Details

Autor(en) / Beteiligte

• Harding, Brian J.
• Wu, Yen‐Jung Joanne
• Alken, Patrick
• Yamazaki, Yosuke
• Triplett, Colin C.
• Immel, Thomas J.
• Gasque, L. Claire
• Mende, Stephen B.
• Xiong, Chao

Titel

Impacts of the January 2022 Tonga Volcanic Eruption on the Ionospheric Dynamo: ICON‐MIGHTI and Swarm Observations of Extreme Neutral Winds and Currents

Ist Teil von

• Geophysical research letters, 2022-05, Vol.49 (9), p.n/a

Ort / Verlag

Washington: John Wiley & Sons, Inc

Erscheinungsjahr

2022

Quelle

Wiley Online Library

Beschreibungen/Notizen

• The eruption of the Hunga Tonga‐Hunga Ha'apai volcano on 15 January 2022 triggered atmospheric waves at all altitudes. The National Aeronautics and Space Administration Ionospheric Connection Explorer (ICON) and European Space Agency Swarm satellites were well placed to observe its impact on the ionospheric wind dynamo. After the Lamb wave entered the dayside, Swarm A observed an eastward and then westward equatorial electrojet (EEJ) on two consecutive orbits, each with magnitudes exceeding the 99.9th percentile of typically observed values. ICON simultaneously observed the neutral wind (90–300 km altitude) at approximately the same distance from Tonga. The observed neutral winds were also extreme (>99.9th percentile at some altitudes). The covariation of EEJ and winds is consistent with recent theoretical and observational results, indicating that the westward electrojet is driven by strong westward winds in the Pedersen region (∼120–150 km). These observations imply that the dynamo is a key mechanism in the ionospheric response to the Tonga disturbance. Plain Language Summary The January 2022 Tonga volcanic eruption caused atmospheric impacts around the world. As a natural experiment, it can be used to test our understanding of how the lower atmosphere affects space weather. Researchers are only beginning to document the chain of events post‐eruption, and this paper focuses on its impact on the generator that drives electric fields in near‐Earth space, a key part of space weather. This generator is driven by the atmosphere pushing charged particles across Earth's magnetic field. This usually creates a strong eastward current above the equator. When the Swarm A satellite coincided with the wave from Tonga, it observed that this current strengthened dramatically, then reversed. Although reversals are not unusual, this was the strongest reversal observed by Swarm since its 2013 launch, except for one large geomagnetic storm in 2015. Another satellite, the Ionospheric Connection Explorer, was luckily at the right time and place to observe related motions of the upper atmosphere, which were similarly extreme. These observations are shown to be consistent with our theoretical understanding of the generator. This study is important because it represents a critical test of atmosphere‐space interactions and implies that the Tonga eruption caused a major space weather event. Key Points Extreme thermospheric winds and ionospheric currents were observed in coordinated space/ground‐based measurements, 10 hours post‐eruption The westward electrojet current when the Lamb wave reaches the dayside is consistent with recent studies of the wind‐driven electrojet Observations of linked dynamo processes provide direct evidence of the space‐weather impacts of acute lower atmospheric forcing