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19 results on '"Bogod, V. M."'

2. Modeling of the sunspot-associated microwave emission using a new method of DEM inversion

Author

Alissandrakis, C. E., Bogod, V. M., Kaltman, T. I., Patsourakos, S., and Peterova, N. G.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

We developed a method to compute the temperature and density structure along the line of sight by inversion of the differential emission measure (DEM), under the assumptions of stratification and hydrostatic equilibrium. We applied this method to the DEM obtained from AIA observations and used the results, together with potential extrapolations of the photosheric magnetic field, to compute the microwave emission of three sunspots, which we compared with observations from the RATAN-600 radio telescope and the Nobeyama Radioheliograph (NoRH). Our DEM based models reproduced very well the observations of the moderate-size spot on October 2011 and within 25% the data of a similar sized spot on March 2016, but predicted too low values for the big spot of April 14, 2016. The latter was better fitted by a constant conductive flux atmospheric model which, however, could not reproduce the peak brightness temperature of $4.7\times10^6$ K and the shape of the source at the NoRH frequency. We propose that these deviations could be due to low intensity non-thermal emission associated to a moving pore and to an opposite polarity light bridge. We also found that the double structure of the big spot at high RATAN-600 frequencies could be interpreted in terms of the variation of the angle between the magnetic field and the line of sight along the sunspot., Comment: Accepted for publication in Solar Physics

Published
2018
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4. RATAN-600 Observations of Small Scale Structures with High Spectral Resolution

Author

Bogod, V. M., Alissandrakis, C. E., Kaltman, T. I., and Tokhchukova, S. Kh.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

We present observations of quiet-sun small-scale structures (SSS) in the microwave range with the {\it Radio Astronomical Telescope of the Academy of Sciences 600} (RATAN-600) spectral-polarization facility in a wide range of frequencies. SSS are regularly recorded in routine observations of the large reflector-type radio telescope and represent manifestations in the radio range of various structures of the quiet-sun: supergranulation network, bright points, plage patches and so on. A comparison with with images from the {\it Solar Dynamics Observatory} (SDO) showed that the microwave emission comes from a region extending from the chromosphere to the low transition region. We measured the properties of the SSS as well as the degree of circular polarization averaged over the beam of the radio telescope and from this we estimated the magnetic field at the formation level of the radiation., Comment: Solar Physics, in press

Published
2014
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5. Comment on 'CAWSES November 7-8, 2004, superstorm: Complex solar and interplanetary features in the post-solar maximum phase' by B. T. Tsurutani, E. Echer, F. L. Guarnieri, and J. U. Kozyra

Author

Eselevich, V. G., Bogod, V. M., Chashey, I. V., Eselevich, M. V., and Yermolaev, Yu. I.

Subjects
Physics - Space Physics
Abstract

Recently Tsurutani et al., (2008) (Paper 1) analyzed the complex interplanetary structures during 7 to 8 November, 2004 to identify their properties as well as resultant geomagnetic effects and the solar origins. Besides mentioned paper by Gopalswamy et al., (2006) the solar and interplanetary sources of geomagnetic storm on 7-10 November, 2004 have also been discussed in details in series of other papers. Some conclusions of these works essentially differ from conclusions of the Paper 1 but have not been discussed by authors of Paper 1. In this comment we would like to discuss some of these distinctions., Comment: Submitted for publication in Geophysical Research Letters

Published
2008
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6. IX Russian-Finnish Symposium on Radio Astronomy 'Multi-wavelength investigations of solar and stellar activity and active galactic nuclei'

Author

Abramov-Maximov, V. E., Arshakian, T. G., Bogod, V. M., Borovik, V. N., Burenkov, A. N., Bursov, N. N., Doroshenko, V. T., Efimov, Yu. S., Fabrika, S. N., Golubchina, O. A., Gorshkov, A. G., Gosachinskij, I. V., Harinov, M., Hovatta, T., Kaltman, T. I., Korzhavin, A. N., Kotelnikov, V., Kovalev, Yu. A., Kouprianova, E. G., Lahteenmaki, A., Lehto, H. J., Mingaliev, M. G., Modin, E. V., Nieppola, E., Parijskij, Yu. N., Riehokainen, A., Soboleva, N. S., Stepanov, A. V., Tlatov, A. G., Torniainen, I., Tornikoski, M., Trushkin, S. A., Valtaoja, E., Verkhodanov, O. V., Volvach, A. E., and Zinchenko, I. I.

