Atmospheric gravity perturbations measured by a groundbased interferometer with suspended mirrors

In this paper, we discuss the possibility of making geophysical measurements using the large-scale laser interferometrical gravitational wave antenna. An interferometer with suspended mirrors can be used as a gradiometer measuring variations of an angle between gravity force vectors acting on the spatially separated suspensions. We analyse the restrictions imposed by the atmospheric noises on the feasibility of such measurements. Two models of the atmosphere are invoked: a quiet atmosphere with a hydrostatic coupling of pressure and density and a dynamic model of moving region of the density anomaly (cyclone). Both models lead to similar conclusions up to numerical factors. Besides the hydrostatic approximation, we use a model of turbulent atmosphere with the pressure fluctuation spectrum ~f^-7/3 to explore the Newtonian noise in a higher frequency domain (up to 10 Hz) predicting the gravitational noise background for modern gravitational wave detectors. Our estimates show that this could pose a serious problem for realization of such projects. Finally, angular fluctuations of spatially separated pendula are investigated via computer simulation for some realistic atmospheric data giving the level estimate ~10^-11 rad Hz^-1/2 at frequency ~10^-4 Hz. This looks promising for the possibility of the measurement of weak gravity effects such as Earth inner core oscillations.