Helio- and Asteroseismology

INTRODUCTION  | OBSERVATIONS : the SUN  | OBSERVATIONS : STARS  | MODELS  | SOLAR OSCILLATIONS  | RESULTS 
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Oscillations on the solar surface

The oscillations on the solar surface are characterized by the total number of node lines l (which is also called the degree) and the number m of nodes along the equator (also called the azimuthal order). Here we show two examples, with images that can be activated into a film by clicking. Points on the surface that have a velocity outwards are shown in blue, and points with a velocity inwards are shown in red (corresponding to the Doppler effect).

The second example is a little misleading : in reality the oscillations with m different from 0 correspond to waves, that run around the Sun, as shown in this version of the film. This effect enables us to study the solar rotation using the oscillations : waves that move in the same direction as the rotation look as if they have a slightly higher frequency, and waves moving against the rotation look as if they have a somewhat lower frequency. This effect is very similar to the Doppler effect.

However, it is easier to see what happens by following the waves around the Sun, and that is what we are doing in the following cases.

In reality the Sun oscillates with a very large number of modes simultaneously. Even the effect of adding just three modes with different amplitudes and frequencies becomes quite complicated. The effect is shown here : every image activates a small film that shows the oscillation :

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When there are over 100,000 oscillations at the same time the analysis to disentangle them is very complex.

The BiSON group has made a website where you can make and see a film of the oscillation pattern for a given oscillation. To do so, click on the referring link and follow the instructions.