July 11, 2013
Solar Tsunami Offers Rare Measurement Of Sun’s Magnetic Field
Lee Rannals for redOrbit.com - Your Universe Online
A solar tsunami has provided scientists with the first accurate estimates of the Sun's magnetic field. Researchers wrote in the journal Solar Physics that solar tsunamis are produced by enormous explosions in the Sun's atmosphere known as coronal mass ejections (CMEs). As these events move through space, the tsunami travels across the Sun at speeds of up to 621 miles per second.
Solar tsunamis have a higher speed in regions where the magnetic field is stronger, similar to how sound travels faster in water than in air. And like oceanic counterparts, the shape of these solar tsunamis is changed by the environment they move through, giving scientists the ability to measure the Sun's magnetic field.
"We've demonstrated that the Sun's atmosphere has a magnetic field about ten times weaker than a normal fridge magnet," says Dr David Long of University College London Mullard Space Science Laboratory, lead author of the study.
The team used data taken by an instrument on the Japanese Hinode spacecraft to measure the density of the solar atmosphere through which the tsunami was traveling. Together with observations provided by NASA's Solar Dynamics Observatory (SDO), this data provided an opportunity to examine the magnetic field.
"These are rare observations of a spectacular event that reveal some really interesting details about our nearest star," Long said.
The Sun's magnetic field is difficult to measure directly and usually has to be estimated using computer simulations. The Hinode spacecraft has three highly sensitive telescopes which use the visible, X-ray and ultraviolet spectrum to examine slow and rapid changes in the magnetic field.
Instruments on Hinode act like a microscope to track how the magnetic field around sunspots is generated, shapes itself and then fades away. These results show how sensitive these instruments can be, measuring magnetic fields that were previously believed to be too weak to detect.
Explosions on the Sun can send CMEs hurtling towards Earth, creating space weather that can have adverse effects on orbiting satellites and Earth-bound technological infrastructure.
"As our dependency on technology increases, understanding how these eruptions occur and travel will greatly assist in protecting against solar activity," Long said.
NASA's SDO has been instrumental in helping scientists understand more about the Sun. The spacecraft has a constant eye on our neighboring star and can view the monstrous object in multiple wavelengths. In April NASA released a video of the unbroken coverage of the sun for the past three years. It is data like this that allows researchers like Long to continue opening up the door to understanding the Sun.