Mysterious aurora-like phenomenon 'STEVE' appears during strongest solar storm for more than half a decade
A bizarre, aurora-like phenomenon known as STEVE made several appearances across the United States and parts of the United Kingdom last week, after a powerful solar storm slammed into Earth without warning.
STEVE, also known as a "strong thermal emission velocity enhancement," is a rare phenomenon that was officially discovered in 2016. During STEVE, a long, thick ribbon of light — usually white, purple or green in color — appears to hang in the sky for up to an hour. Although it looks very similar to auroras, or northern lights, and often appears at the same time, STEVE is not an aurora.
On March 23, a surprise coronal mass ejection (CME) — a gargantuan, fast-moving blob of plasma and magnetic field released from the sun — erupted from a massive hole in the sun that was wider than 20 Earths. Astronomers did not see the stealthy storm coming because it traveled much slower than normal CMEs and was therefore almost impossible to track. The resulting geomagnetic storm on Earth was the most powerful for six years and triggered spectacular auroras across the globe.
Related: Blood-red aurora transforms into 'STEVE' before stargazer's eyes
The sneaky solar storm also triggered unusually widespread sightings of STEVE. The phenomenon was photographed in South Dakota, Washington state, Idaho, Montana (twice) and in Scotland in the U.K., and it may have been visible in other places as well, according to Spacewaether.com.
During auroras, highly energetic particles from solar storms and solar wind break through the planet's magnetic field, or magnetosphere, and excite molecules of gas in the upper atmosphere. This creates swirling lights that ebb and flow over time. But STEVE is not triggered by high-energy particles and can occur much further away from Earth's poles than auroras tend to appear — although scientists are still unsure why.
Instead, STEVE is caused by a river of hot plasma, or ionized gas, that breaks through Earth's magnetosphere and into the ionosphere thanks to magnetic disturbances during solar storms. This plasma travels at around 13,300 mph (21,400 km/h), which creates friction with the surrounding air and excites molecules to glow in the same way as an aurora. But the constant flow of plasma causes an unmoving visual phenomenon for an observer compared with the dancing lights of auroras.
STEVE can also be accompanied by streaking green lights, or "picket fences," that flash in the sky for around 30 seconds before disappearing. Experts believe these picket fences form in a similar way to auroras, but the streaking lights are not fully understood.
This is not the first time STEVE has made an appearance above North America. In August 2022, STEVE was spectacularly photographed after it emerged in the skies above southern Canada after another surprise solar storm hit Earth.
A vibrant, purple STEVE cuts across the night sky above above Badlands National Park in South Dakota during the late hours of March 23. (Image credit: Evan Ludes/Framed By Nature)
Harry Baker
Fri, March 31, 2023
A close-up of the red light streaking across the night sky.
A bright red streak of light appeared in the sky above parts of Scandinavia last week after a surprise solar storm smashed into Earth and triggered stunning auroras across the planet. But the bright red band was not an aurora — it was something much rarer.
The streak, which appeared as a river of hazy red light that stretched all the way across the night sky, was most prominently visible above Denmark. Astrophotographer Ruslan Merzlyakov snapped a spectacular shot of the peculiar light show on March 23 above Møns Klint, a set of limestone cliffs on the Danish island of Møn in the Baltic Sea.
The unusual phenomenon is known as a stable auroral red arc (SAR), but despite the name, it is not an aurora or particularly stable, according to Spaceweather.com. Instead, the light is emitted by oxygen molecules in the upper atmosphere that have become superheated by Earth's ring current system, a massive loop of electric current that surrounds our planet.
The SAR coincided with the most powerful geomagnetic storm to hit Earth for six years, which was triggered by a surprise coronal mass ejection — a gargantuan, fast-moving blob of plasma and magnetic field released from the sun — that was spat out of a massive hole in the sun wider than 20 Earths.
The SAR shines above limestone cliffs in Denmark.
During auroras, highly energetic particles from solar storms and solar wind bypass Earth's magnetic field, or magnetosphere, and excite molecules of gas in the upper atmosphere. This creates swirling, multicolor lights that ebb and flow over time. The various colors of light come from different atoms, which emit specific colors when excited.
During SARs, energy from the ring current system, which surrounds the magnetosphere, heats up the gas in the upper atmosphere and makes it glow like an aurora. For unknown reasons, only oxygen is heated up during a SAR, which means these phenomena always emit the exact same shade of red, according to Spaceweather.com.
SARs actually occur quite frequently, but they are normally invisible to humans because they are too faint and our eyes are poorly attuned to the wavelength of red light emitted by SARs, according to Spaceweather.com. Massive streaks like the one over Denmark only become visible when strong solar storms weaken the magnetosphere, which enables more heat from the ring current system to enter the upper atmosphere.
RELATED STORIES
—Solar storm smashes hole in Earth's magnetosphere, triggering extremely rare pink auroras
—Ultra-rare 'rainbow clouds' light up the Arctic Circle like auroras in stunning new photos
—Bright green laser lines shoot across night sky in Hawaii. What caused them?
The SAR over Denmark was not the only unusual light show observed during the recent solar storm. The aurora-like phenomenon STEVE, a large ribbon of colored light that hangs in the sky for up to an hour, was also visible across the United States and parts of the United Kingdom.
There is some evidence that STEVE and SAR arcs are related phenomena. In March 2015, skywatchers in New Zealand watched as a bright red SAR slowly transformed into a STEVE event over the course of about half an hour.
No comments:
Post a Comment