Observations of Corotating Streams of the Solar Wind with the Large Phased Array of the Lebedev Physical Institute in 2016

Abstract

Solar and geomagnetic data demonstrate that, at the decay phase of solar activity in 2016, the dominating role in strong geomagnetic perturations was played by long-lived corotating regions of interaction between solar-wind streams with different velocities. The results of monitoring of interplanetary scintillations in time intervals preceding the arrival to the Earth of several corotating solar-wind perturbations observed in 2016 have been analyzed. The aim of the study is to determine the characteristic features of the dynamics of the scintillation level. The scintillations in the twilight sector weaken three to four days before the arrival of the compressed part of the perturbation at the Earth, which can be interpreted as a considerable decrease in the level of small-scale plasma turbulence in the extended region upstream of the frontal part of the perturbation. The arrival of the perturbation at the Earth is not always accompanied by a magnetic storm. Confident short-term geomagnetic activity forecasting requires additional data about the direction of the B_z magnetic field component in the perturbed stream. Monitoring of interplanetary scintillations shows that, simultaneous with the magnetic storm, second-timescale scintillations are enhanced, which are recorded most clearly if the storm takes place during twilight or night-time hours. In contrast to flare-driven perturbations, when the enhancement of night-time scintillations is due to the perturbed ionosphere, in the case of corotating perturbations, the accompanying scintillation enhancement is related to the interplanetary medium adjacent to the Earth, and is due to an increase in the absolute level of small-scale turbulence in the compressed part of the perturbation.