Does this mean the 7 degree tilt of the solar axis precesses at a steady rate to a complete cycle around every 25920 years? This figure is very close to being the same as the earth’s precessionary cycle. Are the two geometrically aligned in any way? i.e. do the tilts ‘point in the same direction? If so, what could be the cause of this? Some sort of magnetic coupling? Or the gravitation of a distant mass such as the galactic centre?

The main point is that as far as we know, none of this has anything to due with climate change at the surface.

The problem lies in the phrase ‘as far as we know’. The speedy collapse of temperatures in the stratosphere when sunspots fail to appear is testimony to the importance of UV light in ionospheric and stratospheric processes. The collapse of the F layer shows that the ionic population is depleted when the solar wind impacts the magnetosphere. With it goes, to some extent, the neutrals. Hence, density change due to lateral movement. That will affect UV penetration. The atmosphere has no sharp boundaries. The impact of UV light, that is responsible for the temperature inversion at 100hPa in the tropics, must be felt below 100hPa for that inversion to manifest. The pressure difference between 200hPa and 100hPa is indicative of the difference in the density of material and the amount that separates these two levels. You don’t have to be Einstein, have a pHd in Physics or be a mathematical whiz to work this out.

You will have to select for 2.5Mb and the early years. Radiosondes to not appear to go this far. Do you know of other sources? Agreed, more data is is vital.

We report on periodic oscillations in thermosphere density, measured by the accelerometer on the CHAMP satellite during 2006, and relate these periodicities to oscillations observed in solar wind speed and Kp index.

My understanding is that in the ionosphere movement of material (ionic and entrained neutrals) is due to magnetic polarity and reactions to change in magnetic fields is fast. Aurora provide evidence of energy and density increase, together with warming, above the poles. The material has to come from somewhere. I suggest that it is drawn from equatorial regions. The F layer can disappear above the equator.

The 7% should be 7 degrees and is the tilt angle of the Sun’s axis. The explanation of the semiannual change you describe is called the ‘axial’ explanation and was first formulated by Cortie in 1912. The mechanism is responsible for a small part [~10% on average] of the semiannual variation of geomagnetic activity that is observed.

Yes, I meant 7°. Would you mind briefly listing the other sources of the semi-annual variation. Does the coupling factor account for the rest? Can we agree that temperature variations at 2.5hPa as shown for a couple of early years at http://discover.itsc.uah.edu/amsutemps/execute.csh?amsutemps show evidence of this effect by virtue of a displacement of the annual peak from January to March?