Subjects
Astrophysics
Abstract

The IX Russian-Finnish Symposium on Radio Astronomy was held in Special astrophysical observatory RAS in Nizhnij Arkhyz, Russia on 15-20 October 2006. It was dedicated to the two-side collaboration in the field of multi-wavelength investigations of solar radio emission, studies of polar regions of the Sun, studies of stellar activity, AGNs, quasars and BL Lac objects in radio bands from millimeter to decimetre wavelengths with RATAN-600, Metsahovi 14m, RT32m radio telescope and VLBI systems. Here abstracts of all forty papers are given. The Web-site of the Symposium is http://cats.sao.ru/~satr/RFSymp/ ., Comment: 41 pages, abstracts of the Symposium papers

Published
2006

7. Analysis of polarized microwave emission of Flare-Productive Active Region 9415

Author

Bogod, V. M., Gelfreikh, G. B., Drago, F. Ch., Maximov, V. P., Nindos, A., Kaltman, T. I., Ryabov, B. I., and Tokhchukova, S. Kh.

Subjects
Astrophysics
Abstract

The results of the microwave observations of the Sun made with the RATAN-600 have shown the existence of many types of spectral peculiarities in polarized emission of active regions, which produce powerful flares. These phenomena happen at microwaves and reflect inhomogeneous structure of magnetic field in magnetospheres of flaring active regions in wide range of heights above the photosphere. In this presentation we demonstrate an analysis of the AR 9415 during all the period of its passage across the solar disk. Results of the study point out to existence of different scenarios of circular polarization variations in the radio wave band. Here, we separated the phenomenon of the cyclotron emission passage through the quasi-transverse magnetic field (QT-region) and several effects connected with flare activity of active region. New observational data are presented and compared with the data of several observatories: SSRT, NoRH, MDI SOHO, GOES and MEES. The preliminary interpretation of the phenomena are given., Comment: 26 pages, 13 Postscript figures for better resolution pics, see http://www.sao.ru/hq/sun/pdf/paper9415.pdf

Published
2003

13. Solar and Heliospheric Phenomena in October–November 2003: Causes and Effects

Author

Veselovsky, I. S., Panasyuk, M. I., Avdyushin, S. I., Bazilevskaya, G. A., Belov, A. V., Bogachev, S. A., Bogod, V. M., Bogomolov, A. V., Bothmer, V., Boyarchuk, K. A., Vashenyuk, E. V., Vlasov, V. I., Gnezdilov, A. A., Gorgutsa, R. V., Grechnev, V. V., Denisov, Yu. I., Dmitriev, A. V., Dryer, M., Yermolaev, Yu. I., Eroshenko, E. A., Zherebtsov, G. A., Zhitnik, I. A., Zhukov, A. N., Zastenker, G. N., Zelenyi, L. M., Zeldovich, M. A., Ivanov-Kholodnyi, G. S., Ignat'ev, A. P., Ishkov, V. N., Kolomiytsev, O. P., Krasheninnikov, I. A., Kudela, K., Kuzhevsky, B. M., Kuzin, S. V., Kuznetsov, V. D., Kuznetsov, S. N., Kurt, V. G., Lazutin, L. L., Leshchenko, L. N., Litvak, M. L., Logachev, Yu. I., Lawrence, G., Markeev, A. K., Makhmutov, V. S., Mitrofanov, A. V., Mitrofanov, I. G., Morozov, O. V., Myagkova, I. N., Nusinov, A. A., Oparin, S. N., Panasenco, O. A., Pertsov, A. A., Petrukovich, A. A., Podorol'sky, A. N., Romashets, E. P., Svertilov, S. I., Svidsky, P. M., Svirzhevskaya, A. K., Svirzhevsky, N. S., Slemzin, V. A., Smith, Z., Sobel'man, I. I., Sobolev, D. E., Stozhkov, Yu. I., Suvorova, A. V., Sukhodrev, N. K., Tindo, I. P., Tokhchukova, S. Kh., Fomichev, V. V., Chashey, I. V., Chertok, I. M., Shishov, V. I., Yushkov, B. Yu., Yakovchouk, O. S., and Yanke, V. G.

