Tonga’s 2022 eruption created a very rare ‘plasma super bubble’ in the ionosphere: ScienceAlert

With technology increasingly incorporated into our everyday lives, it is increasingly important to understand space weather and its impacts on technology.

When you hear “space weather”, you usually think of huge explosions on the Sun – coronal mass ejections hurtling towards Earth, creating beautiful displays of auroras.

However, not all space weather starts on the Sun.

The volcanic eruption in Tonga in January 2022 was so massive that it created ripples in the upper atmosphere that constituted its own form of space weather.

It was one of the biggest explosions in modern history and impacted GPS in Australia and Southeast Asia. As we describe in our new study in the journal space weatherthe eruption caused a super “plasma bubble” in northern Australia that lasted for hours.

A truly global positioning system

Although most people have a GPS (global positioning system) receiver in their devices (such as satnavs and smartphones), not many people know how GPS actually works.

In essence, our devices listen to radio signals transmitted by satellites orbiting Earth. Using these signals, they calculate your location relative to the satellites, allowing us to orient ourselves and find that nearby bar or cafe.

The radio signals received by our devices are affected by the Earth’s atmosphere (particularly the layer called the ionosphere), which degrades the location accuracy. Ordinary devices are only accurate to within tens of meters.

However, new and improved accurate satellite positioning systems used in the mining, agriculture and construction industries can be accurate to within four inches. The only problem is that these systems need time to lock in your location, and that can take thirty minutes or more.

This precise satellite positioning works by accurately modeling the errors caused by the Earth’s ionosphere. But whenever the ionosphere is disturbed, it becomes complicated and difficult to model.

For example, when a geomagnetic storm (a disturbance in the solar wind that affects the Earth’s magnetic field) occurs, the ionosphere becomes turbulent and the radio waves passing through it scatter – like visible light which bends and scatters. when looking down on a lake in choppy conditions.

a volcanic rupture

Recent studies have shown that the eruption of the Hunga Tonga-Hunga Ha’apai volcano caused erratic conditions in the ionosphere that lasted for a few days. The size of the waves generated in the ionosphere were similar in size to those created by geomagnetic storms.

While these waves influenced GPS data around the world for days after the eruption, their impact on positioning was quite limited compared to another type of disturbance in the ionosphere – a “plasma super bubble” that formed after the eruption.

The ionosphere is a layer of Earth’s atmosphere at altitudes of approximately 80 to 800 kilometers (50 to 500 miles). It is composed of gas with many electrically charged particles, which makes it a “plasma”.

In turn, equatorial plasma bubbles are disturbances of plasma in the ionosphere that occur naturally at night above low latitude regions.

These plasma bubbles occur regularly. They form due to a phenomenon called “generalized Rayleigh-Taylor instability”. It’s similar to what happens when a heavy fluid sits on top of a less heavy fluid, and bubbles from that lighter fluid rise into the heavy fluid in the form of “bubbles” (see video below).

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When it comes to disturbances in the ionosphere, however, plasma is also controlled by magnetic and electric fields.

As they rise, the plasma bubbles form oddly shaped structures that resemble cacti or inverted tree roots. Due to Earth’s magnetic field, these structures spread out as the bubble grows above the equator.

The result is that higher altitude bubbles also reach higher latitudes. Typically, plasma bubbles reach a few hundred kilometers above the equator, reaching latitudes between 15 and 20 degrees north and south.

A rare blob above Australia

Scientists detected a super bubble of plasma above Southeast Asia shortly after the Tonga eruption. It is estimated to be similar in size to the previously reported rare super bubbles.

Earth’s magnetic field drove this disturbance south, where it remained for a few hours above Townsville in northeastern Australia.

To date, this is the southernmost point that any plasma bubbles have been observed in Australia. Although very rare, these superbubbles are known to have occurred in northern Australia, but were not observed directly prior to this event.

The deployment of GPS stations in northern Australia has only recently made this type of observation possible.

It is understood that the waves from the volcano eruption disturbed the winds in the upper atmosphere, altering the flow of plasma in the ionosphere and giving rise to the plasma super bubble.

Our study found that the bubble caused significant delays in the use of accurate GPS across Northern Australia and Southeast Asia. In some cases, getting a lock on the GPS location took more than five hours due to the plasma bubble.

Although we understand a lot about the ionosphere, our ability to predict its disturbances is still limited. Having more GPS stations is not only beneficial to improve positioning and navigation, but also fills gaps in ionosphere monitoring.

The Tonga eruption was far from a typical “space weather” event caused by the Sun. But its impact on the upper atmosphere and GPS highlights the importance of understanding how the environment affects the technologies we depend on.

Brett Carter, Associate Professor, RMIT University; Rezy Pradipta, Senior Research Fellow, Boston College, and Suelynn Choy, Professor

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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