A wonderfully smooth and confusing Christmas Day breaking Dawn It was the result of the ‘rainstorm’ observed over the Arctic in 2022 electrons directly Sunsay researchers based in Japan and the US.
This is the first time a rare aurora of this type has been seen from the ground, at a time when the winds are blowing. solar wind had almost completely disappeared, leaving a calm region around the Earth.
Normally aurora displays are similar to those seen around the world In Maymoves and pulsates in clearly distinguishable patterns across the sky. These auroral displays are powered by electrons from the solar wind, a stream of charged particles flowing from the sun, and these electrons get compressed into a Earth’s magnetic field It is called magnetotail. When space weather when it becomes excessive, for example, Coronal mass removal When a CME — a massive pulse of plasma and magnetic field from the sun — is released, the magnetotail can be torn off (don’t worry, it will grow back). The electrons trapped there flow down SoilThey move magnetic field lines toward the poles. As they do this, they encounter molecules. Earth’s atmospherecolliding with them makes them shine Colors of the Aurora (blue for nitrogen emissions, green or red for oxygen depending on altitude).
But the soft aurora on December 25-26, 2022, was very different. Imaged by an All-Sky Electron Multiplying Charge-Coupled Device (EMCCD) camera in Longyearbyen, Norway, the aurora was a faint, featureless glow spanning 2,485 miles (4,000 kilometers) across. It had no structure, pulsations, or changing brightness. No aurora of this type has ever been seen from Earth before.
To solve the mystery, a team led by Keisuke Hosokawa of the Center for Space Science and Radio Engineering at the University of Electro-Communications in Tokyo compared this faint aurora with what the Special Sensor Ultraviolet Survey Imager (SSUSI) on the polar-orbiting satellite of the Defense Meteorological Satellite Program (DMSP) sees. DMSP is operated by the National Oceanic and Atmospheric Administration and the United States. Space Force On behalf of the United States Department of Defense.
Satellites have seen the polar shower aurora from above and found that it has all the characteristics of a rare type of aurora called polar shower auroras, previously visible only from space.
The regular solar wind moves at about 250 miles (400 km) per second. However, the sun’s hot corona It is full of holes, especially at high solar latitudes, where an extraordinarily ‘fast’ solar wind flows at speeds of up to 500 miles (800 km) per second. Occasionally, these coronal holes can appear at lower latitudes, and this is exactly what happened around Christmas 2022, when the regular solar wind stops.
Where coronal holes are located, the sun’s magnetic field lines are open — they do not return to the sun’s surface, the photosphere. As the open magnetic field lines extend out into space, the coronal hole forms the bottom of a magnetic funnel through which high-energy electrons flow.
In the polar rain aurora, these electrons moved through space and open magnetic field lines combined with the Earth’s magnetic field above the north pole, allowing electrons to rain down directly onto the poles rather than getting trapped in the magnetotail.
Normally we don’t notice this happening because the regular polar wind particles scatter the fast-wind electrons coming out of the coronal hole. But this time, the pressure of the solar wind had decreased to a negligible level, and the fast-wind electrons were able to reach Earth unimpeded.
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Furthermore, the diameter of this magnetic funnel opening is estimated to be approximately 4,600 miles (7,500 km). Distance of Earth from the SunThis is why the aurora appeared so smooth; open tubes of magnetic flux emanating from the sun covered an area larger than the Earth’s north polar cap. Because the electrons were so energetic, the auroral emission was entirely green rather than red, as more energy was needed to ionize oxygen deep in the atmosphere.
The definitive proof was that the DMSP satellites only saw the polar shower aurora over Earth’s north magnetic pole, which is tilted toward the Sun during the Northern Hemisphere winter.
“When the solar wind disappeared, an intense electron flux with energy >1keV was observed by the DMSP. This made the polar shower aurora visible as bright greenish emissions even from the ground,” Hosokawa’s team wrote in the published research paper.
The polar rain has previously been studied in depth by particle detectors. satellites in orbit, but such studies are few and far between. These smooth auroras are normally invisible to the naked eye on the ground. So until now, no one knew what the smooth, featureless aurora that painted the sky green around Christmas 2022 was. A full description can be found in the June 21 issue of the journal Science is Advancing.