Alexey A. Kuznetsov

Alexey A. Kuznetsov
Institute of Solar-Terrestrial Physics · Department of Radio Astrophysics

PhD

About

91
Publications
6,892
Reads
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1,375
Citations
Introduction
Alexey A. Kuznetsov currently works at the Department of Radio Astrophysics, Institute of Solar-Terrestrial Physics (Irkutsk, Russia). Alexey does research in Plasma Physics, Astronomy and Astrophysics.
Additional affiliations
December 2012 - present
Institute of Solar-Terrestrial Physics
Position
  • Principal Investigator
December 2009 - November 2012
Armagh Observatory
Position
  • PostDoc Position
September 2003 - November 2009

Publications

Publications (91)
Article
Full-text available
We present a database of solar flares registered by the Konus-Wind instrument during more than 27 yr of operation, from 1994 November to now (2022 June). The constantly updated database (hereafter KW-Sun) contains over 1000 events detected in the instrument’s triggered mode and is accessible online at http://www.ioffe.ru/LEA/kwsun/ . For each flare...
Preprint
Full-text available
We present a database of solar flares registered by the Konus-Wind instrument during more than 27 years of operation, from 1994 November to now (2022 June). The constantly updated database (hereafter KW-Sun) contains over 1000 events detected in the instrument's triggered mode and is accessible online at http://www.ioffe.ru/LEA/kwsun/. For each fla...
Article
Full-text available
The modulation of the microwave emission intensity from a flaring loop by a standing linear sausage fast magnetoacoustic wave is considered in terms of a straight plasma slab with the perpendicular Epstein profile of the plasma density, penetrated by a magnetic field. The emission is of the gyrosynchrotron (GS) nature, and is caused by mildly relat...
Preprint
Full-text available
The modulation of the microwave emission intensity from a flaring loop by a standing linear sausage fast magnetoacoustic wave is considered in terms of a straight plasma slab with the perpendicular Epstein profile of the plasma density, penetrated by a magnetic field. The emission is of the gyrosynchrotron (GS) nature, and is caused by mildly relat...
Article
Full-text available
We present the first multiwavelength simultaneous detection of quasi-periodic pulsations (QPPs) in a superflare (more than a thousand times stronger than known solar flares) on a cool star, in soft X-rays (SXRs, with XMM-Newton) and white light (WL, with Kepler). It allowed for the first ever analysis of oscillatory processes in a stellar flare sim...
Preprint
Full-text available
We present the first multi-wavelength simultaneous detection of QPP in a superflare (more than a thousand times stronger than known solar flares) on a cool star, in soft X-rays (SXR, with XMM-Newton) and white light (WL, with Kepler). It allowed for the first-ever analysis of oscillatory processes in a stellar flare simultaneously in thermal and no...
Article
Full-text available
The past decade has seen a dramatic increase in practical applications of microwave gyrosynchrotron emission for plasma diagnostics and three-dimensional modeling of solar flares and other astrophysical objects. This breakthrough became possible due to an apparently minor, technical development of fast gyrosynchrotron codes, which enormously reduce...
Preprint
Full-text available
The past decade has seen a dramatic increase of practical applications of the microwave gyrosyn-chrotron emission for plasma diagnostics and three-dimensional modeling of solar flares and other astrophysical objects. This breakthrough turned out to become possible due to apparently minor, technical development of Fast Gyrosynchrotron Codes, which e...
Article
Full-text available
The phenomenon of quasi-periodic pulsations (QPPs) in solar and stellar flares has been known for over 50 years and significant progress has been made in this research area. It has become clear that QPPs are not rare—they are found in many flares and, therefore, robust flare models should reproduce their properties in a natural way. At least fiftee...
Article
Full-text available
The solar atmosphere contains thermal plasma at a wide range of temperatures. This plasma is often quantified, in both observations and models, by a differential emission measure (DEM). The DEM is a distribution of the thermal electron density squared over temperature. In observations, the DEM is computed along a line of sight, while in the modelin...
Article
Full-text available
Solar and stellar flares are powerful events which produce intense radiation across the electromagnetic spectrum. Multiwavelength observations are highly important for understanding the nature of flares, because different flare-related processes reveal themselves in different spectral ranges. To study the correlation between thermal and nonthermal...
Preprint
Full-text available
Thermal plasma of solar atmosphere includes a wide range of temperatures. This plasma is often quantified, both in observations and models, by a differential emission measure (DEM). DEM is a distribution of the thermal electron density square over temperature. In observations, the DEM is computed along a line of sight, while in the modeling -- over...
Preprint
Full-text available
Solar and stellar flares are powerful events which produce intense radiation across the electromagnetic spectrum. Multiwavelength observations are highly important for understanding the nature of flares, because different flare-related processes reveal themselves in different spectral ranges. To study the correlation between thermal and nonthermal...
