Solar Tsunami Enables First Accurate Estimates of Sun's Magnetic Field

A tsunami observed on the Sun has been used to create the first accurate estimates of the star's magnetic field, according to a new study soon to be published in the journal Solar Physics.

Solar tsunamis are produced by enormous explosions in the Sun's atmosphere called coronal mass ejections (CMEs) and are capable of reaching speeds of up to 620 miles (1,000 kilometers) per second.

Furthermore, like tsunamis on Earth, those on the Sun are affected 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 - a unique feature that enabled the team, led by researchers from the University College London's Mullard Space Science Laboratory, to measure the Sun's magnetic field.

Based on their results, David Long, the lead author of the research, said the team was able to demonstrate "that the Sun's atmosphere has a magnetic field about 10 times weaker than a normal fridge magnet."

In addition, using data obtained with the Extreme ultraviolet Imaging Spectrometer (EIS), a United Kingdom-led instrument on the Japanese Hinode spacecraft, the team measured the density of the solar atmosphere the tsunami was traveling through.

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

Visible as loops and other structures in the Sun's atmosphere, the Sun's magnetic field is difficult to measure directly and usually has to be estimated using intensive computer simulations. However, the Hinode spacecraft has three highly sensitive telescopes that use visible, X-ray and ultraviolet light to examine both its slow and rapid changes.

Importantly, the explosions that produce solar tsunamis can send CMEs hurtling toward the Earth, putting satellites and technological infrastructure at risk.

 "As our dependency on technology increases," Long said, "understanding how these eruptions occur and travel will greatly assist in protecting against solar activity."