Ventspils International Radio Astronomy Center

Ventspils, Latvia

Ventspils International Radio Astronomy Center

Ventspils, Latvia
SEARCH FILTERS
Time filter
Source Type

Ryabov B.I.,Ventspils International Radio Astronomy Center | Bezrukov D.A.,Ventspils International Radio Astronomy Center | Kallunki J.,Aalto University
Latvian Journal of Physics and Technical Sciences | Year: 2017

The microwave regions with low brightness temperature are found to overlap the regions of the depressed coronal emission and open field lines at the periphery of two solar active regions (ARs). The imaging microwave observations of the Sun with the Nobeyama Radio heliograph at 1.76 cm, the MRO-14 radio telescope of Metsähovi Radio Observatory at 0.8 cm, and the RT-32 of Ventspils International Radio Astronomy Centre in the range 3.2-4.7 cm are used. To reduce the noise in the intensity distribution of the RT-32 maps of the Sun, one wavelet plane of "à trous" wavelet space decomposition is subtracted from each map. To locate the open-field regions, the full-Sun coronal magnetic fields with the potential field source surface (PFSS) model for RSS = 1.8 R are simulated. We conclude that the revealed LTRs present narrow coronal hole-like regions near two ARs and imply an extra investigation on the plasma outflow. © by B. I. Ryabov 2017.


Bogod V.M.,Russian Academy of Sciences | Peterova N.G.,Russian Academy of Sciences | Ryabov B.I.,Ventspils International Radio Astronomy Center | Topchilo N.A.,Saint Petersburg State University
Cosmic Research | Year: 2015

Observations are reviewed of active regions where radio emission depressions in radio sources above large sunspots is observed. The depression value can be significant and can reach 2000–4000 K relative to the temperature around a quiet Sun. However, the number of cases of strong depression is small, which is apparently related to the specific features and conditions of sunspot observations and the limited or restrict telescope possibilities of the present day. Usage of the RATAN-600 radio telescope with a high spectral resolution (1%) made it possible to establish that this phenomenon is observed in a limited wavelength range (1.7–3.0) cm. Owing to the special method of RATAN-600 polarization measurements, it has been indicated that the emission depression effect takes place in the ordinary o-mode emission, whereas the emission source above a sunspot is always brighter than the background in the extraordinary e-mode. Two new active regions where the depression phenomenon was registered have been considered, and a comparison with the data from the NoRH radioheliograph, SSRT, and spacecraft has been performed. The values of the magnetic fields above the sunspots at which the region of ordinary and extraordinary wave generation penetrates in the coronal temperature region have been measured. A depression phenomenon modeling, indicating that electron density decreases and the situation is similar to coronal holes, has been performed based on the set of observational data. Possible directions in the study of this phenomenon are discussed. © 2015, Pleiades Publishing, Ltd.


Ryabov B.I.,Ventspils International Radio Astronomy Center | Gary D.E.,New Jersey Institute of Technology | Peterova N.G.,Russian Academy of Sciences | Shibasaki K.,Nobeyama Solar Radio Observatory | Topchilo N.A.,Saint Petersburg State University
Solar Physics | Year: 2014

We analysed specific regions of reduced soft X-ray and microwave emission in five large isolated sunspots. The Nobeyama Radioheliograph 17 GHz observations reveal a local depression of microwave brightness in the peripheral area of the sunspots. The depression regions appear light (weak absorption) in the He 10830 Å line in areas with extended (open) field lines, as indicated by potential field source surface model (PFSS) extrapolations up to 1.5 R⊙. The observed depressions of 3 – 8 % in ordinary mode at 17 GHz are interpreted as resulting from free–free emission when the plasma density is lower by 5 – 10 %. Our model estimates show that the decrease in density in both the coronal and the lower layers above the depression region accounts for the depression. These depression regions lend themselves well to marking the location of outward plasma motions. © 2014, Springer Science+Business Media Dordrecht.


