Secular variation in the geomagnetic field in 1980-2000

A joint analysis of DGRF-80 (MAGSAT) and IGRF-00 (Oersted) models has made it possible to distinguish the linear part of geomagnetic field variations for 20 years. A model of the secular acceleration (of the second time derivative) for this interval has been obtained with the help of an additional satellite model of the secular variation for 2000. An obtained quadratic spatiotemporal model was compared with the data series at observatories. It has been indicated that the error of a model constructed using only satellite data is too large because of a jerk in 1991. A spatiotemporal model constructed using only data of observatories describe variations better but only for the regions with a sufficient data body. The errors over the southern Pacific reach hundreds of nanoteslas. A new approach to the joint usage of data of satellites and observatories is proposed. Such a technique of spatiotemporal analysis makes it possible to decrease averaged errors to several tens of nanoteslas on the entire time interval and for the whole surface of the globe including ocean regions.