A global gravity oscillation determined by superconducting gravimetry measurements and astronomical latitude observations

Abstract

A global gravity long-period nontidal oscillation is determined by means of superconducting gravimeter data from the Brussels Observatory and latitude observations from zenith telescope at the Plana Observatory in Bulgaria. The used gravimetry data from Brussels consists of a few series one-hour normal values of the measurements between 1982 and 2000. The time series are filtered and the non-tidal variations of the gravity at the Brussels Observatory are derived. The non-tidal variations of the gravity at Brussels consist of instrumental drift, seasonal oscillations, polar tides and a long-period oscillation with an amplitude of about 50 nm/s2. A similar long-period oscillation is detected in the variations of the vertical in the meridian plane at Plana in Bulgaria by means of the latitude observations from zenith telescope since 1987. The amplitude of this oscillation of the vertical at the Plana Observatory is about 0.01 arcsec.