Scientific achievements. Solar system
2025
A robust preprocessing pipeline for RATAN-600 solar radio observations data
The RatanSunPy package was developed—an open-source Python software library designed to access, visualize, and analyze multiband radio observations of the Sun taken with the RATAN-600 solar complex. The package provides a full set of data processing tools including direct access to raw data, key preprocessing steps such as calibration to the quiet-Sun level, and tools for analyzing solar activity. These include automatic detection of local sources, matching them with NOAA (National Oceanic and Atmospheric Administration) active regions, and subsequent determination of the parameters of local sources and active regions. RatanSunPy enables more efficient exploration of the fine structure and dynamics of the solar atmosphere contributing to solar physics research and improving space weather forecasting. RatanSunPy is the first software package for processing solar observations from RATAN-600. The significance of the work lies in the fact that the RatanSunPy package will simplify access to and processing of RATAN-600 solar data potentially increasing research productivity and efficiency. RatanSunPy can be used, with appropriate adaptation, for processing solar radio observations from other telescopes.
The work was supported by RFBR grant No. 24-21-00476.
Authors:
Kurochkin E.A., Shendrik A.V. (SPbU SAO RAS), Knyazeva I.S. (GAO RAS), Derkach D.A. (HSE University), Makarenko N.G. (GAO RAS).
Published:
Knyazeva I., Lysov I., Kurochkin E., Shendrik A., Derkach D., Makarenko N., RATANSunPy: A robust preprocessing pipeline for RATAN-600 solar radio observations data, Astronomy and computing, 2025, v. 51, DOI: 10.1016/j.ascom.2024.100918.
2024
Detection of Depression Effects in Radio Emission from the Solar Corona
Absorption in many fine structures in coronal plasma has been detected using radio observations. The data were obtained at RATAN-600 with a new spectral complex with a relative frequency resolution of 10−5 and a time resolution of 8 ms in the range of 1–3 GHz in the radio emission spectra of individual active regions (ARs), prominences, and filaments. Similar structures in the form of “coronal rain” are studied in optics in the X-ray and EUV lines at large telescopes with diameters of 1.6 m and 4.0 m; but for the first time, they were discovered in the spectra of the corona at radio waves. The spectra of the quiet Sun and active regions of NOAA 13507(8) were obtained. New spectral capabilities of the instrument for studying the fine structure of the corona can be used to solve the problem of heating the solar corona and to measure its temperature balance.
Authors:
Bogod V.M., Lebedev M.K., Ovchinnikova N.E., Ripak A.M., Storozhenko A.A., Kurochkin E.A. (SAO RAS).
Published:
1. Bogod V.M., Lebedev M.K., Ovchinnikova N.E. et al. On a new concept of spectral radiometry at RATAN-600 // Izvestiya Krymskoy Astrophysical Obs. 2023. Vol. 119. No. 4. P. 17–26.
2. Ovchinnikova N., Bogod V., Lebedev M., Observation at radio frequencies of the hydroxyl (OH) absorption line in filaments and prominences above active regions of the Sun, Solar-Terrestrial Physics, vol. 10, issue 3, pp. 18-24, DOI:10.12737/stp-103202403.
Details
2023
1.3.7.4. Sun and near-Earth space, solar-terrestrial connections
1.3.7.6. Development of methods of ground-based and extra-atmospheric astronomy
Section 3. Sun; Section 11. Radio telescopes and methods
Detection of the hydroxyl (OH) absorption line in the radio emission of the solar corona
When observing the Sun with the RATAN-600 using a new high-speed spectral polarimetric complex with a frequency resolution of 0.12–8 MHz and a time resolution of 8 ms in the range of 1–3 GHz in the radio emission spectra of individual active regions (AR), an absorption line was discovered on the Sun in the frequency range of 1.5–1.65 GHz near the hydroxyl absorption line (1.7 GHz). The absorption was observed only in the emission of those ARs that were overlapped with a cool filament visible in the H-α images or on the limb in the presence of a prominence, where the existence of a hydroxyl molecule is potentially possible. The line shape corresponds to the estimated model calculations for conditions in a cool filament in the solar corona (7500 K, ~10-6 atm) taking into account the instrumental function of the 1–3 GHz spectral polarimetric complex (without taking into account the displacement due to a magnetic field). The discovery of molecular lines in the solar corona may indicate the nature of its heating and the stability of its temperature balance.
