Astronomers finally catch glimpse of elusive solar ripples

The ESA/NASA Solar and Heliospheric Observatory (SOHO) has finally managed to catch a glimpse of the long sought oscillations, g-modes, on the Suns surface.

Washington, May 4 : The ESA/NASA Solar and Heliospheric Observatory (SOHO) has finally managed to catch a glimpse of the long sought oscillations, g-modes, on the Sun's surface.

The variations reveal themselves as a minuscule ripple in the overall movement of the solar surface. Astronomers have been searching for ripples of this kind since the 1970s, when they first detected that the solar surface was oscillating in and out.

Driven by gravity, the oscillations provide information about the deep interior of the Sun.

Researchers believe the 'g-modes' occur when gas churning below the solar surface plunges even deeper into the Sun and collides with denser material, sending ripples propagating through the interior and up to the surface, equivalent to the ripple caused by dropping a stone in a pond.

Unfortunately, these waves are badly degraded during their passage to the solar surface. Also by the time they reach the exterior, they are little more than ripples a few metres high, and to make matters more difficult, they take between two and seven hours to oscillate just once.

So, astronomers face the problem of having to detect a swell on the surface that rises a metre or two over several hours. But now, using the Global Oscillation at Low Frequency (GOLF) instrument on SOHO, researches have finally caught glimpses of these oscillations.

Rather than look for an individual oscillation, the researchers looked for the signature of the cumulative effect of a large number of these oscillations.

"We looked for the cumulative effect of several g modes. We combined ten years of data from GOLF and then searched for any hint of the signal at 24 minutes. We must be cautious but if this detection is confirmed, it will open a brand new way to study the Sun's core," said Rafael A. Garc�a, DSM/DAPNIA/Service d'Astrophysique, France.

The scientists say if the GOLF detection is confirmed, it will show that the solar core is definitely rotating faster than the surface. Until now, the rotation rate of the solar core was uncertain.

Garcia said the rotation speed of the solar core is an important constraint for investigating how the entire Solar System formed, because it represented the hub of rotation for the interstellar cloud that eventually formed the Sun and all the bodies around it.

The data will reveal details about the very core of our central star and it contains clues as to how the Sun formed, 4.6 billion years ago, he said.

The next step for the team, according to him, is to refine the data to increase their confidence in the detection. To do this, they plan to incorporate data from other instruments, both on SOHO and at ground-based observatories.

"By combining data from space (VIRGO and MDI, on SOHO) and ground (GONG and BiSON) instruments, we hope to improve this detection and open up a new branch of solar science," Garc�a added.

ANI