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V. V. Smirnova

Publications and source records attributed to V. V. Smirnova.

6 recordsLinked to original sources
arXiv2026

Post-impulsive millimeter emission of the 2022-05-04 solar flare

The present work aims at analyzing the nature of millimeter (mm) emission observed during the post-impulsive phase of the solar flare SOL2022-05-04T08:45 (M5.7), detected by the RT-7.5 radio telescope of the Bauman Moscow State Technical University at 93 GHz. We investigate the relationship of mm and extreme ultraviolet (EUV) emission with variations in the temperature and coronal plasma emission measure obtained from SDO/AIA and GOES data. The results show that the enhanced mm emission at the post-impulsive phase of the flare coincides with the increase of EUV emission, indicating a connection with moderately hot (~1 MK) plasma. Based on the calculation of the differential emission measure, we determine the parameters of the post-impulsive flare plasma and conclude that the optically thin coronal plasma may contribute of about 20% to the mm emission.

astro-ph.SR↗
arXiv2023

Pre-impulsive and Impulsive Phases of the Sub-Terahertz Flare of March 28, 2022

Properties of the solar radio spectrum, as well as the temporal profiles of flare emission, indicate the thermal nature of the sub-terahertz (sub-THz) component observed as the growth of radio emission in the frequency range of 100-1000 GHz. The sub-THz flare onset can be ahead of the impulsive phase for several minutes. However, the origin of the pre-impulsive and impulsive sub-THz emission remains unclear. The present work is devoted to a detailed analysis of the M4.0 X-class solar flare observed on March 28, 2022 with the Bauman Moscow State Technical University Radio Telescope RT-7.5 at 93 GHz. We supply these data with multiwavelength solar observations in the X-ray (GOES, GBM/Fermi), extreme ultraviolet (AIA/SDO), and microwave ranges. The differential emission measure (DEM) responsible for EUV emission is determined by solving the inverse problem based on the AIA/SDO data. Using the DEM and assuming a thermal free-free emission mechanism in pre-impulsive and impulsive phases, we calculated the millimeter emission flux of coronal plasma of the flare source, which turned out to be much smaller than the observed values. We concluded that electrons accelerated in the corona and heat fluxes from the coronal loop top cannot be responsible for heating the sub-THz emission source located in the transition region and upper chromosphere. A possible origin of chromospheric heating in the pre-impulsive phase of the solar flare is discussed.

astro-ph.SR↗
arXiv2018

Long-Term Oscillations of Sunspots and a Special Class of Artifacts in SOHO(MDI) and SDO(HMI) Data

A specific type of artifacts, that originate due to displacement of the image of a moving object along the digital (pixel) matrix of receiver are analyzed in detail. The criteria of appearance and the influence of these artifacts on the study of long-term oscillations of sunspots are deduced. The obtained criteria suggest us methods for reduction or even elimination of these artifacts. It is shown that the use of integral parameters can be very effective against the artifact distortions. The simultaneous observations of sunspot magnetic field and ultraviolet intensity of the umbra have given the same periods for the long-term oscillations. In this way the real physical nature of the oscillatory process, which is independent of the artifacts have been confirmed again. A number of examples considered here confirm the dependence between the periods of main mode of the sunspot magnetic field long-term oscillations and its strength. The dependence was derived earlier from both the observations and the theoretical model of the shallow sunspot. The anti-phase behavior of time variations of sunspot umbra area and magnetic field of the sunspot demonstrates that the umbra of sunspot moves in long-term oscillations as a whole: all its points oscillate with the same phase.

astro-ph.SR↗
arXiv2005

The Bayesian Effects in Measurement of the Asymmetry of Poisson Flows

As it follows from the interrelation of Gamma and Poisson distributions the observed value of asymmetry for Poisson flows of events has the bias. The Monte Carlo experiment confirms the presence of this bias between the observed and initial asymmetries. The obtained results allow to correct the estimation of the asymmetry of flow rates.

physics.data-an↗
arXiv2004

Statistically dual distributions and estimation of the parameters

The reconstruction of the parameter of the model by the measurement of the random variable depending on this parameter is one of the main tasks of statistics. In the paper the notion of the statistically dual distributions is introduced. The approach, based on the properties of the statistically dual distributions, to resolving of the given task is proposed.

math.ST↗