A possible correlation between solar activity and Earth's oblateness
Recent observations demonstrate that Earth's dynamic oblateness (J2), which has exhibited a decrease since 1979, suddenly increased around 1997 and the increase is still continuing. The decrease is attributed to post-glacial rebound from the mantle, and several causes, all of terrestrial nature, have been suggested to explain the sudden change in the trend. But the observations remain puzzling. On the other hand, close relationships are known to exist between many phenomena on the Earth with solar activity, and unusual behaviours of other planets have also been demonstrated to be correlated with solar activity. We show here that solar activity is significantly correlated with J2, and is possibly responsible for the sudden increase in Earth's dynamic oblateness around 1997, the latter being due to an enormous increase in the correlation.
I would think changing the shape of the earth would have an effect on the magnetic field
FYI