Authors:
Ovchinnikova N.E., Bogod V.M., Lebedev M.K., Ripak A.M., Storozhenko A.A., Kurochkin E.A. (SAO RAS).
Published:
1. Bogod V.M., Lebedev M.K., Ovchinnikova N.E., Ripak A.M., Storozhenko A.A., Spectroradiometry of the Solar Corona on the RATAN-600, Cosmic Research, 2023, Vol. 61, No. 1, pp. 27–33, DOI: 10.1134/S001095252301001X.
2. Ovchinnikova N.E., Lebedev M.K., Bogod V.M., Ripak A.M., A.A. Storozhenko, Results of a new approach to the analysis of multi-wavelength observations data obtained with RATAN-600 The Multifaceted Universe: Theory and Observations – 2022, 23-27 May 2022, SAO RAS, Nizhny Arkhyz, Russia; published December 14, 2022. Online at https://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=425, id.7.
3. Bogod V., Lebedev M., Ovchinnikova N., Ripak A., Kurochkin E., Detection of absorption in the decimeter radio emission of solar corona, The Multifaceted Universe: Theory and Observations – 2022, 23-27 May 2022, SAO RAS, Nizhny Arkhyz, Russia; published December 14, 2022. Online at https://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=425, id.5.
Details
2021
The effect of a magnetic field on the damping of slow magnetosonic waves in the solar corona
The influence of the magnetic field strength and the associated plasma parameter β (beta) on the dynamics of slow magnetosonic (MS) waves in plasma loops of the solar corona was studied. It has been demonstrated that the feedback effect of the thermal imbalance induced by MS waves with these waves makes it possible to explain the observed anomalously low Q factor of the waves of this type without involving anomalously high values of the thermal conductivity and viscosity coefficients. The results of this study are a theoretical basis for diagnosing key parameters of the Solar corona plasma, such as the magnetic field and the corona heating function by magnetohydrodynamic seismology using observations of solar and stellar flares both in the radio range, in particular with the RATAN-600 SAO RAS telescope after implementation of the guidance mode and with the help of SAO RAS optical telescopes. A separate significant result is the establishment of the application field of the infinite magnetic field approximation which greatly simplifies theoretical modeling of dynamic and thermal processes in plasma loops of the Solar corona.
Authors:
V.M. Nakariakov (SAO RAS) in cooperation with Duckenfield T.J. (the University of Warwick, Great Britain), Kolotkov D.Ju. (the University of Warwick, Great Britain; ISTP SB RAS).
Published:
Duckenfield T.J., Kolotkov D.Y., Nakariakov V.M., The effect of the magnetic field on the damping of slow waves in the solar corona, 2021, Astron. Astrophys., 646, A155, DOI:10.1051/0004-6361/202039791.
2018
Quasi-Periodic Pulsations (QPPs) in Solar Micro Flares
From polarized spectroscopic observations at RATAN-600 on January 25, 2017, we detected a strong “micro flare” with QPPs; it was unnoticed by the global solar monitoring stations working in various ranges. A characteristic feature of the spectrum lies in the fact that the gradual increase of flux with wavelength was followed by an abrupt explosive brightening in the range of 3-4 GHz tens times greater than the brightness of the quiescent Sun. Studies of the time evolution and comparison with EUV (extreme UV) showed that this type-B2 micro flare was initiated by the appearance of an S-like loop. The polarized radio emission from this micro flare observed at RATAN-600 was generated by non-thermal electrons, whose hard X ray emission was detected with the RHESSI space mission. The result is unique, as the limiting parameters combined the space and ground-based observation complexes and a rare flash event with a new radiation mechanism was detected.
