The search for long-term variability of compact components of radio sources B0821+394 and B1812+412 over an interval of ten years was carried out. The LPA LPI radio telescope with an operating frequency of 111 MHz was used for observations. According to our estimates, the characteristic time of variability for both sources is 1.5–2.5 years. It is shown that the observed variability is not related to intrinsic variations in the radiation flux, but is due to refractive scintillation on inhomogeneities of the interstellar medium. From the obtained upper estimates of the apparent angular dimensions of the sources, it follows that the main contribution to the scattering of radio emission is made by turbulent plasma concentrated in sufficiently thin screens, the distance to which does not exceed 300–400 pc.

The results of the analysis of interplanetary scintillation observation data obtained by the radio telescope Big Scanning Antenna of the Lebedev Physical Institute (BSA LPI) before, during and after the magnetic storm that occurred on December 1–2, 2023, are presented. The observational data are compared with model calculations for corotating and propagating large-scale disturbances. The results of observations of scintillating radio sources indicate that the magnetic storm that took place was caused by a superposition of two types of large-scale solar wind disturbances. On the day before the start of the magnetic storm, signs of interaction between the Earth’s magnetosphere and the corotating region of multi-velocity solar wind flows were observed, whereas later signs of magnetosphere disturbance by coronal mass ejection spreading after the M9.8 solar flare on November 28, 2023, were observed.

The results of the analysis of observational data of interplanetary scintillations obtained at the Big Synphasic Antenna radio telescope of the Lebedev Physical Institute (BSA LPI) before, during and after the magnetic storm that occurred on December 1–2, 2023. Observational data were compared with model calculations for corotating and propagating large-scale disturbances. The results of observations of scintillations of radio sources indicate that the magnetic storm that took place was caused by the superposition of two types of large-scale disturbances of the solar wind. On the day before the start of the magnetic storm, signs of interaction of the Earth’s magnetosphere with the corotating region of multi-velocity solar wind flows were observed, whereas later signs of disturbance of the magnetosphere by a coronal mass ejection propagating after the M9.8 flare on November 28, 2023 were observed.

The search for long-term variability of compact components of radio sources B0821+394 and B1812+412 over an interval of 10 years was carried out. The LPA LPI radio telescope with an operating frequency of 111 MHz was used for observations. According to our estimates, the characteristic time of variability for both sources is 1.5–2.5 years. It is shown that the observed variability is not related to intrinsic variations in the radiation flux, but is due to refractive scintillation on inhomogeneities of the interstellar medium. From the obtained upper estimates of the apparent angular dimensions of the sources, it follows that the main contribution to the scattering of radio emission is made by turbulent plasma concentrated in sufficiently thin screens, the distance to which does not exceed 300–400 pc.

IPS monitoring observations with the radio telescope BSA LPI are described. We summarize briefly the previous results of prior IPS observations. We show that IPS enhancements associated with ICMEs take place after coronal flares at a time that is on average about half the time needed for a disturbance to reach the Earth. Decreases in night IPS level caused by CIRs are observed for 2-3 days before geomagnetic storms. The recent data are presented for an ICME and a geomagnetic storm in early November 2021. The start of the IPS increase was observed at an elongation of about 45 degrees, 27.5 hrs after the coronal flare and 14.5 hrs before the geomagnetic storm. (c) 2022 COSPAR. Published by Elsevier B.V. All rights reserved.

From April 2021 to October 2022, in the monitoring data obtained daily at the Big Scanning Antenna radio telescope (BSA LPI), 11 events were identified for which X-ray flares in the solar corona were followed by magnetic storms on Earth. Interplanetary scintillation monitoring data were considered together with data on solar flare activity and a simple kinematic model of ejection propagation. Based on the estimated ejection velocity between the Sun and the probed region, under the assumption of a constant velocity, the time of arrival of the ejection to the Earth was calculated. Of the 11 events considered, 7 are associated with solitary flares followed by a coronal mass ejection (CME) and 4 are more complex and possibly associated with corotating perturbations or a superposition of corotating and flare perturbations. For the entire set of events, the average time of the real onset of a magnetic storm after the time predicted by the model was 3.6 h and the average time between the onset of scintillation enhancement and the onset of a magnetic storm was 20.1 h. For events associated with solitary flares, the magnetic storm began, on average, 0.8 hours after the predicted time and 15.6 hours after the onset of scintillation enhancement. The delay of magnetic storms with respect to the predicted time is apparently related to the deceleration of the ejection between the probed region of the solar wind and the Earth's orbit.

