-dominant aurora," co-author Kazuo Shiokawa of Nagoya University explained, Science Alert reported.
"To date, it is not well understood how nitrogen molecular ions with large molecular weight can exist at such high altitudes. Such ions are not easily able to exist for long periods of time due to their heavy mass and short dissociative-recombination time intervals; however, they are observed at high altitudes. The process is shrouded in mystery," said Shiokawa.
Researchers also are unsure that like other low-altitude auroras, this one was associated with ring current. The ring current is a torus-shaped structure containing charged particles that circle the Earth's equator. Low-altitude aurora typically facilitates when a geomagnetic storm energizes the energetic neutral atoms (ENAs) present inside the ring. But what Japan witnessed in May was somehow distinct.
"In this study, a structure of several hundred kilometers was found in the blue-dominant aurora in the longitudinal direction, which is difficult to interpret by ENA activity only," Shiokawa added. "In addition, ENAs are unlikely to create auroral structures aligned with magnetic field lines, as observed in this study."
The study states that if ring current was involved it worked in collaboration with the activity of nitrogen molecular ions to produce the particular aurora. It is not possible for the ring current to solely produce blue hues of such stature in the atmosphere.
Researchers are aiming to figure out the atmospheric process responsible for the supposed acceleration of nitrogen ions. The team is hopeful that repeated occurrences of blue auroras will continue to happen and give them more data to come to an accurate conclusion.
"As solar activity increases in the coming years," the researchers write, "repeated case analyses of such blue-dominant auroras are expected to provide insights into the generation processes of blue-dominant low-latitude auroras."