Geoeffective Disturbances in the Solar Wind near the Solar Activity Minimum according to the Data of a Two-year Series of Observations of Interplanetary Scintillations with the BSA LPI Radio Telescope.

A joint analysis of the monitoring data of interplanetary scintillations with solar and geophysical data showed that at the descending phase of the 24 solar activity cycle, the dominant role in geomagnetic disturbances, is associated with corotating disturbances in the solar wind. In 2018–2019, when approaching a deep minimum of activity, 12 of 13 strong magnetic storms were caused by the arrival of a compressed part of the interaction regions of flows of different velocities to the Earth. Only in one event, on May 11, 2019, the superposition of flare disturbances with the corotating one was observed. Comparison with the results of similar data in 2016 and 2017 shows the existence of corotating disturbances with a lifetime of at least several solar rotation. The conclusion is confirmed that 3–4 days before the compressed part of the perturbation arrives at the Earth, the evening and night scintillations begin to weaken, which can be interpreted as a significant decrease in the level of small-scale plasma turbulence in the extended region ahead of the perturbation frontal part. The weakening of the second scintillations in the evening sector with a duration of 2–3 days can be -considered as a precursor to the approach of a corotating perturbation to the Earth. As in 2016–2017, simultaneously with the magnetic storm, an intensification of the second's scintillations occurs, which is most clearly recorded if the storm occurs in the evening or at night. [ABSTRACT FROM AUTHOR]