Authors:
Nakariakov V.M. (SAO RAS, the University of Warwick, GB), Anfinogentov S. (ISTP SB RAS), Storozhenko A.A. (SAO RAS), Kurochkin E.A. (SAO RAS), Bogod V.M. (SAO RAS), Sharykin I.N. (OFMZ SB RAS, IKI RAS), Kaltman T.I. (SAO RAS).
Published:
1. Nakariakov, V.M., Anfinogentov, S., Storozhenko, A.A., Kurochkin, E.A., Bogod, V.M., Sharykin, I.N., Kaltman, T.I., Quasi-periodic pulsations in a solar microflare, Astrophys. J. 859, 154, 2018.
2. V.M. Bogod, T.I. Kaltman, A.A. Pervakov, Yu.V. Sotnikova, S.A. Trushkin (SAO RAS, Russia) Solar powerful short-term flare in NOAA12628 at 3-4 GHz on 25 Jan 2017, 10:16:43 UT ATel #10011; on 27 Jan 2017; 13:32 UT.
2017
Detection of the 4th harmonica in the cyclotron radiation above the spot
Radiation of the 4th harmonica of the gyro-frequency in the Solar corona above the spot was detected due to detailed spectroscopic observations at RATAN-600 with high accuracy polarization measurements. Radio astronomical measurements of cyclotron radiation are based on the fact that radiation generated in a magnetic field is circularly polarized, and the sign and degree of polarization depend on the type of radiation mechanism, temperature, and density of plasma, in the place where the radiation emerged and propagated. In the case of the defined emission mechanism, polarization measurements of radio emission provide an opportunity to determine the magnetic field strength. Significance of the result obtained is defined by the importance of measurements of coronal magnetic fields in those areas of the solar atmosphere, where traditional optical methods based on the Zeeman and Hanle effects are inefficient because of high coronal temperatures.
Authors:
Kaltman T.I., Bogod V.M., Storozhenko A.A.
Published:
The result was presented at the “Solar and Solar-Terrestrial Physics 2017” XXI Russian Annual Conference on Solar Physics (October 9, 2017 — October 13, 2017), Pulkovo Observatory.
2016
Estimation of efficiency of radio astronomical forecast on the flare activity
The authors estimated the efficiency of a prediction on flare activity in active regions based on spectropolarization observations at RATAN-600 in the wide radio-wave range. The method is aimed at a short-term flare forecast (1-3 days). Preparation of a reliable forecast is a complex process due to multi-parametric description of plasma and many nonlinear relationships between parameters. The authors used radio astronomical forecast method for an active event by analyzing the intensity spectrum and polarization of radiation in an active region. The calculated efficiency of the forecast of proton flares is 94% with a 13.2% error, the efficiency of the forecast of strong flares is 88% with a 12.8% error.
Authors:
Bogod V.M., Kurochkin E.A., Peterova N.G., Shendrik A.V. (SAO RAS), Svidskii P.M. (IPG Goskomgidromet), Everstov N.P. (ITMO University).
Published:
Bogod V.M., Svidskii P.M., Kurochkin E.A., Peterova N.G., Shendrik A.V., Everstov N.P. On the method of solar activity forecasting based on radio observations. Abstracts of the XX “Solar and Solar-Terrestrial Physics-2016” conference, St. Petersburg, October 2016 (the paper is submitted to the “Geomagnetism and Aeronomy” journal).
Reconstruction of the atmosphere of the Solar corona over a spot using recent data
We obtained first results of measurements of temperature above active regions using the automatic iteration method of radio emission estimation applied to the observed results from RATAN-600 in the range of 2-18 GHz at several dozen wavelengths. The method was used for some active regions and, as a result, we experimentally and efficiently measured the increasing temperature in the Solar transition region and lower corona over single spots. We have detected the increase in temperature in the transition region and lower corona which generally conforms to the adopted Selhorst model taking into account individual features of active regions. The results are in good agreement with direct measurements of a magnetic field at the base of the corona from radio observations and allow one to refine a height estimate for these measurements.
