Corotating and Propagating Disturbances in the Solar Wind Based on Monitoring of Interplanetary Scintillations at the LPA Radio Telescope of the Lebedev Physical Institute in 2017

Monitoring of interplanetary scintillations in 2017 is used as a basis for analyzing the dynamics of scintillation levels in periods preceding the arrival at the Earth of eight large-scale disturbances in the solar wind giving rise to strong geomagnetic storms. In six of the eight events, the dynamics of the scintillation level were mainly determined by the motion of corotating disturbances. In two events, coronal-mass ejections excited in the corona near the western limb of the Sun were observed against the background of corotating disturbances. In one of these cases, a magnetic storm was associated with a corotating flux, and in the other with a powerful propagating disturbance. Comparison with similar data obtained in 2016, also during the descending phase in solar activity, testifies to the existence of corotating disturbances with lifetimes of at least 20 solar rotations. These new results support the earlier conclusion that a weakening of scintillations is observed in the evening sector three to four days before the arrival of the compressed part of a disturbance to the Earth, which could be due to an appreciable lowering of the level of small-scale turbulence in the plasma in an extended region ahead of the frontal part of the disturbance. The interplanetary-scintillation monitoring data for 2017 show that, simultaneously with the associated magnetic storm, there is an enhancement of second-time-scale scintillations, which are most clearly manifest when the storm occurs during the evening or night-time hours. For the events considered, the increase in scintillations accompanying the magnetic storm is associated with an enhancement in the level of small-scale fluctuations in regions of the solar wind adjacent to the Earth when the storm is excited by a corotating disturbance, and with the perturbed ionosphere when the storm is excited by a flare-related disturbance.