Saturday, May 05, 2007

SOHO & Sun Ripples

The Solar and Heliospheric Observatory (SOHO) may have glimpsed long-sought oscillations on the Sun’s surface.

The subtle variations reveal themselves as a miniscule 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.

The so-called ‘g-modes’ are driven by gravity and provide information about the deep interior of the Sun. They are thought to occur when gas churning below the solar surface plunges even deeper into our star and collides with denser material, sending ripples propagating through the Sun’s interior and up to the surface. It is the equivalent of dropping a stone in a pond.

Unfortunately for observers, these waves are badly degraded during their passage to the solar surface. By the time g-modes reach the exterior, they are little more than ripples a few metres high.

Until now, the rotation rate of the solar core was uncertain. If the the Global Oscillation at Low Frequency (GOLF) - instrument on SOHO -detection is confirmed, it will show that the solar core is definitely rotating faster than the surface.

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

The next step for the team is to refine the data to increase their confidence in the detection, by incorporating data from other instruments, both on SOHO and at ground-based observatories.

SOHO's quest for solar ripples from ESA
A Massive Explosion on the Sun from NASA

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