Variations of interplanetary magnetic field on various long time-scales

The IDV index of geomagnetic activity is used by many researchers as a proxy of the interplanetarymagnetic field (IMF) strength B. Using the original multiscale regression (MSR) method based on wavelet transformation, we obtained a long series of B values starting from 1845. Then, based on the new 2.0 versions of the sunspot number and group sunspot number and using MSR method and this series as a reference, we reconstructed IMF strength B starting from 1610. Further extension of the reconstruction is associated with radiocarbon reconstructions of solar activity at a time-scale of up to several millennia. It is shown that in the last 3200 yr the IMF strength has been experiencing a downward trend of -(0.39 +/- 0.17) . 10(-3) nT.yr(-1).