Scientists directly observe electron dynamics of the Northern Lights

February 14, 2018, University of Tokyo
The ERG spacecraft observed chorus waves and scattered electrons in the magnetosphere, the origin of pulsation auroras. The scattered electrons precipitated into the atmosphere resulting in auroral illumination. Intermittent occurrence of chorus waves and associated electron scattering lead to auroral pulsation. Credit: 2018 ERG science team.

The shower of electrons bouncing across Earth's magnetosphere, commonly known as the Northern Lights, has been directly observed for the first time by an international team of scientists. While the cause of these colorful auroras has long been hypothesized, researchers had never directly observed the underlying mechanism until now. The results have been published in Nature.

The spectacle of the Northern Lights is a fantastic show widely considered to be one of the great natural wonders of the world. Among a variety of auroras, pulsating auroral patches appearing at dawn are common, but the physical mechanisms driving this auroral pulsation were never verified through observation.

With a new satellite carrying advanced measuring tools, researchers have now identified that this phenomenon is caused by the hard-to-detect interaction between and plasma waves. This interaction takes place in the Earth's magnetosphere, the region surrounding the Earth in which the behavior of the electric particles is usually governed by the planet's magnetic field.

"Auroral substorms are caused by global reconfiguration in the magnetosphere, which releases stored ," writes Satoshi Kasahara, an associate professor at the University of Tokyo in Japan, the lead author of the paper. "They are characterized by auroral brightening from dusk to midnight, followed by violent motions of distinct auroral arcs that eventually break up, and emerge as diffuse, pulsating auroral patches at dawn."

Pulsating aurora, the origin of the blinking patches of light, is now directly observed by the ERG spacecraft. Electrons in the magnetosphere, which usually bounce along the geomagnetic field, are thought to be scattered by chorus waves, resulting in precipitation into the atmosphere. The intermittent bursts of chorus waves cause the pulsations of precipitation and associated auroral illumination. The ERG spacecraft showed that this electron scattering by chorus waves indeed takes place in the magnetosphere. Credit: 2018 ERG science team.

The global reconfiguration often drives a specific type of plasma wave called chorus waves to rain electrons into the upper atmosphere. This stabilizes the system, and gives off a colorful light as the electrons fall. However, scientists have questioned if the chorus waves were powerful enough to excite electrons to the extent of creating auroras.

"For the first time, we have directly observed scattering of electrons by chorus waves generating particle precipitation into the Earth's atmosphere," Kasahara says. "The precipitating electron flux was sufficiently intense to generate pulsating aurora."

Scientists couldn't see this direct evidence of electron scattering before because typical electron sensors cannot distinguish the precipitating electrons from others. Kasahara and his team designed a specialized electron sensor that detected the precise interactions of auroral electrons driven by . The sensor was aboard the Exploration of Energization and Radiation in Geospace (ERG) satellite, also known as the Arase spacecraft, launched by the Japan Aerospace Exploration Agency.

The scientists plan to pursue this line of research further. "By analyzing data collected by the ERG spacecraft more comprehensively, we will reveal the variability and further details of plasma physics and resulting atmospheric phenomena, such as auroras," Kasahara says.

Explore further: FIREBIRD II and NASA mission locate whistling space electrons' origins

More information: S. Kasahara et al, Pulsating aurora from electron scattering by chorus waves, Nature (2018). DOI: 10.1038/nature25505

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Kalopin
1 / 5 (2) Feb 14, 2018
...auroras are a direct result from solar flares... [charged particles from excessive blasts of solar winds, stemming from CMEs, usually the result of a cometary impact...]

""Auroral substorms are caused by global reconfiguration in the magnetosphere, which releases stored solar wind energy," writes Satoshi Kasahara, an associate professor at the University of Tokyo in Japan, the lead author of the paper..."
...how often does he believe the magnetosphere reconfigures itself?...
[I believe he is mistaken]
...that, and the fact that it is very obvious that as soon as there is a solar eruption in this direction then there is an excess in aurora borealis...
[...and eruptions, earthquakes, stronger weather patterns..., ...which is what has been occurring due to the recent debris field this solar system has recently entered..., ...from the neutron star collision...;-]
cantdrive85
1 / 5 (4) Feb 14, 2018
The scattered electrons precipitated into the atmosphere resulting in auroral illumination.

"Precipitated" electrons... Whatever you do, never, ever admit to electric currents actually doing anything of consequence anywhere for any reason....
Kalopin
1 / 5 (2) Feb 14, 2018
"...Solar wind forms the energy source for aurora explosions. How does the Earth's magnetosphere take in the energy of the solar wind? An international team led by Hiroshi Hasegawa and Naritoshi Kitamura (ISAS/JAXA) analyzed data taken by the US-Japan collaborative mission GEOTAIL and NASA's MMS satellites and revealed that the interaction between the magnetic fields of Earth and the Sun, or more precisely the phenomenon known as magnetic reconnection, can feed the aurora explosions..."

Read more at: https://phys.org/...html#jCp
cantdrive85
1 / 5 (5) Feb 14, 2018
Magnetic reconnection is pseudoscience, the energy is delivered via electric currents and surface interactions such as sheaths and double layers.
Kalopin
5 / 5 (2) Feb 14, 2018
https://www.nasa....nnection "...Reconnection occurs wherever charged gases, called plasma, are present. It's rare on Earth, but plasma makes up 99% of the visible universe. Plasma fuels stars and fills the near vacuum of space. Plasmas behave unlike what we regularly experience on Earth because they travel with their own set of magnetic fields entrapped in the material. Changing magnetic fields affect the way charged particles move and vice versa, so the net effect is a complex, constantly-adjusting system that is sensitive to minute variations
Under normal conditions, the magnetic field lines inside plasmas don't break or merge with other field lines. But sometimes, as field lines get close to each other, the entire pattern changes and everything realign into a new configuration. The amount of energy released can be formidable. Magnetic reconnection taps into the stored energy of the magnetic field, converting it into heat and kinetic energy"
Kalopin
1 / 5 (1) Feb 14, 2018
...the magnetosphere doesn't actually "store" long term energy, the pressure is being steadily built up and released... [right?;-]
cantdrive85
1 / 5 (4) Feb 15, 2018
Plasmas behave unlike what we regularly experience on Earth because they travel with their own set of magnetic fields entrapped in the material.

Frozen-in field descriptions are pseudoscientific claptrap.
But sometimes, as field lines get close to each other...

More pseudoscientific claptrap. And field lines cannot break or merge, just more claptrap.

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