Influence of interplanetary parameters on the degree of symmetry of the ring current

The paper studies the influence of interplanetary factors on the degree of symmetry of the magnetospheric ring current. The geomagnetic indices SYM-H, ASY-H, and interplanetary parameters for the period 1981–2015 are considered. The indicator of the degree of symmetry of the ring current is the ratio SYM-H/ASY-H. Analysis is based on annual averages of geomagnetic and interplanetary parameters. This approach allows us to identify large-scale patterns. The relationships are examined of the degree of symmetry of the ring current and the indices SYM-H and ASY-H with the value B of the interplanetary magnetic field (IMF), the IMF north-south component Bn, and the solar wind velocity V. It is concluded that properties of magnetospheric ring currents are described by these indices more adequately when offsets in their values are taken into account than without regard for them. It is found that when offsets in ASY-H are considered the symmetric ring current prevails approximately twice over the asymmetric one for average conditions in the solar wind: V<550 km/s, B<10 nT, ǀBnǀ<2 nT. Under quiet solar wind conditions (V<450 km/s, B<5.5 nT, ǀBnǀ<0.7 nT), the degree of symmetry of the ring current increases. It is established that with intensification of interplanetary parameters (V, B, ǀBnǀ) the symmetric ring current index SYM-H grows more strongly than the asymmetric ring current index ASY-H.