Characteristics of the Geoeffective Component of the Interplanetary Magnetic Field

The characteristics of the southward component of the interplanetary magnetic field (IMF) component in GSM coordinate system, Bs, within 1990--2017 for different solar activity levels are presented. We show that Bs ordered according to the polarity (Bs polarity fields) exhibit a "pair of spectacles" pattern, the two annual sinusoidal-like variations of opposite phase.It means that Bs polarity fields exist for toward/away field in fall/spring ("unfavorable" seasons). These fields are reduced, but are not zero. Thus, in "unfavorable" seasons, geomagnetic activity can be due to reduced Bs and not because the field is northward pointing.This study provides a new and deep inside into the pattern of experimental Bs which differs from previous models. In this way this research contributes in better understanding of the origin of Bs, which is the important IMF component in controlling the reconnection process and therefore highly influences the perturbation in the Earth's magnetosphere.