A simple model has been proposed for the leading part of an interaction region between solar wind streams of different speeds. The model describes an increased plasma concentration as a spiral jet with a rectangular cross-section. Using this model, two-dimensional dynamic maps of interplanetary scintillation level distribution were calculated, which were specifically adapted to the configuration of the BSA LPI radio telescope. The model calculations were compared with the data from a series of observations of interplanetary scintillation during four geomagnetic storms in 2022 and 2023, caused by corotating disturbances. The calculations and observational data exhibit a qualitative correspondence. It has been shown that corotating disturbances manifest as scintillation enhancement three days before a geomagnetic storm, occurring at around 15:00–16:00 Moscow time. Over the next two days, the scintillation enhancement zone shifts to a later time, while there is no enhancement in the morning sector. During the actual geomagnetic storm period, there is an increase in night scintillations. This sequence of scintillation enhancement indicates that the disturbance approaches Earth from the eastern side while rotating with the Sun. The qualitative differences between the observational data for corotating and propagating large-scale disturbances are discussed.

A comparison is made of the data from the annual series of interplanetary scintillation monitoring performed at the maximum (2015) and minimum (2019) of solar activity. The observations were carried out with the LPA LPI radio telescope at the frequency 111 MHz. We showed that the time-of-day dependences of the scintillation level averaged over monthly intervals for the summer months at the minimum and maximum are approximately the same. For the winter months, at the decay phase and at the minimum of activity, an annual periodicity in the scintillation level is observed; at the maximum of activity, there is no periodicity. The results obtained can be explained by a combination of the cyclic dynamics of the global structure of the solar wind and the change in the location of the solar wind regions probed in the experiment during the year.

By the example of two events of 2016, changes in the interplanetary scintillation level during corotating solar wind disturbances causing geomagnetic storms are analyzed. It is shown that night scintillations are attenuated before dense disturbance part arrival at the Earth, which is followed by a significant increase during the magnetic storm and a day after it. For interplanetary scintillations in the morning sector, such changes are absent: the scintillation level remains approximately constant. A comparison with the WIND satellite data shows that changes in night scintillations and the average plasma concentration near the Earth’s orbit occur qualitatively in a similar way.

The search for compact components of strong ($${{S}_{{{\text{int}}}}} \geqslant 5$$ Jy at 102.5 MHz) discrete radio sources from the Pushchino catalogue was carried out using the method of interplanetary scintillation. A total of 3620 sources were examined, and 812 of them were found to harbor compact (scintillating) components. Estimates of fluctuations of the flux density of these compact components were derived from the scintillation index ($${{m}_{{\max}}}$$) corresponding to an elongation of 25°. The angular size and compactness of 178 sources with compact components were estimated. Scintillation indices of sources corresponding to the compact component ($${{m}_{0}}$$) and flux densities of compact components were determined. It was demonstrated that slow variations of the spatial distribution of interplanetary plasma, which are related to the 11-year cycle of solar activity, may exert a systematic influence on the estimates of angular sizes of sources. Coefficients compensating the deviation from the spherical symmetry of solar wind in the estimates of angular sizes were found using the coefficient of asymmetry of the statistical distribution of intensity fluctuations. The study of correlations between the parameters of sources in the sample revealed that the maximum value of the scintillation index decreases as the integrated flux increases, while the angular size has no marked dependence on the integrated flux.

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.

An analysis of data from three years of monitoring of interplanetary scintillations in 2015–2017 during a phase of decreasing solar activity is presented. The observations were carried out on the Large Scanning Antenna of the Lebedev Physical Institute at 111 MHz. During the period considered, the spatial distriution of the scintillation level was close to spherically symmetrical, on average, and did not undergo any strong time variations on scales of months or years. The monthly-mean scintillation level is not correlated with theWolf number.

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 Bz 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.