Killer electrons in strumming sky lights

Killer electrons in strumming sky lights
Low-energy (blue) and high-energy (yellow) electrons form during the process that generates the pulsating aurora. The high-energy ‘relativistic’ electrons could cause localized destruction of the ozone. Credit: PsA project

Computer simulations explain how electrons with wide-ranging energies rain into Earth’s upper and middle atmosphere during a phenomenon known as the pulsating aurora. The findings, published in the journal Geophysical Research Letters, suggest that the higher-energy electrons resulting from this process could cause destruction of the part of the ozone in the mesosphere, about 60 kilometers above Earth’s surface. The study was a collaboration between scientists in Japan, including at Nagoya University, and colleagues in the US, including from NASA.


The northern and southern lights that people are typically aware of, called the aurora borealis and australis, look like colored curtains of reds, greens, and purples spreading across the night skies. But there is another kind of aurora that is less frequently seen. The pulsating aurora looks more like indistinct wisps of cloud strumming across the sky.

Scientists have only recently developed the technologies enabling them to understand how the pulsating aurora forms. Now, an international research team, led by Yoshizumi Miyoshi of Nagoya University’s Institute for Space-Earth Environmental Research, has developed a theory to explain the wide-energy electron precipitations of pulsating auroras and conducted computer simulations that validate their theory.

Their findings suggest that both low- and high-energy electrons originate simultaneously from interactions between chorus waves and electrons in the Earth’s magnetosphere.

Chorus waves are plasma waves generated near the magnetic equator. Once formed, they travel northwards and southwards, interacting with electrons in Earth’s magnetosphere. This interaction energizes the electrons, scattering them down into the upper atmosphere, where they release the light energy that appears as a pulsating aurora.

The electrons that result from these interactions range from lower-energy ones, of only a few hundred kiloelectron volts, to very high-energy ones, of several thousand kiloelectron volts, or ‘megaelectron’ volts.

Miyoshi and his team suggest that the high-energy electrons of pulsating auroras are ‘relativistic’ electrons, otherwise known as killer electrons, because of the damage they can cause when they penetrate satellites.

“Our theory indicates that so-called killer electrons that precipitate into the middle atmosphere are associated with the pulsating aurora, and could be involved in ozone destruction,” says Miyoshi.

The team next plans to test their theory by studying measurements taken during a space rocket mission called ‘loss through auroral microburst pulsations’ (LAMP), which is due to launch in December 2021. LAMP is a collaboration between NASA, the Japan Aerospace Exploration Agency (JAXA), Nagoya University, and other institutions. LAMP experiments will be able to observe the killer electrons associated with the pulsating aurora.

The paper, “Relativistic Electron Microbursts as High‐Energy Tail of Pulsating Aurora Electrons,” was published online in Geophysical Research Letters on October 13, 2020.


Pulsating aurora mysteries uncovered with help from NASA’s THEMIS mission


More information:
Y. Miyoshi et al. Relativistic Electron Microbursts as High‐Energy Tail of Pulsating Aurora Electrons, Geophysical Research Letters (2020). DOI: 10.1029/2020GL090360
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Northern lights shimmer over Arctic amidst dazzling display

“Usually you have to go a little ways out of town to get away from those city lights [to see them],” said Ryan Medzger, a meteorologist at the Fairbanks Weather Service office, who called the display “impressive.”

Other shots captured across the Final Frontier showed arcing bands of light splayed out across the sky like fluttering glow-in-the-dark wind chimes.

The lights were courtesy of a solar storm, or an eruption of high-energy particles from the surface of the sun. That burst of electromagnetic radiation hurtled toward the earth, where it reached the threshold of a level 2 out of 5 “geomagnetic storm.” The earth’s natural magnetic field converts that potentially hazardous energy into harmless visible light.

In the case of Saturday’s episode, the source of the energy wasn’t one prolific burst of energy, but rather a stream of solar wind emanating from a “coronal hole.” That’s a cooler region on the surface of the sun out of which the solar wind pours, sending a swift stream of energetic particles into space.

Some photographers even snagged shots of elusive “corona” formations, not to be confused with the solar corona, or the outer layer of the sun’s atmosphere. The term comes from the Latin word for “crown” and describes whirlpool-like curls of the northern lights that pinch off and, from below, appear like a crown of converging blades of light.