Authors:
Kaltman T.I., Bogod V.M., (SAO RAS), Stupishin A.G., Yasnov L.V. (Saint Petersburg State University).
Published:
Stupishin A., Bogod V., Kaltman T., Yasnov L., Modeling of solar atmosphere parameters above the active region using RATAN-600 radiotelescope observation, Programme and abstracts of CESRA 2016: Solar Radio Physics from the Chromosphere to Near Earth June 13-17 June 2016, Orleans (France), electronic issue, p. 100.
2012
Discovery of the generation of high-energy electrons in a weak flare
Sub-second pulses were recorded for the first time at RATAN-600 with a temporal resolution of 7 ms in the range from 3.5 to 8 GHz, which is confirmed by independent observations on the Siberian Solar spectropolarimeter in the 4-8 GHz range. These pulses emerge in the impulsive phase of the flare and are superimposed on the flares of longer duration. A comparison of the temporal profiles and spectra for the microwave and hard x-ray emission (HESSI and FERMI data), as well as the simulations of gyrosynchrotron emission, show that the nature of these sub-second oscillations in weak flares is determined by a common population of electrons and a common high-temperature source of emission with the temperature greater than 30 MK.
In collaboration with the Institute of Solar-Terrestrial Physics of the Siberian branch of RAS.
(Contact — V.M. Bogod).
2011
A comparison of radiation in the corona above the spot in the radio and X-ray ranges
In the observations of the 04.01.2011 solar eclipse at the RT-32 (the observatories Svetloe and Zelenchukskaya) and RATAN-600 radio telescopes the limiting angular resolution (1 arc second) in the eclipse observations in the microwave frequency range was reached for the first time, determined by the diffraction on the lunar limb. We obtained accurate measurements of the effective height above the photosphere, where in the corona the source of microwave radiation over the spots is located. The positions of the spot center in the radio range with the images in the coronal lines of the ultraviolet and X-ray ranges were compared. It was found that the measured high brightness temperature of the radio source above the spot, amounting to 6 million degrees, does not yield any luminance in the coronal lines. This indicates a different nature of plasma heating in the radio, EUV and X-ray frequency ranges.
(Contact — N.G. Peterova).
2010
Sources of polarized radiation with unusual spectral features discovered in the Sun
In the framework of the study of solar active regions that produce powerful flares the researchers from the RATAN-600 radio telescope have detected sources with features in the form of a sharp decrease in the intensity of polarized radiation in various parts of the recorded frequency range (2-16 GHz), sometimes changing the sign of polarization. Modeling of the phenomenon indicates the presence of a hot coronal loop at the heights of about 10 Mm (the height of the transition region is about 2-5 Mm). The magnetic field strength of the hot region was measured at 360-450 gauss.
In collaboration with St. Petersburg State University.
(Contact — V.M. Bogod).
2009
Height Structures of Magnetic Fields in Solar Active Regions
The methods of multiwavelength radio astronomy have shown that over the solar spots the magnetic fields with the strength of approximately 1000 G are measured at rather large heights in the solar atmosphere (from 10 to 25 thousand km), which is confirmed by the space observatory observations in the ultraviolet lines of magnetic loops. These data contradict the conventional models of the magnetic field; hence we have to use the models for a very structured and twisted vertical magnetic field over the spot.
In collaboration with SPBU.
(Contact — V.M. Bogod).
2008
Spiral structure of the magnetic field in AO 0953 over a stable spot.
A two-dimensional high-altitude structure of the coronal magnetic field, with the power tube extending up the ~0.4°-wide spiral was observed over a stable spot in the active region AO 0953. The magnetic field of around 600 Gs is located at a rather high altitude in the solar corona (up to 25 thousand km). Radio astronomical multifrequency polarization observations of sources with the RATAN-600 were used.
In collaboration with St. Petersburg University.
