Geomagnetic indices ASY-H and SYM-H and their relation to interplanetary parameters

The dependences of the geomagnetic indices SYM-H and ASY-H on interplanetary parameters for the period from 1981 to 2015 according to their daily averages are studied. The study is carried out in two ways: the first — the entire data array is analyzed, the second — the data are divided into 9 activity groups in accordance with the average daily values of the planetary geomagnetic index Ap. A correlation analysis of the indices with the solar wind speed, magnitude, and the north-south component of the interplanetary magnetic field (IMF) has been performed. The search for a relationship between the ASY-H and SYM-H indices and interplanetary parameters turned out to be more successful when considering the entire data array than in the case of splitting the data into groups of magnetic activity. Regression equations relating ASY-H and SYM-H to interplanetary parameters are determined. It has been found that when describing the relationship between the ASY-H and SYM-H indices and the IMF north-south component, it is necessary to take into account the contribution of the IMF modulus.