Solar wind diamagnetic structures as a source of substorm-like disturbances

Abstract

The purpose of this study is to generalize the results of investigation of the magnetosphere response to two types of diamagnetic structures. Type 1 is related to sporadic SW, type 2 - to the quasi-stationary “slow” solar wind (SW). First, we consider the Type 1 of diamagnetic structures that are connected with sporadic SW, whose source on the Sun is coronal mass ejections (СМЕs). Near the rear side of a magnetic cloud, one often observes a thin magnetic rope with a high-density plasma. This rope is ejected by a filament (or an eruptive prominence) from the solar surface. The rope is a diamagnetic structure with the same properties, as those of a magnetic tube. Such tubes are diamagnetic, i.e., a diamagnetic current flows on their surface. This current decreases the magnetic field inside the pipe and increases the latter outside. The total pressure (magnetic plus gas-kinetic) is approximately constant inside and outside the tube. Tubes keep their angular size during propagation from the Sun to the Earth, i.e., they are quasi-static. Type 2 represents magnetic tubes (in general case, magnetic ropes) whose sources on the Sun are the streamer belt and the streamer chains or pseudo-streamers. In the Earth orbit, the SW diamagnetic structures are detected by the presence of anti-correlation between the SW proton density and the magnitude of interplanetary magnetic field (IMF). The analysis showed that an interaction of diamagnetic structures (DSs) with the Earth magnetosphere generates substorm-like (sawtooth) magnetic disturbances in the nightside magnetosphere. The disturbances are different from classical substorms because of the absence of the growth phase and of the breakup. The diamagnetic structures related to the quasi-stationary slow SW cause a global modulation of the magnetic activity and of the ionospheric currents with a period close to the period of the variations in the SW plasma density and in the IMF strength inside the diamagnetic structure.