An extremely rare phenomenon, the result of large waves vibrating in the Earth’s magnetic field that are triggered by the impact of solar particles, has been recorded by an astrophotographer from Iceland: the formation of “aurora clusters”.
Jeff Dai spotted the zigzag light show over Kerid Crater Lake on January 16, according to the website Spaceweather.com. As he reported in an Instagram post, the unusual phenomenon lasted several minutes before disappearing completely.
Auroras are created when highly energetic particles from the Sun surpass Earth’s magnetic field (magnetosphere) and excite gas molecules, which emit colorful lights as a result. Typically, these dancing light trails rotate randomly across the night sky with no defined shape or pattern.
What are aurora curls?
“Aurora clusters” are a rare, highly formatted version of these lights caused by significant ripples in the magnetosphere known as ultra-low frequency (ULF) waves.
These magnetic tremors are most commonly triggered by a blast of radiation from the Sun (solar wind) colliding with our planet’s protective shield and can cause the atmosphere to “ring like a bell.”
Normally invisible, ULF waves are detected only by scientific instruments that are perfected in Earth’s upper atmosphere. In this case, however, the pulsations allowed solar radiation to penetrate the magnetosphere and create a singular band of light that took on a wavy shape.
“Imagine that Earth’s magnetic field is like a guitar string,” said Xing-Yu Li, an expert on ULF waves at Peking University in China. “In the image, we are seeing vibrations in this string.”
It’s not entirely clear what kind of waves created the aurora clusters because the magnetic tremors were not picked up by scientific equipment. Based on the images, Li estimates that the magnetic pulsations had a wavelength of about a kilometer.
Both auroras and ULF waves are more common during periods of high solar activity. The Sun is near the peak of its current activity cycle of approximately 11 years – a peak known as solar maximum. At this stage, solar storms become more frequent and powerful, and the star triggers more intense bursts of solar wind. This increases the chances of seeing more clusters of aurora in the coming years.