(Contact — V.M. Bogod).
2006
As a result of observations of a total solar eclipse on the RATAN-600 in the microwave range we have carried out:
1) A study of the solar corona. Owing to the large effective area of the radio telescope and an absence of scattered background, high accuracy radiometry measurements of radial brightness distribution of a weak radiation behind the limb were carried out for the first time, and the data on the corona density at the distances of up to one solar radius in the range of brightness temperatures of 100 – 1 K were obtained.
2) The study of the solar northern polar region. A powerful radio source above the solar North Pole in the region of the polar coronal hole was discovered. Its contrast sharply increases toward shorter wavelengths and is dominant at the wavelengths of ~ 2.0 cm. The source intensity amounts to ~1.5% of the quiet Sun. Its fine spatial structure with fluctuations at the level of 0.06% was discovered. A transition boundary from brightening to darkening at the wavelength of 3.5 cm was found in the emission of the polar coronal hole. These facts are decisive for the choice of the solar cycle model.
3) Polarized radio emission of a high-latitude prominence was registered. This emission occurs at the boundary between the transition zone from the cold mass of the prominence and the surrounding corona. The magnetic field of the prominence was measured and a complex sign-alternating structure of its longitudinal component with unexpectedly high peak values (300-700 F) was discovered.
2003
From RATAN-600 observations with a matrix radiometer at a wavelength of 1 cm indications have been found of existence of relativistic electrons in the magnetosphere of Jupiter with energy of about 100 MeV, which demands revision of mechanisms of acceleration of cosmic rays of the solar wind with energy of a few MeV. The longitudinal distribution of radio brightness over the disk of the planet, which is much more homogeneous in comparison with latitudinal, has been obtained for the first time.
Based on a new method of multiazimuthal observations at RATAN-600 in the decimeter range direct evidence of existence of long-duration non-thermal radiation in the magnetosphere of the solar active region (halo) has been found and plasma mechanisms explaining their nature have been suggested.
In co-operation with SPbSU and Beijing Observatory (China).
Details (PDF)
2002
According to the RATAN-600 observations of the Sun in the microwave range, we isolated a class of flare-productive active regions, characterized by abrupt reversals of circular polarization in frequency and time in the interval from several hours to three days. This indicates the existence of a long preparatory phase in the preflare solar radiation. Such an early registration of the preflare status opens up opportunities for developing new methods for forecasting powerful proton events on the Sun.
2001
New manifestations of solar activity, which allow predicting the proton flares on the Sun, were detected during the observations with the RATAN-600. Preflare plasma revealed sources with a large slope of the spectrum and repeated inversion of the polarization sign in the radio wave range of 2-5 cm. The effect of darkening of microwave radiation in individual active regions was as well detected.
2000
It is shown that radio emission of microbursts in solar active regions is the manifestation of noise storms at the fundamental plasma frequency, and is the result of instabilities propagating at the tops of coronal loops. Noise storms are perceived as large-scale active formations, covering the layers of the solar atmosphere from the tens to hundred thousand kilometers above the photosphere.
Collaboration with the Nancay Decimetric Radio Telescope (France).
A method for determining the height of the corona base above sunspots was proposed. The technique is based on the comparison of radio astronomical and magnetographic observations on the RATAN-600, the values of which are enclosed in the range of 500 and 4500 km. The magnetic field, determined from the third harmonic of the gyrofrequency, reaches its maximum value at the base of the solar corona and is at odds with the value, determined from the second harmonic, which is inconsistent with theoretical expectations.
1999
According to observations of solar radio emission at the RATAN-600 with record-high sensitivity in the decimeter wave band a new type of pulsed sources was detected, indicating a long-term release of nonthermal energy in active regions.
