British astrophysicists report they've used a solar "tsunami" observed by U.S. and Japanese spacecraft to measure the sun's magnetic field.

Solar tsunamis such as the one observed by NASA's Solar Dynamics Observatory and the Japanese Hinode spacecraft are produced by enormous explosions in the sun's atmosphere called coronal mass ejections that spew masses of particles into space while the tsunami travels across the sun at speeds of as much as 2,200 mph.

Researchers at University College London said tracking the tsunami across the sun's surface allowed them to make the first accurate estimates of the sun's magnetic field.

Visible as loops and other structures in the solar atmosphere, the sun's magnetic field is difficult to measure directly, they said, but imaging and spectral observations from the two spacecraft allowed them to examine both slow and rapid changes in the magnetic field and make estimates of its strength.

"We've demonstrated that the sun's atmosphere has a magnetic field about 10 times weaker than a normal fridge magnet," lead researcher David Long said in a UCL release Thursday.

"These are rare observations of a spectacular event that reveal some really interesting details about our nearest star," Long said of the solar tsunamis.