Poster
Full-text available
Solar low-frequency radio emission demonstrates a variety of fine temporal and spectral structures. The Low-Frequency Array (LOFAR) has offered unprecedented opportunities for studying these structures, not only providing the dynamic spectra with high resolution, but also allowing to determine the spatial characteristics of the emission sources and...
Article
Full-text available
The question why the solar corona is much hotter than the visible solar surface still puzzles solar researchers. Most theories of the coronal heating involve a tight coupling between the coronal magnetic field and the associated thermal structure. This coupling is based on two facts: (i) the magnetic field is the main source of the energy in the co...
Preprint
Full-text available
The question why the solar corona is much hotter than the visible solar surface still puzzles solar researchers. Most theories of the coronal heating involve a tight coupling between the coronal magnetic field and the associated thermal structure. This coupling is based on two facts: (i) the magnetic field is the main source of the energy in the co...
Article
Full-text available
Characterized by cyclic axisymmetric perturbations to both the magnetic and fluid parameters, magnetohydrodynamic fast sausage modes (FSMs) have proven useful for solar coronal seismology given their strong dispersion. This review starts by summarizing the dispersive properties of the FSMs in the canonical configuration where the equilibrium quanti...
Preprint
Full-text available
Characterized by cyclic axisymmetric perturbations to both the magnetic and fluid parameters, magnetohydrodynamic fast sausage modes (FSMs) have proven useful for solar coronal seismology given their strong dispersion. This review starts by summarizing the dispersive properties of the FSMs in the canoni-cal configuration where the equilibrium quant...
Preprint
Full-text available
Drift-pair bursts are an unusual type of solar low-frequency radio emission, which appear in the dynamic spectra as two parallel drifting bright stripes separated in time. Recent imaging spectroscopy observations allowed for the quantitative characterization of the drifting pairs in terms of source size, position, and evolution. Here, the drift-pai...
Article
Full-text available
Drift-pair bursts are an unusual type of solar low-frequency radio emission, which appear in the dynamic spectra as two parallel drifting bright stripes separated in time. Recent imaging spectroscopy observations allowed for the quantitative characterization of the drifting pairs in terms of source size, position, and evolution. Here, the drift-pai...
Preprint
Full-text available
Drift pairs are an unusual type of fine structure sometimes observed in dynamic spectra of solar radio emission. They appear as two identical short narrowband drifting stripes separated in time; both positive and negative frequency drifts are observed. Using the Low Frequency Array (LOFAR), we report unique observations of a cluster of drift pair b...
Article
Full-text available
Drift pairs are an unusual type of fine structure sometimes observed in dynamic spectra of solar radio emission. They appear as two identical short narrowband drifting stripes separated in time; both positive and negative frequency drifts are observed. Using the Low Frequency Array (LOFAR), we report unique observations of a cluster of drift pair b...
Article
Full-text available
Low-frequency radio observations make it possible to study the solar corona at distances up to 2–3 R ☉. Frequency of plasma emission is a proxy for electron density of the emitting plasma and, therefore, observations of solar radio bursts can be used to probe the density structure of the outer corona. In this study, positions of solar radio sources...
Article
Full-text available
Solar radio emission features a large number of fine structures demonstrating great variability in frequency and time. We present spatially resolved spectral radio observations of type IIIb bursts in the 30 − 80 MHz range made by the Low Frequency Array (LOFAR). The bursts show well-defined fine frequency structuring called "stria" bursts. The spat...
Conference Paper
Full-text available
Using the Low Frequency Array (LOFAR), we analyse the source sizes and locations of the fine frequency structuresin a solar radio burst. The high time resolution allows us to determine the location and the size of the radioemission source, and its evolution with time, following the radio emission propagation through the solar corona.It is found tha...
Preprint
Full-text available
Solar radio emission features a large number of fine structures demonstrating great variability in frequency and time. We present spatially resolved spectral radio observations of type IIIb bursts in the $30-80$ MHz range made by the Low Frequency Array (LOFAR). The bursts show well-defined fine frequency structuring called "stria" bursts. The spat...
Conference Paper
Full-text available
We investigate frequency-position structure of radio sources in solar type III and type IV bursts in the frequency range 30-50 MHz observed by LOFAR. These sources are produced by fundamental and harmonic plasma emission induced by propagating suprathermal electrons. Therefore, the frequency is a proxy for the electron density in the emitting plasm...
Conference Paper
Full-text available
Using the Low Frequency Array (LOFAR), we analyse the source sizes and locations of the fine frequency structures in a solar radio burst. The high time resolution allows us to determine the location and the size of the radio emission source, and its evolution with time, following the radio emission propagation through the solar corona. It is found...