1998
The RATAN-600 observations of solar active regions:
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experimental evidence was found of the existence of cyclotron emission lines, earlier predicted by Zheleznyakov V.V. and Zlotnik E.Y.; the line detected was located in a bright source of thermal nature and had an emission band of 10-12% at the wavelength of 8.5 cm, the brightness temperature of 107 K;
(Collaboration with the IAP RAS). -
direct measurements of the magnetic field in the coronal hole at the bottom of the corona were performed, the magnetic field strength (the calculations were carried out as part of the thermal bremsstrahlung mechanism of radio emission generation of the solar plasma in the weak magnetic field) increases from the values of 0.2 G at the photosphere level up to 7-10 G at the level of radio emission formation at the wavelength of 18 cm and is then remains unchanged (or decreases slightly) down to the level of radio emission formation at the wavelength of 30 cm.
(Collaboration with MAO RAS).
1997
As a result of comprehensive RATAN-600 studies of the prominence on the W limb of the Sun, its instant detailed radiation spectrum in the range from 1.7 to 32 cm (at 39 different wavelengths) was obtained for the first time. We observed its multi-component structure and detected the source of increased heating at the prominence-corona boundary.
Own radio emission from the lunar crater Copernicus was registered for the first time at 1.38 and 2.7 cm wavelengths in the RATAN-600 observations of the Moon. This indicates a temperature increase in this crater up to 100 K at the depth of 5 m.
1996
Using the original method of diagnostics of the Solar corona structure by the effects of radio wave refraction (space-frequency tomography) in the wavelength range of 2-30 cm on the RATAN-600 telescope, the electron density, emission measure and porosity of coronal loops was measured for the first time regardless of the optical data. It is shown that most of the matter is concentrated in the super-dense loops, occupying less than 10% of the total coronal volume.
Comparing the data of microwave and VHF radio emission with the new RATAN-600 data on the inversion of polarization it was found that the narrow-band dual polarization inversion is observed in active regions with noise storms. This phenomenon is interpreted as an indication that the current layers are located in the upper solar corona, being the sources of particle acceleration and energy storing places for the noise storms.
1994
As a result of comparing the spectra of active solar regions from the observations with high spatial resolution in the microwave range at the RATAN-600 (the S-component) with a flare component observed at meter wavelengths on the VLA (USA) we revealed the presence of a strong and prolonged noise storm exactly where a weak decaying active region (with the presence of powerful active regions in the disk) is located. The data obtained indicate a direct relationship between the so-called UHF halo, earlier detected with the RATAN-600 and nonthermal radiation of noise storm sources, existing for a long time.
In July 1994, complex studies of the effects of impact of the Shoemaker-Levy 9 comet on Jupiter were made.
With the aid of spectral observations of the impact regions of W and K comet fragments, made in the range of 4 microns at the BTA with the use of a Fourier spectrometer, smoke was detected that arose in the stratosphere at the altitudes, corresponding to pressures from 5 to 50 mbar. The Albedo of a slowly evolving thin cloud, resulting from the collision, is equal to 0.13-0.15. Spectral observations of a unique event in the range of 4-10 microns were performed only at the 6-m telescope.
(In collaboration with the Paris Observatory, France; the Institute for Space Aeronomy, Belgium; and IKI RAS).
Based on the RATAN-600 observations conducted during the fall of comet fragments, a 10-20% increase of the radiation intensity of Jupiter at the wavelengths of 7.6, 13, 18 and 31 cm was detected. A perturbed radiation state of Jupiter's radiation belts (they are responsible for emission in the decimeter band) persisted for at least a week after the infall of the last fragments. At 3.10 m wavelength within 3-5 minutes after the fall of the cometary fragments bursts of radio emission were detected, and the parameters of ionospheric disturbances were measured.
1993
Based on the microwave observations of the Sun on the RATAN-600 and the Large Pulkovo Radio Telescope with high spatial and frequency resolution a new model of interaction of the photospheric and coronal magnetic fields in active regions was finalized. The model of the magnetosphere of the active region is represented as a space in the solar atmosphere, where the plasma parameters, its structure, magnetic field value, the energy release processes are defined and regulated by the interaction of the coronal plasma with magnetic fields, which are a continuation of photospheric magnetic fields of the active region.
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