In Fairbanks, the scene was accompanied by rare “light pillars,” or vertical columns of light above the ground.

Light pillars form when extremely cold air causes hexagonally-shaped ice crystals to be present near the surface. Light reflects off their lower horizontal faces and toward an observer, causing light to appear as a vertical stripe.

A glimpse of the northern lights was seen as far south as northern Minnesota and Wyoming, while some colors were even spotted from the northern United Kingdom. Meanwhile, the full splendor of the aurora appeared over Scandinavia, with stunning shots coming in from Norway, Sweden and Finland.

In Iceland, the aurora was bright enough to be seen even from the streets of Reykjavik, the nation’s capital

The Suomi NPP/VIIRS satellite, which stands for Visible Infrared Imaging Radiometer Suite, is able to detect and resolve sources of light, including from the northern lights. The satellite was peering down on Alaska when the sky erupted in color as a 300-mile-wide band of aurora descended from the high Arctic. Meteorologists were able to obtain a view from space as tendrils of plasma writhed their serpentine weave.

The northern lights are most common at the peak of the solar cycle, which falls every 11 years or so. When the cycle is in full gear, the number of sunspots, or bruiselike discolorations on the sun, are at a maximum. These sunspots throb with energy and are typically the origin of the “coronal mass ejections” that bring aurora to earth.

At present, we’re in “solar minimum,” during which the sun can be spotless for long stretches of time. That makes such epic displays of

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Rocket Booster Likely Caused Lights in Hawaii’s Night Sky | Hawaii News

HONOLULU (AP) — Reports of a cluster of blinking lights traveling across Hawaii’s weekend night sky were likely caused by a rocket booster reentering the planet’s atmosphere, scientists said.

Astronomers said there is a high probability the booster pierced Earth’s atmosphere after orbiting for 12 years, The Honolulu Star-Advertiser reported Tuesday.

Spectators posted photos and videos on social media of the lights that appeared Saturday night.

The booster identified by scientists was used to launch Venezuela’s communications satellite VENESAT-1 from China in October 2008.

The booster was in a low orbit and eventually slowed and reentered the atmosphere at about 10 p.m., said Roy Gal, associate astronomer of the Institute for Astronomy at the University of Hawaii at Manoa.

An aerospace company tracked and predicted the reentry of the booster, which correlated with Saturday’s reentry window, Gal said.

Some observers thought they may have spotted Starlink satellites launched by Space Exploration Technologies Corp., better known as SpaceX, the company found by Billionaire Elon Musk that has sent broadband internet satellites into orbit.

Others wondered whether they saw a meteor shower or a UFO.

What residents actually saw was the rocket body heating during reentry and breaking into pieces, Gal said.

“The friction from the atmosphere makes it glow and burn,” Gal said.

The Canada-France-Hawaii Telescope atop Mauna Kea captured an image of the rocket booster streaking across the sky.

John O’Meara, chief scientist of the W.M. Keck Observatory, said the booster traveled at more than 20,000 mph (32,187 kph) before it disintegrated over the Pacific Ocean.

“Space junk” enters the atmosphere all the time, O’Meara said.

“We just usually don’t see it because we’re not in the right space to see it,” O’Meara said.

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Watch: Lights in Hawaii sky believed to be from 12-year-old rocket booster

Oct. 26 (UPI) — Experts said bright lights spotted in the sky over Hawaii were likely the remnants of a booster from a rocket launched 12 years ago.

John O’Meara, chief scientist of the W. M. Keck Observatory in Waimea, said the lights spotted in the sky Saturday night likely were from the booster of a Chinese rocket launched in 2008.

Mary Beth Laychak, strategic communications director for the Canada France Hawaii Telescope, said the appearance of the lights lines up with projections of the booster’s re-entry path.

“We can’t be 100% certain because we don’t have any of the pieces of the debris,” Laychak told KHON-TV. “But the pattern of the lights that we saw in our time lapse combined with this map.”

“This flight path and the precision at which all of these companies are able to estimate where their objects will enter and how they’ll break up is what really leads us to believe that this was this Venesat-1 re-entering the atmosphere,” she said.

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