Article
Full-text available
This work demonstrates the possibility of magnetic field topology investigations using microwave polarimetric observations. We study a solar flare of GOES M1.7 class that occurred on 11 February, 2014. This flare revealed a clear signature of spatial inversion of the radio emission polarization sign. We show that the observed polarization pattern c...
Article
The study of time-dependent solar active region (AR) morphology and its relation to eruptive events requires analysis of imaging data obtained in multiple wavelength domains with differing spatial and time resolution, ideally in combination with 3D physical models. To facilitate this goal, we have undertaken a major enhancement of our IDL-based sim...
Article
Full-text available
The original version of this article contained errors in Refs 15, 27, 32, 33 and 43, which were incorrectly given with the wrong journal name "Solid Phys." rather than the correct "Sol. Phys.". This has now been corrected in the PDF and HTML versions of the article.
Article
Full-text available
Solar radio observations provide a unique diagnostic of the outer solar atmosphere. However, the inhomogeneous turbulent corona strongly affects the propagation of the emitted radio waves, so decoupling the intrinsic properties of the emitting source from the effects of radio wave propagation has long been a major challenge in solar physics. Here w...
Poster
Full-text available
Using an unprecedented set of coordinated observations, from a suite of instruments, we here report on a hitherto largely overlooked energy component-the kinetic energy associated with small-scale turbulent mass motions. We show that the spatial location of, and timing of the peak in, turbulent kinetic energy together provide persuasive evidence th...
Article
Full-text available
Regular observations of active processes in the solar atmosphere have been started using the first stage of the multiwave Siberian Radioheliograph (SRH), a T-shaped 48-antenna array with a 4–8 GHz operating frequency range and a 10 MHz instantaneous receiving band. Antennas are mounted on the central antenna posts of the Siberian Solar Radio Telesc...
Article
Full-text available
Regular observations of active processes in the solar atmosphere have been started using the first stage of the multiwave Siberian Radioheliograph (SRH), a T-shaped 48-antenna array with a 4–8 GHz operating frequency range and a 10 MHz instantaneous receiving band. Antennas are set on the central antenna posts of the Siberian Solar Radio Telescope....
Article
Full-text available
The energy released in solar flares derives from a reconfiguration of magnetic fields to a lower energy state, and is manifested in several forms, including bulk kinetic energy of the coronal mass ejection, acceleration of electrons and ions, and enhanced thermal energy that is ultimately radiated away across the electromagnetic spectrum from optic...
Article
Full-text available
We present the results of a series of short radio observations of six ultracool dwarfs made using the upgraded VLA in S (2--4GHz) and C (4--7GHz) bands. LSR J1835+3259 exhibits a 100 percent right-hand circularly polarised burst which shows intense narrowband features with a fast negative frequency drift of about $-30$ MHz $\textrm{s}^{-1}$. They a...
Article
Full-text available
Microwave gyrosynchrotron radio emission generated by nonthermal electrons in twisted magnetic loops is modelled using the recently developed simulation tool GX Simulator. We consider isotropic and anisotropic pitch-angle distributions. The main scope of the work is to understand impact of the magnetic field twisted topology on resulted radio emiss...
Article
Full-text available
In this paper, we produce synthetic radio views on simulated flux ropes in the solar corona, where finite-beta magnetohydrodynamic (MHD) simulations serve to mimic the flux rope formation stages, as well as their stable endstates. These endstates represent twisted flux ropes where balancing Lorentz forces, gravity and pressure gradients determine t...
Article
Full-text available
Aurorae are detected from all the magnetized planets in our Solar System, including Earth. They are powered by magnetospheric current systems that lead to the precipitation of energetic electrons into the high-latitude regions of the upper atmosphere. In the case of the gas-giant planets, these aurorae include highly polarized radio emission at kil...
Article
Full-text available
Radio observations of solar flares often reveal various periodic or quasi-periodic oscillations. Most likely, these oscillations are caused by magnetohydrodynamic (MHD) oscillations of flaring loops which modulate the emission. Interpretation of the observations requires comparing them with simulations. We simulate the gyrosynchrotron radio emissio...
Article
Full-text available
We examined the polarization of the microwave flaring emission and its modulation by the fast sausage standing wave using a linear 3D magnetohydrodynamic model of a plasma cylinder. We analized the effects of the line-of-sight angle on the perturbations of the gyrosynchrotron intensity for two models: a base model with strong Razin suppression and...
Article
Full-text available
We have undertaken a major enhancement of our IDL-based simulation tools developed earlier for modeling microwave and X-ray emission. The object-based architecture provides an interactive graphical user interface that allows the user to import photospheric magnetic field maps and perform magnetic field extrapolations to almost instantly generate 3D...
