Astronomers have turned to a solar tsunami to measure the Sun’s magnetic field, according to a press release from the University College London.

This particular solar tsunami was first spotted by NASA’s Solar Dynamics Observatory (SDO) and the Japanese Hinode spacecraft.

Solar tsunamis are produced by gigantic explosions in the Sun’s atmosphere known as coronal mass ejections (CMEs). Earth-directed CMEs can cause a space weather phenomenon called a geomagnetic storm. As the sun’s activity increases toward solar maximum in late 2013, strong storms are expected to occur more frequently.

The solar tsunami can move across the Sun at speeds as fast as 1000 kilometers per second.

Just like the tsunamis that travel across the Earth are shaped by the planet’s oceans, the shape of solar tsunamis are determined by the environment through which they move. Solar tsunamis, for example, move faster in regions of stronger magnetic field.

This property gave astronomers the chance to measure the Sun’s magnetic field. Interestingly, astronomers discovered the Sun’s atmosphere has a magnetic field that is approximately ten times weaker than a normal fridge magnet.

An instrument on the Japanese Hinode spacecraft, called the Extreme ultraviolet Imaging Spectrometer, helped astronomers obtain information that was used to measure the density of the solar atmosphere through which the tsunami was moving.

Lead author David Long and his colleagues point out that the combination of imaging and spectral data gives astronomers a chance to analyze the magnetic field which pervades the Sun’s atmosphere.

According to Long, the Sun’s magnetic field is observable as loops and other structures in the Sun’s atmosphere. However, he adds that directly measuring the Sun’s atmosphere is hard and usually has to be guessed at by using computer simulations.

The Hinode spacecraft has three extremely sensitive telescopes, which utilize visible, X-ray and ultraviolet light to observe both slow and quick changes in the Sun’s magnetic field.

The telescopes help astronomers track how the magnetic field around sunspots is generated, shapes itself, and then fades away. These findings reveal just how observant these telescopes are, detecting magnetic fields that were previously believed to be way too weak to spot.

The explosions that generate solar tsunamis can send CMEs flying toward Earth. Despite its own magnetic field, the Earth is susceptible to solar storms because they can impact our satellites.

NASA recorded video of a solar tsunami in 2012. In the video, hot waves of charged gas could be seen arcing away from the Sun in colossal red loops.

The study’s findings are described in detail in the journal Space Physics.