The solar acceleration obtained by VLBI observations.

Aims. The three-dimensional acceleration vector of the solar system barycenter was estimated from VLBI delay observations. We also provide a first physical explanation for this acceleration vector. Methods. Two methods for the acceleration estimation were developed in the analysis of the global astrometric/geodetic VLBI observations. One is to take the solar acceleration vector as a global parameter that is to be directly estimated. The second method is to obtain the acceleration by fitting the solar velocity variation time series produced from the VLBI data analysis. Results. The results of these two methods are consistent with each other within their uncertainties. The acceleration vector derived from the first method is (7.47 ± 0.46, 0.17 ± 0.57, 3.95 ± 0.47) mm s^-1 yr^-1 in the Galactic Cartesian coordinate system. Conclusions. The Galactocentric component of the solar acceleration we obtained agrees well with the predicted value from the rotation movement of the Sun and has a high accuracy. The detected strong vertical component perpendicular to the Galactic plane may be important for the research of the Milky Way. [ABSTRACT FROM AUTHOR]