Article
Full-text available
We investigate in detail the 21 May 2004 flare using simultaneous observations of the Nobeyama Radioheliograph, Nobeyama Radiopolarimeters, Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Solar and Heliospheric Observatory (SOHO). The flare images in different spectral ranges reveal the presence of a well-defined single flaring lo...
Article
Full-text available
Currently there is a concern about ability of the classical thermal (Maxwellian) distribution to describe quasi-steady-state plasma in solar atmosphere including active regions. In particular, other distributions have been proposed to better fit observations, for example, kappa- and $n$-distributions. If present, these distributions will generate r...
Article
The observations were conducted with the NRAO Very Large Array in the period 09 August-09 September 2009 using the standard continuum mode with 2x50MHz contiguous bands. (1 data file).
Article
Full-text available
Aims. We aim to increase the sample of ultracool dwarfs studied in the radio domain to allow a more statistically significant understanding of the physical conditions associated with these magnetically active objects. Methods. We conducted a volume-limited survey at 4.9 GHz of 32 nearby ultracool dwarfs with spectral types covering the range M7–T...
Article
Full-text available
We investigate the formation of zebra-like fine spectral structures (consisting of several parallel bands in the dynamic spectrum) in the Jovian broadband kilometric radiation; such radio bursts were observed by Cassini in 2000/2001. We assume that the emission is generated due to a plasma mechanism in the Io plasma torus. We have shown that the do...
Article
Full-text available
Addressing many key problems in solar physics requires detailed analysis of non-simultaneous imaging data obtained in various wavelength domains with different spatial resolution and their comparison with each other supplied by advanced 3D physical models. To facilitate achieving this goal, we have undertaken a major enhancement and improvements of...
Article
Full-text available
We present the numerical simulations for an electron-beam-driven and loss-cone-driven electron-cyclotron maser (ECM) with different plasma parameters and different magnetic field strengths for a relatively small region and short time-scale in an attempt to interpret the recent discovered intense radio emission from ultracool dwarfs. We find that a...
Article
Full-text available
The electron-cyclotron maser instability is widespread in the Universe, producing, e.g., radio emission of the magnetized planets and cool substellar objects. Diagnosing the parameters of astrophysical radio sources requires comprehensive nonlinear simulations of the radiation process. We simulate the electron-cyclotron maser instability in a very...
Article
Full-text available
Microwave emission of solar flares is formed primarily by incoherent gyrosynchrotron radiation generated by accelerated electrons in coronal magnetic loops. The resulting emission depends on many factors, including pitch-angle distribution of the emitting electrons and the source geometry. In this work, we perform systematic simulations of solar mi...
Article
The kinetics of beam electron precipitation from the top of a loop into the solar atmosphere with density gradients and an increasing magnetic field have been generally described. The Fokker-Planck equations are solved with regard to Coulomb collisions and the effect of the electric field induced by this beam. The photon spectra and polarization de...
Article
In this paper we discuss the effects of different energy loss mechanisms on resulting hard X-ray and MW emission of beam electrons injected in the loop top in the corona and precipitating into loop footpoints. For this purpose we use numeric solutions of Fokker-Planck equation considering collisional and Ohmic energy losses and anisotropic scatteri...
Conference Paper
Currently, and soon-to-be, available sophisticated 3D models of particle acceleration and transport in solar flares require a new level of user-friendly visualization and analysis tools allowing quick and easy adjustment of the model parameters and computation of realistic radiation patterns (images, spectra, polarization, etc). We report the curre...
Article
Full-text available
Recently, a number of ultracool dwarfs have been found to produce periodic radio bursts with high brightness temperature and polarization degree; the emission properties are similar to the auroral radio emissions of the magnetized planets of the Solar System. We simulate the dynamic spectra of radio emission from ultracool dwarfs. The emission is a...
Article
Full-text available
We simulate the dynamic spectra of the radio emission from a brown dwarf. The emission is produced due to the electron-cyclotron maser instability. Two source models are considered: the emission caused by interaction with a satellite and the emission from a sector of active longitudes. We have found that for the dwarf TVLM513 the model of an active...
Article
Full-text available
We perform 3D simulations of gyrosynchrotron emission from solar flaring loops. The full polarization transfer equation is solved; the radio brightness maps and spectral dependences of the Stokes parameters of the emission are obtained. We discuss the conditions required to detect the linear polarization of the solar microwave emission by the exist...
Article
Full-text available
Microwave emission of solar flares is formed primarily by incoherent gyrosynchrotron radiation generated by accelerated electrons in coronal magnetic loops. The resulting emission depends on many factors, including pitch-angle distribution of the emitting electrons and the source geometry. In this work, we perform systematic simulations of solar mi...