Eruption of Tonga underwater volcano found to disrupt satellite signals halfway around the world

A group of scientists from different countries used observations from satellites and ground-based equipment to show that volcanic eruptions can cause a wave of air pressure that leads to a disturbance in the ionosphere, creating a bubble of plasma near the equator. This bubble can cause big problems for communication satellites. The scientists shared their discoveries in a journal called Scientific Reports.

The ionosphere is a part of the upper atmosphere that gets charged by the Sun’s rays, creating positively charged particles. One specific area within the ionosphere, called the F-region, is located between 150 to 800 kilometers above the Earth’s surface and has the highest concentration of these charged particles. The F-region is important for long-distance radio communication because it can reflect and bend radio waves used by satellites and GPS systems back to Earth’s surface.

Transmissions that are crucial for communication can be affected by irregularities in the F-region. During the daytime, the Sun’s ultraviolet radiation ionizes the ionosphere, resulting in a gradient of electron density, with the highest density found near the equator. However, disruptions in this process, such as the movement of plasma, electric fields, and neutral winds, can lead to the formation of a localized irregularity with a higher density of plasma. This irregularity can grow and change over time, creating a bubble-like structure known as an EPB. EPBs can cause delays in radio waves and negatively impact the performance of GPS systems.

Scientists have believed for a while that terrestrial events like volcanic activity can impact these density gradients. To test this theory, an international team, led by Designated Assistant Professor Atsuki Shinbori and Professor Yoshizumi Miyoshi from the Institute for Space–Earth Environmental Research (ISEE) at Nagoya University, collaborated with researchers from NICT, The University of Electro-Communications, Tohoku University, Kanazawa University, Kyoto University, and ISAS. They saw the eruption of the Tonga volcano as an ideal chance to investigate this further.

The eruption of the Tonga volcano was an unprecedented event, being the largest submarine eruption ever recorded. This unique situation provided the team with an opportunity to put their theory to the test. They utilized various tools and observations to conduct their research. The Arase satellite was used to identify instances of EPB formation, the Himawari-8 satellite helped in monitoring the initial arrival of air pressure waves, and ground-based ionospheric observations enabled tracking the movement of the ionosphere. Through these observations, the team noticed an irregular pattern in the electron density near the equator. This pattern emerged following the arrival of the air pressure waves generated by the volcanic eruption.

“The results of this study showed EPBs generated in the equatorial to low-latitude ionosphere in Asia in response to the arrival of pressure waves caused by undersea volcanic eruptions off Tonga,” Shinbori said.  

In addition to their main findings, the research team made an unexpected discovery. They observed that fluctuations in the ionosphere actually begin a few minutes to a few hours prior to the atmospheric pressure waves that contribute to the formation of plasma bubbles. This finding challenges the existing understanding of the relationship between the Earth’s geosphere (solid Earth), atmosphere, and ionosphere. The traditional model suggested that ionospheric disturbances occur only after a volcanic eruption. However, this new evidence indicates that a revision to this model may be necessary to account for the earlier ionospheric fluctuations observed in this study.

In light of their research findings, Designated Assistant Professor Atsuki Shinbori commented, “We have discovered something new: the disturbances in the ionosphere were observed several minutes to hours before the initial shock waves from the Tonga volcanic eruption arrived. This indicates that the fast atmospheric waves traveling through the ionosphere were responsible for the ionospheric disturbances before the arrival of the shock waves. As a result, the existing model needs to be updated to include these fast atmospheric waves in the ionosphere.”

Furthermore, the researchers discovered that the equatorial plasma bubble (EPB) extended much farther than what standard models had predicted. This was an unexpected finding as previous studies indicated that the formation of plasma bubbles at such high altitudes was a rare event. Designated Assistant Professor Atsuki Shinbori emphasized the uniqueness of this phenomenon, stating, “The EPB generated by the Tonga volcano eruption extended into space beyond the ionosphere, which is highly unusual. This highlights the importance of considering the connection between the ionosphere and the cosmosphere when studying extreme natural events like the Tonga eruption.”

Designated Assistant Professor Atsuki Shinbori emphasized the broader implications of the research, stating, “The findings of this study hold significance not only for scientific understanding but also for space weather and disaster prevention. In the case of a large-scale event like the Tonga volcano eruption, our observations have revealed the formation of an ionospheric hole, even under conditions that are typically considered unlikely. These scenarios have not been incorporated into current space weather forecast models. Our research will contribute to the prevention of satellite communication and broadcasting failures caused by ionospheric disturbances resulting from earthquakes, volcanic eruptions, and similar events. It provides valuable insights for disaster preparedness and mitigation strategies.”