Volcanic eruptions shown to disrupt satellite comms links

The ionosphere is the region of the Earth’s upper atmosphere where molecules and atoms are ionised by solar radiation, creating positively charged ions.

The area with the highest concentration of ionised particles is called the F-region, an area 150 to 800km above the Earth’s surface. This region plays a crucial role in long-distance radio communication, reflecting and refracting radio waves used by satellite and GPS tracking systems back to the Earth’s surface.

But according to scientists at Nagoya University in Japan, these transmissions can be disrupted by irregularities in the F-region. During the day, the ionosphere is ionised by the sun’s ultraviolet radiation, creating a density gradient of electrons with the highest density near the equator.

However, disruptions to this, which are known as an equatorial plasma bubble (EPB), can create areas of highly dense plasma which can delay radio waves and degrade the performance of GPS.

The researchers looked at the Tonga volcano eruption last year, which was the biggest submarine eruption in history. To test their theory, the team used the Arase satellite to detect EPB occurrences, the Himawari-8 satellite to check the initial arrival of air pressure waves and ground-based ionospheric observations to track the motion of the ionosphere.

They observed an irregular structure of the electron density across the equator that occurred after the arrival of 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. 

The group also made a surprising discovery. For the first time, they showed that ionospheric fluctuations start a few minutes to a few hours earlier than the atmospheric pressure waves involved in the generation of plasma bubbles when it was previously thought that this occurred after the eruption.

“Our new finding is that the ionospheric disturbances are observed several minutes to hours before the initial arrival of the shock waves triggered by the Tonga volcanic eruption,” Shinbori said.

“This suggests that the propagation of the fast atmospheric waves in the ionosphere triggered the ionospheric disturbances before the initial arrival of the shock waves. Therefore, the model needs to be revised to account for these fast atmospheric waves in the ionosphere.”

They also found that the EPB extended much further than predicted by the standard models.

“Previous studies have shown that the formation of plasma bubbles at such high altitudes is a rare occurrence, making this a very unusual phenomenon,” Shinbori said. “We found that the EPB formed by this eruption reached space even beyond the ionosphere, suggesting that we should pay attention to the connection between the ionosphere and the cosmosphere when extreme natural phenomena, such as the Tonga event, occur.”

The study could help to prevent satellite broadcasting and communication failures associated with ionospheric disturbances caused by earthquakes, volcanic eruptions, and other events – times when the technology is most relied upon in order to aid in rescue efforts.