Science

NASA ICON découvre les effets de l’éruption volcanique massive des Tonga dans l’espace

Le satellite GOES-17 a capturé des images d’un nuage parapluie généré par l’éruption sous-marine du volcan Hunga Tonga-Hunga Ha’apai le 15 janvier 2022. Des ondes de choc en arc en forme de croissant et de nombreux éclairs sont également visibles. Crédit : Image de l’Observatoire de la Terre de la NASA par Joshua Stevens utilisant l’imagerie GOES avec l’aimable autorisation de la NOAA et du NESDIS

Quand les Hunga Tonga-Hunga Ha’apai le volcan est entré en éruption le 15 janvier 2022, il a envoyé des ondes de choc atmosphériques, des bangs soniques et des vagues de tsunami dans le monde entier. Maintenant, les scientifiques découvrent que les effets du volcan ont également atteint l’espace.

Analyse des données de Ionospheric Connection Explorer de la NASAou ICON, mission et les satellites Swarm de l’ESA (l’Agence spatiale européenne), les scientifiques ont découvert que dans les heures qui ont suivi l’éruption, des vents à la vitesse d’un ouragan et des courants électriques inhabituels se sont formés dans l’ionosphère – la couche atmosphérique supérieure électrifiée de la Terre à la périphérie de l’espace.

“Le volcan a créé l’une des plus grandes perturbations spatiales que nous ayons vues à l’ère moderne”, a déclaré Brian Harding, physicien à[{” attribute=””>University of California, Berkeley, and lead author on a new paper discussing the findings. “It is allowing us to test the poorly understood connection between the lower atmosphere and space.”

Hunga Tonga Hunga Ha’apai Eruption Illustration

The Hunga Tonga-Hunga Ha’apai eruption on January 15, 2022, caused many effects, some illustrated here, that were felt around the world and even into space. Some of those effects, like extreme winds and unusual electric currents were picked up by NASA’s ICON mission and ESA’s (the European Space Agency) Swarm. Image not to scale. Credit: NASA’s Goddard Space Flight Center/Mary Pat Hrybyk-Keith

ICON launched in 2019 to identify how Earth’s weather interacts with weather from space – a relatively new idea supplanting previous assumptions that only forces from the Sun and space could create weather at the edge of the ionosphere. In January 2022, as the spacecraft passed over South America, it observed one such earthly disturbance in the ionosphere triggered by the South Pacific volcano.

“These results are an exciting look at how events on Earth can affect weather in space, in addition to space weather affecting Earth,” said Jim Spann, space weather lead for NASA’s ICON to Explore Boundary Between Earth and Space

Illustration of ICON spacecraft. Credits: NASA’s Goddard Space Flight Center/Mary Pat Hrybyk-Keith

In the ionosphere, the extreme winds also affected electric currents. Particles in the ionosphere regularly form an east-flowing electric current – called the equatorial electrojet – powered by winds in the lower atmosphere. After the eruption, the equatorial electrojet surged to five times its normal peak power and dramatically flipped direction, flowing westward for a short period.

“It’s very surprising to see the electrojet be greatly reversed by something that happened on Earth’s surface,” said Joanne Wu, a physicist at University of California, Berkeley, and co-author on the new study. “This is something we’ve only previously seen with strong geomagnetic storms, which are a form of weather in space caused by particles and radiation from the Sun.”

Swarm Constellation

ESA’s constellation of three Swarm satellites is designed to identify and measure precisely different magnetic signals. This will lead to new insight into many natural processes, from those occurring deep inside the planet, to weather in space caused by solar activity. Credit: ESA/ATG Medialab

The new research, published today (May 10, 2022) in the journal Geophysical Research Letters, is adding to scientists’ understanding of how the ionosphere is affected by events on the ground as well as from space. A strong equatorial electrojet is associated with redistribution of material in the ionosphere, which can disrupt GPS and radio signals that are transmitted through the region.

Understanding how this complex area of our atmosphere reacts in the face of strong forces from below and above is a key part of NASA research. NASA’s upcoming Geospace Dynamics Constellation, or GDC, mission will use a fleet of small satellites, much like weather sensors on the ground, to track the electrical currents and atmospheric winds coursing through the area. By better understanding what affects electrical currents in the ionosphere, scientists can be more prepared to predict severe problems caused by such disturbances.

Reference: “Impacts of the January 2022 Tonga Volcanic Eruption on the Ionospheric Dynamo: ICON-MIGHTI and Swarm Observations of Extreme Neutral Winds and Currents” by Brian J. Harding, Yen-Jung Joanne Wu, Patrick Alken, Yosuke Yamazaki, Colin C. Triplett, Thomas J. Immel, L. Claire Gasque, Stephen B. Mende and Chao Xiong, 10 May 2022, Geophysical Research Letters.
DOI: 10.1029/2022GL098577