Planetary Modulation of Solar Activity

It has recently been shown that the planet Mercury exerts a small control on relative sunspot numbers, the degree of control depending on the positions of the other planets. This paper describes the results of extending the work to include all the planets. As a working hypothesis we have assumed that gravitational tidal forces induced on the Sun by the planets may modulate solar activity and have accordingly calculated relative equilibrium ‘high tide’ displacements of the solar surface for each day from the positions, masses and distances of the first six planets. Although the tides are very slight, the mass of displaced material is appreciable and varies over the very wide range of nearly 5 to 1.