The article discusses characteristics, fundamental and applied tasks of the Siberian Radioheliograph that is developed at the ISTP SB RAS Radio Astrophysical Observatory and spectropolarimetric complex that measures the total flux of solar radio emission. The multi-wave mapping of the Sun in the microwave range is a powerful and relatively inexpensive, in comparison with space technologies, means of observing solar activity processes and diagnosing plasma parameters. All-weather monitoring of electromagnetic solar emission (in the range from meter to millimeter waves, including measurements of the solar activity index at 2.8 GHz), and at the location of other diverse diagnostic facilities of the Heliogeophysical Complex, is of particular value. Radioheliograph data is necessary to develop and implement methods of short-term forecast of solar flares, measurements of kinematics and characteristics of coronal mass ejection plasma, forecast of characteristics of fast solar wind streams.

Small-scale ionospheric irregularities affect navigation and radio telecommunications. We studied small-scale irregularities observed during the 22 June 2015 geomagnetic storm and used experimental facilities at the Institute of Solar-Terrestrial Physics of the Siberian Branch of the Russian Academy of Sciences (ISTP SB RAS) located near Irkutsk, Russia (~52°N, 104°E). The facilities used were the DPS-4 ionosonde (spread-F width), receivers of the Irkutsk Incoherent Scatter Radar (Cygnus A signal amplitude scintillations), and GPS/GLONASS receivers (amplitude and phase scintillations), while 150 MHz Cygnus A signal recording provides a unique data set on ionosphere small-scale structure. We observed increased spread-F, Cygnus A signal amplitude scintillations, and GPS phase scintillations near 20 UT on 22 June 2015 at mid-latitudes. GPS/GLONASS amplitude scintillations were at a quiet time level. By using global total electron content (TEC) maps, we conclude that small-scale irregularities are most likely caused by the auroral oval expansion. In the small-scale irregularity region, we recorded an increase in the precise point positioning (PPP) error. Even at mid-latitudes, the mean PPP error is at least five times that of the quiet level and reaches 0.5 m.

The article discusses characteristics, fundamental and applied tasks of the Siberian Radioheliograph that is developed at the ISTP SB RAS Radio Astrophysical Observatory and spectropolarimetric complex that measures the total flux of solar radio emission. The multi-wave mapping of the Sun in the microwave range is a powerful and relatively inexpensive, in comparison with space technologies, means of observing solar activity processes and diagnosing plasma parameters. All-weather monitoring of electromagnetic solar emission (in the range from meter to millimeter waves, including measurements of the solar activity index at 2.8 GHz), and at the location of other diverse diagnostic facilities of the Heliogeophysical Complex, is of particular value. Radioheliograph data is necessary to develop and implement methods of short-term forecast of solar flares, measurements of kinematics and characteristics of coronal mass ejection plasma, forecast of characteristics of fast solar wind streams.

The Irkutsk Incoherent Scatter Radar (IISR) allows us to carry out passive radio observations of the Sun and other powerful radio sources. We describe a method for absolute measurements of spectral flux density of solar radiation at IISR. The absolute measurements are meant to determine the flux density in physical units [W·m–2·Hz–1]. The IISR antenna is a horn with frequency beam steering, therefore radio sources can be observed at different frequencies. Also there is a polarization filter in the antenna aperture, which passes only single (horizontal) polarization. To acquire flux density absolute values, the IISR receiver is calibrated by the Cygnus-A radiation. Since the Sun’s position in the IISR antenna pattern is determined by a frequency differing from the Cygnus-A observation frequency, we perform an additional calibration of the frequency response in the 154–162 MHz operation frequency range, using the background sky noise. The solar disk size is comparable with the main beam width in the north—south direction, hence the need to take into account the shape of the brightness distribution in the operation frequency range. The average flux density of the quiet-Sun radiation was ~5 sfu (solar flux units, 10–22 W·m–2·Hz–1) at the 161 MHz frequency.