An updated and homogeneous world secular variation data base .1. Smoothing of the archaeomagnetic results

The available original archaeomagnetic world data on intensity and direction have been compiled and sorted according to geographical region. Then, after correcting them to correspond to a single site associated with each region (called a world site), they have been processed using the Gaussian statistic for the intensity (F) data and bivariate statistic for the declination (D) and inclination (I) data, to obtain smoothed values at regular time intervals. We include a discussion of the statistical methods used. We have limited the data to the last 20 centuries because the archaeomagnetic data alone do not allow us to go back further in the past. We have also excluded archaeomagnetic studies at world sites where the number of data is not sufficient to perform a statistical analysis. We obtained results at nine world sites for which the values of at least two of the three above-quoted parameters have been calculated at 25 year intervals from the beginning of our era. The results for each world site with their associated errors are given and discussed. The potential of this new set of world data, for improving our knowledge of the global terrestrial magnetic field (TMF) during the past 20 centuries, is sketched. These results will be completed in a second paper by analysing in the same way the data supplied for volcanic rocks and lake sediments.