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.

In this paper, we present the results of two series of experiments on radio sounding of near-solar plasma by the signals of the Mars Express and Venus Express spacecraft in 2006 and Mars Express in 2008. The radio sounding data are compared with measurements of the proton concentration near the Earth's orbit on the Wind satellite. This analysis shows that the general nature of the temporal dynamics of disturbances observed in two series of measurements is qualitatively similar. The sequence of amplifications of fluctuations in the frequency and density of protons indicates that the observed disturbances are associated with co-rotating regions of interaction of solar wind flows of various velocities.

The effect of interplanetary plasma on pulsed pulsar radiation passing through is considered. The pulses of two rotating radio transients (J0609+16, J1132+25) and a pulsar (B0320+39) detected on the Large Phased Array (Pushchino observatory) were analyzed. It is shown that in observations at the frequency of 111 MHz, on elongations of 20o-40o, both an increase and a decrease in the number of received pulses are observed. The change in the number of pulses is explained by the distortion of the energy distribution of pulses due to interplanetary scintillation. These changes in the number of observed pulses are in qualitative agreement with the expected dependence of the scintillation index on the observed sources elongation. Analytical expressions are obtained that allow estimating the effective modulation index from observations of individual pulses for the power distribution of pulses by energy.

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.

The University of California, San Diego (UCSD) time-dependent three-dimensional (3-D) reconstruction technique provides volumetric maps of density, velocity, and solar surface extrapolated magnetic fields by iteratively fitting our kinematic 3-D model to interplanetary scintillation (IPS) observations. While we currently use data from the Institute for Space-Earth Environmental Research (ISEE), Japan, we have also integrated this system adding data from Worldwide IPS Stations (WIPSS) network groups to increase both spatial and temporal coverage when these data are available. Some of these stations, especially the LOw Frequency ARray (LOFAR), centered in the Netherlands, currently operate in “campaign” mode only during periods of interest when the Parker Solar Probe (PSP) makes close passes to the Sun. The UCSD 3-D iterative reconstruction technique is unique in its ability to yield a low-resolution seamless extension of density and velocity parameters measured in situ, going outward into the surrounding interplanetary medium at the resolution of the volumetric data. We here present analyses using archival data sets from both ISEE, LOFAR, and BSA3 (Pushchino, Russia), mostly during PSP close passes of the Sun. These analyses provide the location of all inner planets from Mercury to Mars, and the spacecraft PSP, BepiColombo, and Solar Orbiter in the 3-D reconstructed volumes and can show the heliospheric structures that reach them as in-situ predictions of the structures present and forecasts of these parameters in near real time compared with near-Earth data sets.

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.

The results of experiments on radio sounding of near the Sun plasma by the signals of the Mars Express Mars satellite are presented. In the region of heliocentric distances of the proximate point of the line of sight of 8–13 solar radii, frequency fluctuations of transmission radio signals were measured. During the experiments sharp increases in the variance of frequency fluctuations were recorded on both the eastern and western limbs. In measurements near the Earth’s orbit on the Wind spacecraft in adjacent periods with a delay of 5–17 days, increases in the proton concentration and magnetic field strength were recorded at 7–15 times the background values. A comparison between the data related to the inner and near-Earth solar wind indicates that the observed disturbances are associated with the same region of the solar corona rotating with the Sun.

The paper reports the results of observations of the interplanetary scintillation of a compact radio source 3С 48 at the descending phase 24 solar cycle. The observations were conducted using a BSA LPI radiotelescope at frequency of 111 MHz. A comparison was made between an index (level) of the scintillation and solar wind speed, which was computed by a width of the scintillation temporal spectra. Complete series of observations from 2015 to 2019 displays a weak declining dependence of the scintillation level on the solar wind speed; the correlation, however, is rather low (averages about –0.15) due to a significant scatter in the data. With averaging over one-year intervals, the correlation coefficient module increases almost up to 1 with scintillation index in the mean approximately inversely proportional to solar wind speed. The paper further elaborates on a possible relationship between a spatial-temporal structure of the scintillation level and mean plasma density of the solar wind.

The observational data on interplanetary scintillations, obtained at the Large Scanning Antenna radio telescope of the Lebedev Physical Institute before the onset and during the magnetic storm lasting for 33 h from February 26 to 28, 2023 are considered. The enhancement of observed scintillations has begun 11 h prior to the magnetic storm onset at the heliocentric distance of 0.8 astronomical units. The model calculations using two-dimensional dynamic maps of scintillations allowed us to estimate the coronal mass ejection speed. It is found that the magnetic storm was caused by coronal mass ejection after an M3.7 flare occurred 34.5 h prior to the magnetic storm onset. The propagation velocity of coronal mass ejection is estimated as 900 km/s. The magnetic storm onset was predicted with sufficient accuracy, ~0.5 h. In 23 h after the M3.7 flare, an M6.3 flare occurred in the same active region, after which, presumably, a new ejection occurred, whose arrival at the Earth continued the lasting magnetic storm.

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.

The results of the long-term (2015–2019) series of interplanetary scintillation observations carried out with the LPA LPI radio telescope at the frequency 111 MHz are presented. We analyzed the radial dependences of the relative level (index) of interplanetary scintillations of the radio source 3C 48, the line of sight to which during the year shifts from low to medium and high heliolatitudes. For all annual series, we showed that the radial dependence of the scintillation index turns out to be flatter than expected for the model of a spherically symmetric medium. The difference is explained by the latitudinal effect, considering the influence of the near-equatorial layer with an increased plasma density. Modeling the low-latitude layer shows that the layer thickness at the phase of the decline in solar activity is, on average, two times greater than near the activity minimum.

Pulses from 16 previously known rotating radio transients (RRAT) have been searched at the 110 MHz daily monitor program for 4 to 5.5 years by using the Large-Phased-Array (LPA) at Pushchino. The total number of pulses detected in such a long observation interval is only 90 pulses for RRAT J0640+07 or is as high as 10,751 pulses for RRAT J0302+22. The number and amplitude of pulses varies at a time-scales from six to twenty months for RRATs J1336+33, J1404+11, J1848+15, J2051+12, J2105+22, and the pulse number can increase by one or two orders of magnitude in active phases. The long-term trends are found for RRATs J0139+33 and J0302+22, showing a 2-3 times increase in detected pulse number over 1,959 days. Some RRATs show the annual variations on both pulse number and pulse amplitude. It is hard to explain all these variation time scales by refractive scintillation on the interstellar medium. The annual and semi-annual variations are likely caused by scintillations of the inhomogeneous interplanetary plasma. Our data show that the number of observational sessions with no pulse detection over the threshold decreases exponentially with the length of pulse silence.

According to the data on the 20–24 solar activity cycles, long-term variations in the annual average solar wind speed and interplanetary scintillation index are compared to Wolf number variations. It is shown that the scintillation parameters at mid- and high heliolatitudes exhibit a slow nonmonotonic trend with a characteristic scale of the order of the secular cycle. For long-term data series since 1610 to the present, the correlation of variations of Wolf numbers and air temperature anomalies is analyzed. The possible application of the results to the global climate problem is discussed.