News Feature | January 19, 2022

Did The Tonga Volcano Eruption Disrupt The Ionosphere, Affect GPS?

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By Abby Proch, Editor

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As experts on many fronts are still grappling with the immediate effects of the ongoing Tonga volcano explosion, others are pondering the extent — and distance — of its impact. Namely, could the eruption have degraded GPS positioning accuracy or even disrupted the Earth’s ionosphere?

It’s possible, explains Garreth Dorrian in a recent article in The Conversation.  

According to Dorrian, the eruption on Jan. 15 set off a series of Earth-bound events like earthquakes and tsunamis, but it also produced what’s called atmospheric gravity waves. Rippling outward and upward in concentric circles, these waves are now being studied by scientists wondering how their presence might affect the top-most layers of the Earth’s atmosphere: the ionosphere.

Situated 65km to 1,000km from the Earth’s surface, the ionosphere typically experiences an ebb and flow of plasma production and recombination. This constant fluctuation cannot be seen but is measured in its ability to reflect, scatter, and even block radio waves. The climate there is prime for over-the-horizon radar and high-frequency radio communications. But since weather can always become a disrupter, gravitational waves — becoming travelling ionospheric disturbances — are also potential disrupters.

That’s where LOFAR will come in handy. Low Frequency Array (LOFAR) is the world’s largest radio telescope, developed in the Netherlands and capable of operating at the lowest frequencies observable on Earth. Dorrian, and likely others, will be using LOFAR data to compare quiet nights with those occurring soon after the volcanic eruption, looking for anomalies in the ionosphere.  What he’ll also consider is how the effects from an earth-bound event may differ from those initiated in space.

If past events are an indicator, there’s a good chance the Tonga eruption(s) produced disturbances to GPS data, even momentarily. For example, ionospheric perturbations on GPS data were recorded after the 1994 Northridge earthquake in Southern California, as published by researchers in Science Direct. And in 2012, the NASA Jet Propulsion Laboratory recorded GPS aberrations following a March 2011 tsunami in Japan.