Solar tsunami helps measure Sun's magnetic field accurately

WASHINGTON: NASA's Solar Dynamics Observatory (SDO) and the Japanese Hinode spacecraft have observed a solar tsunami to provide the first accurate estimates of the Sun's magnetic field.

Solar tsunamis are produced by enormous explosions in the Sun's atmosphere called coronal mass ejections (CMEs).

As the CME travels out into space, the tsunami travels across the Sun at speeds of up to 1000 kilometres per second.

Similar to tsunamis on Earth, the shape of solar tsunamis is changed by the environment through which they move.

Just as sound travels faster in water than in air, solar tsunamis have a higher speed in regions of stronger magnetic field.

This unique feature allowed the team, led by researchers from UCL's Mullard Space Science Laboratory, to measure the Sun's magnetic field.

Dr David Long, UCL Mullard Space Science Laboratory, and lead author of the research, said: "We've demonstrated that the Sun's atmosphere has a magnetic field about ten times weaker than a normal fridge magnet."

Using data obtained using the Extreme ultraviolet Imaging Spectrometer (EIS), a UK-led instrument on the Japanese Hinode spacecraft, the team measured the density of the solar atmosphere through which the tsunami was travelling.

The combination of imaging and spectral observations provides a rare opportunity to examine the magnetic field which permeates the Sun's atmosphere.

The findings are set to be published in the journal Solar Physics.