Leif Svalgaard came up with this link in a discussion on wattsupwiththat.com which I found very interesting.
Some of my colleagues at Berkeley [Martin Fivian and Hugh Hudson] has analyzed the shape of the Sun using the RHESSI satellite date:
Here’s my reply:
Thanks for the link Leif. One of the things I find interesting from that press release is the rapidity with which the 6km high lumps around sunspots smooth out again to the average oblateness. The Sun’s outer layers are obviously very fluid and mobile, so it would be expected that any internal lumpiness raised by tidal or gravitational forces from orbiting bodies would be compensated for quite quickly at the surface in flows from the low mid latitudes to the equator, which might explain the shifting of sunspots towards the equator throughout the solar cycle.
The vertical tide on the Surface raised by the biggest of the orbiting bodies is only in the order of mm as you have pointed out before. However the horizontal tides are much bigger, in the order of hundreds of km. Much the same as the Moon’s tidal action on the Earth, it is the horizontal tides which will cause most of the rising and falling of the surface. Further analysis is showing that at perihelion, Mercury causes a much bigger horizontal tide on the sun than Jupiter does. So does the synodic variation of Earth and Venus. Work on quantifying these and looking at their periodicities and phasing is ongoing.
Leif further claimed that:
Any shifting around of the interior would introduce a quadrupolar moment which is not observed.
My reply was:
The constraint on the quadrupole moment (2+-0.4)10^-7 isn’t so tight as to be able to be definite about that. Quite small movements in the dense solar interior would set up much larger flows on the much less dense solar surface.
Tidal effects have been dismissed as too small to have any effect on the Sun in the past, but new research by Semi and others may change that view. I’m posting this thread to provide a place for discussion, however speculative at this stage, concerning the possible effects of tides raised by planets on the surface of the Sun.