  Using recent data obtained by Advanced Composition Explorer (ACE) the pumping
scale of the magnetic field gradients of the solar wind plasma has been
calculated. This pumping scale is found to be equal to 24h $\pm$ 2h. The ACE
spacecraft orbits at the L1 libration point which is a point of Earth-Sun
gravitational equilibrium about 1.5 million km from Earth. Since the Earth's
magnetosphere extends into the vacuum of space from approximately 80 to 60,000
kilometers on the side toward the Sun the pumping scale cannot be a consequence
of the 24h-period of the Earth's rotation. Vise versa, a speculation is
suggested that for the very long time of the coexistence of Earth and of the
solar wind the weak interaction between the solar wind and Earth could lead to
stochastic synchronization between the Earth's rotation and the pumping scale
of the solar wind magnetic field gradients. This synchronization could
transform an original period of the Earth's rotation to the period close to the
pumping scale of the solar wind magnetic field gradients.
