A sunquake is a short-lived seismic disturbance in the Sun’s interior seen with some solar flares and coronal mass ejections (CME) as propagating ripples on the surface. Like earthquakes, sunquakes have the potential to help us understand conditions inside the Sun.
What is the secret behind the workings of sunquakes?
The answer might be hidden beneath the solar surface, suggesting a new study based on NASA’s Solar Dynamics Observatory (SDO) data.
Sunquakes observed in the form of expanding wave ripples on the Sun’s surface during solar flares represent packets of acoustic waves excited by flare impacts and traveling through the solar interior.
For decades, scientists believe that the magnetic forces generated by solar flares generate sunquakes. Solar flares were thought to dive down through the Sun’s surface and deep into its interior. But, new results, using data from NASA’s Solar Dynamics Observatory, have found something different.
In July 2011, SDO observed a sunquake with unusually sharp ripples emanating from a moderately strong solar flare. Scientists were able to track the waves that caused these ripples back to their source, using a technique called helioseismic holography. This technique, which used SDO’s Helioseismic and Magnetic Imager to measure how the solar surface was moving, has previously been used to track acoustic waves from various other sources in the Sun.
Instead of the waves traveling into the Sun from above, the scientists saw the surface ripples of a sunquake emerging from deep beneath the solar surface right after a flare occurred.
The results found that the acoustic source was around 700 miles below the Sun’s surface – not above the surface as previously was thought.
According to scientists, these waves were driven by a submerged source, which was somehow triggered by the solar flare in the atmosphere above. The new findings might help explain a long-standing mystery about sunquakes: why some of their characteristics look remarkably different from the flares that trigger them.
The results of this study offer a clue that the origin of sunquakes likely lurks beneath the surface. The scientists plan to continue searching for a mechanism by looking at other sunquakes to see if they have similarly submerged sources.
- Charles Lindsey et al. Submerged Sources of Transient Acoustic Emission from Solar Flares. DOI: 10.3847/2041-8213/abad2a