Tonga eruption disrupted satellite signals

2023-05-23 11:00:34

An air pressure wave caused by volcanic eruptions can cause an equatorial plasma bubble (EPB) in the ionosphere, severely disrupting satellite communications.

The finding, the result of satellite and terrestrial ionospheric observations on the occasion of the explosive eruption of the Tonga volcano in January 2021, was published in the journal Scientific Reports ⁽¹⁾.

The ionosphere is the region of Earth’s upper atmosphere where molecules and atoms are ionized by solar radiation, creating positively charged ions. The area with the highest concentration of ionized particles is called the F region, an area 150 to 800 kilometers above the Earth’s surface. The F region plays a crucial role in long-distance radio communication, reflecting and refracting radio waves used by GPS and satellite tracking systems back to Earth’s surface.

These important transmissions can be interrupted by irregularities in the F region. During the day, the ionosphere is ionized by ultraviolet radiation from the Sun, creating an electron density gradient with the highest density near the equator. However, disruptions to this, such as plasma motion, electrical fields, and neutral winds, can cause a localized irregularity of enhanced plasma density to form. This region can grow and evolve, creating a bubble-like structure called an EPB. EPB can delay radio waves and degrade GPS performance.

A perfect opportunity to test this theory

Since these density gradients can be affected by atmospheric waves, it has long been hypothesized that they are shaped by terrestrial events such as volcanic activity.

For an international team led by Nagoya University’s Institute for Space-Earth Environmental Research (ISEE), the Tonga volcano eruption offered a perfect opportunity to test this theory.

The Tonga volcano eruption was the largest underwater eruption in history. This allowed the team to test their theory using the Arase satellite to detect EPB occurrences, the Himawari-8 satellite to verify the initial arrival of air pressure waves, and ground-based ionospheric observations to track the movement of the ionosphere. They observed an irregular pattern of electron density along the equator that occurred after the arrival of the pressure waves generated by the volcanic eruption.

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

The group also made a startling discovery. For the first time, they showed that ionospheric fluctuations start a few minutes to a few hours before the atmospheric pressure waves involved in the generation of plasma bubbles. This could have important implications because it suggests that the geosphere-atmosphere-cosmosphere coupling model, which states that ionospheric disturbances only occur after the eruption, needs revision.

It reached space even beyond the ionosphere

“Our new finding is that ionospheric disturbances are observed several minutes to hours before the initial arrival of shock waves from the Tongan volcanic eruption,” Shinbori said. “This suggests that the propagation of 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 was extended far beyond what was provided by standard models. “Previous studies have shown that the formation of plasma bubbles at such high altitudes is somewhat uncommon, which makes it a very unusual phenomenon,” Shinbori said. “We found that the EPB formed by this eruption reached into space even beyond the ionosphere, suggesting that we need to pay attention to the connection between the ionosphere and the cosmosphere when extreme natural phenomena occur, such as the Tonga event.”

“The results of this research are significant not only from a scientific point of view but also from the point of view of space weather and disaster prevention,” he said. “In the case of a large-scale event, such as the eruption of the Tonga volcano, observations have shown that a hole in the ionosphere can form even under conditions considered unlikely under normal circumstances. Such cases have not been incorporated into the space. weather forecast models. This study will contribute to the prevention of satellite communication and transmission failures associated with ionospheric disturbances caused by earthquakes, volcanic eruptions and other events.”

References

• ⁽¹⁾Generation of equatorial plasma bubble after the 2022 Tonga volcanic eruption. Scientific Reports.