The ongoing volcanic eruption in Tonga began in December 2021, but it was not until 5:15 p.m. local time on January 15, 2022 that the powerful explosion occurred.
It generated a huge cloud of ash, earthquakes and tsunamis that reached the distant coasts of Peru across the Pacific.
Now scientists are even researching the effects of the eruption in space.
The eruption column reached Earth’s stratosphere, the second layer of the atmosphere from the ground. The sound of the explosion was heard thousands of miles away Yukon Territory, Canada. And although below the threshold of human hearing, pressure (sound) waves have even been detected by barometers UK.
It looks like the rash also seems to have generated a series of so-called “atmospheric gravity waves”, which were detected by a NASA satellite, radiating outward from the volcano in concentric circles.
Scientists, including me, are now trying to see what impact these waves can have in space.
The goal of our research is to better understand the upper levels of the atmosphere, well above the orbit of the International Space Station (ISS), and in particular to what extent changes therein are driven by events on Earth (as opposed to the space environment).
It could also help us better understand how technology like GPS is affected by volcanic eruptions.
Because the atmosphere is mostly transparent to human eyes, we rarely think of it as a complex, dynamic structure with several distinct layers. The upper tendrils of our atmosphere extend well above the karman lineage, the point 100 km (62 miles) above sea level where space officially begins.
These atmospheric layers are full of waves moving in all directions, much like the waves on the surface of the sea. atmospheric gravity waves can be generated by a number of phenomena, including geomagnetic storms caused by explosions on the Sun, earthquakes, volcanoes, thunderstorms and even sunrise.
You have probably seen some of the effects yourself, because these same waves can create rolling clouds.
These waves don’t just travel horizontally, they also travel upwards to some of the highest parts of our planet’s atmosphere – the ionosphere.
It is a region of the Earth’s atmosphere that extends from about 65 km to more than 1,000 km (the ISS orbits at about 400 km). At these altitudes, atmospheric gases are partially ‘ionized’, forming what is called a plasma, which means that its molecules are split into charged particles – positive atoms called ions and negative electrons.
Ionization in the atmosphere occurs due to exposure to ultraviolet radiation from the Sun, high energy particles from space, and even burning meteors.
But since oppositely charged particles exert an attractive force on each other, like a magnet stuck to a refrigerator door, ions and electrons also tend to recombine, again producing neutral molecules.
There is therefore a complex and continuous fluctuation in the ionosphere between the production of plasma and the loss of plasma due to recombination.
Although these processes are mostly undetectable in visible light, they can affect longer wavelength radio light. Plasma in the ionosphere can reflect radio waves at some frequencies, scatter them at others, or even block them entirely.
These properties make the ionosphere useful for several modern technologies, including high frequency radio communications, and radar above the horizon.
But just like at ground level, the ionosphere is subject to weather conditions. This is caused either by the spatial environment (space weather) or by events on Earth.
When atmospheric gravity waves generated by a volcanic eruption (or any other source) reach the ionosphere, they can trigger what is called “traveling ionospheric disturbances“.
They are compression waves that can dramatically increase plasma density fluctuations in a short period of time and can travel thousands of miles around the globe. These effects can disrupt modern technology, for example by interfering with the accuracy of satellite-based Global Positioning Systems (GPS).
To study these disturbances in more detail than their effects on GPS, I use data from a facility called the Low frequency network (Lofar). One of the largest radio telescopes in the world, Lofar consists of dozens of radio antennas spread across Europe, designed to observe distant natural radio sources in the early Universe, such as radio galaxies.
The appearance of radio sources in space, when viewed through the ionosphere, is similar to how the view of objects through a glass of water can become distorted as we stir (or shake) mount it.
With careful analysis, one can use these distortions to understand what is happening in the ionosphere itself. Traveling ionospheric disturbances can enhance these distortions, especially at the radio wavelengths we use with Lofar.
the video above (and seen here), created by Richard Fallows, shows Lofar data from December 2013. Bright bright spots are natural radio sources such as distant galaxies. The sequence in the left panel is from a calm night and in the right panel the ionosphere is disturbed. The springs can be seen rapidly changing position and fading.
Over the next few weeks we will be looking very carefully at our Lofar data to determine if there are any distinct patterns visible that could be attributed to the Tonga eruption.
Ultimately, the research could help us better understand how volcanoes on Earth influence space and technology.
As the ionosphere is the atmospheric interface between Earth and space, it can even illuminate the precise degree to which disturbances are caused by terrestrial weather events relative to space.