Published
2004
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16. Coronal magnetography of an active region from microwave polarization inversion

Author

Ryabov, B. I., Pilyeva, N. A., Alissandrakis, C. E., Shibasaki, K., Bogod, V. M., Garaimov, V. I., and Gelfreikh, G. B.

Subjects
magnetic-fields, radio observations, emission
Abstract

The microwave circular polarization of the active region (AR) NOAA 7260 on 21-23 August 1992 is analyzed, Two-dimensional images at 1.76 cm with spatial resolution of theta = 10 " from the Nobeyama radioheliograph and one-dimensional scans at 9 wavelengths in the range of 1.81-3.43 cm and theta = 16.3 "-31.1 " from the radio telescope RATAN-600 were used. An inversion of the sense of circular polarization through the wavelength range was recorded on 22 August. It is shown that both the wavelength and the time dependence of the inversion are consistent with quasi-transverse (QT) propagation of the radiation in the solar corona. From this, the strength of the coronal magnetic field in the active region was found to be H = 20 - 65 G at a height of h = (5.7-8.7) x 10(9) cm above the photosphere on 22 and 30 August and 125 G at the lower height of (3.7-6.4) x 10(9) cm on 23 August. We present a new technique, based on the radio mapping (in both Stokes I and V) of an AR undergoing circular polarization inversion; applying this method to the Nobeyama data we obtained, for the first time, a magnetogram of the coronal magnetic field. For AR 7260 we found values in the range of 70-100 G at heights of (4-6) x 10(9) cm on 23 August, adopting a constant value of N L-alpha (where N is the electron density and L-alpha is the scale of the coronal field divergence) of 2.5 x 10(18) cm(-2). We compare our results with force-free extrapolations of the photospheric magnetic field from a MSFC magnetogram obtained on 20 August. Solar Physics

Published
1999

19. Solar and Heliospheric Phenomena in October–November 2003: Causes and Effects.

Author

Vesetovsky, I. S., Panasyuk, M. I., Avdyushin, S.I., Bazitevskaya, G. A., Betov, A. V., Bogachev, S. A., Bogod, V. M., ogomolov, A. V. B, Bothmer, V., Boyarchuk, K. A., Vashenyuk, E. V., Vlasov, V. I., Gnezditov, A. A., Gorgutsa, R. V., Grechnev, V. V., Denisov, Yu. I., Dmitriev, A. V., Dryer, M., Yermolaev, Yu. I., and Eroshenko, E. A.

Subjects
SUN, HELIOSPHERE, MAGNETIC storms, GEOMAGNETISM, SOLAR flares, SOLAR activity
Abstract

We present new observational data on the phenomena of extremely high activity on the Sun and in the heliosphere that took place in October-November 2003. A large variety of solar and heliospheric parameters give evidence that the interval under consideration is unique over the entire observation time. Based on these data, comparing them with similar situations in the past and using available theoretical concepts, we discuss possible cause-and-effect connections between the processes observed. The paper includes the first results and conclusions derived by the collaboration "Solar Extreme Events-2003" organized in Russia for detailed investigations of these events. As a result of our consideration, it is beyond question that the physical causes of solar and heliospheric phenomena in October-November 2003 are not exclusively local and do not belong only to the active regions and solar atmosphere above them. The energy reservoirs and driving forces of these processes have a more global nature. In general, they are hidden from an observer, since ultimately their sources lie in the subphotospheric layers of the Sun, where changes that are fast and difficult to predict can sometimes take place (and indeed they do). Solar flares can serve as sufficiently good tracers of these sudden changes and reconstructions on the Sun, although one can still find other diagnostic indicators among the parameters of magnetic fields, motions of matter, and emission characteristics. [ABSTRACT FROM AUTHOR]

Published
2004
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