Bezrukov D.,Ventspils International Radio Astronomy Center | Bezrukov D.,University of Latvia | Ryabov B.,Ventspils International Radio Astronomy Center | Ryabov B.,University of Latvia | And 2 more authors.
Latvian Journal of Physics and Technical Sciences | Year: 2011

In the work, interpretation is given for a microwave source associated with a stable isolated sunspot as a sample to study the sharp changes in ordinary mode microwave emission. The appropriate microwave source of the solar active region NOAA 10325 was observed with the radio telescope RATAN-600 and the Nobeyama Radio Heliograph during March 30 - April 4, 2003. The radio emission brightness in ordinary mode is shown to be depressed below the brightness of the quiet Sun when the sunspot was near the solar disk centre (April 2-3) but sharply increased in the wavelength range 1.76-2.67 cm at the longitudes |θ| > 50°.Microwave radiation by gyroresonance mechanism is analysed in relation to the particular features of the images taken in He I 10830 Å chromospheric line (Chromospheric Helium-I Imaging Photometer) and EUV emission lines (Coronal Diagnostic Spectrometer). We have constructed a new model according to which above the sunspot's surroundings at the levels of gyroresonance emission the atmosphere is as cold as a "sunspot plume" (T ~ 105-106 K, N ~ 109 cm-3). As could be supposed from the He I line intensity, the central part of the sunspot atmosphere contains open magnetic field and rarefied plasma (N ~ 108 cm-3, T ~ 105.5- 106 K).


Nechaeva M.,Ventspils International Radio Astronomy Center | Antipenko A.,Radiophysical Research Institute RRI | Bezrukovs V.,Ventspils International Radio Astronomy Center | Bezrukov D.,Ventspils International Radio Astronomy Center | And 17 more authors.
Baltic Astronomy | Year: 2013

An experiment on radar location of space debris objects using of the method of VLBI was carried out in April, 2012. The radar VLBI experiment consisted in irradiation of some space debris objects (4 rocket stages and 5 inactive satellites) with a signal of the transmitter with RT-70 in Evpatoria, Ukraine. Reflected signals were received by a complex of radio telescopes in the VLBI mode. The following VLBI stations took part in the observations: Ventspils (RT-32), Urumqi (RT-25), Medicina (RT-32) and Simeiz (R.T-22). The experiment included measurements of the Doppler frequency shift and the delay for orbit refining, and measurements of the rotation period and sizes of objects by the amplitudes of output interferometer signals. The cross-correlation of VLBI-data is performed at a correlator NIRFI-4 of Radiophysical Research Institute (Nizhny Novgorod). Preliminary data processing resulted in the series of Doppler frequency shifts, which comprised the information on radial velocities of the objects. Some results of the experiment are presented.


Dugin N.,Radiophysical Research Institute RRI | Antipenko A.,Radiophysical Research Institute RRI | Bezrukovs V.,Ventspils International Radio Astronomy Center | Gavrilenko V.,Novgorod State University | And 7 more authors.
Baltic Astronomy | Year: 2013

Since 2012, the Radiophysical Research Institute and the Lobachevsky State University at Nizhny Novgorod, Russia and the Ventspils International Radio Astronomy Centre at Irbene, Latvia are making radio interferometric experiments on study of ionosphere parameters in a quiet (natural) state of medium and research of artificial turbulence of the ionosphere, heated by the emission from the SURA facility. Remote diagnostics of the ionosphere is implemented using a method of radio sounding by signals of navigation satellites in combination with the Very Long Baseline Interferometry (VLBI) method. As a result of spectral and correlation analysis, interferometric responses of the two-element (RRI-UNN) and three-element (RRI-UNN-Irbene) interferometers were received by observations of 12 satellites of the navigation systems GLONASS and GPS. Here the first results are reported.


Polevskis J.,Ventspils International Radio Astronomy Center | Krastins M.,Ventspils International Radio Astronomy Center | Korats G.,Ventspils International Radio Astronomy Center | Skorodumovs A.,Ventspils International Radio Astronomy Center | Trokss J.,Ventspils International Radio Astronomy Center
Latvian Journal of Physics and Technical Sciences | Year: 2012

The authors deal with the operation of Automatic Identification System (AIS) used in the marine traffic monitoring to broadcast messages containing information about the vessel: id, payload, size, speed, destination etc., meant primarily for avoidance of ship collisions. To extend the radius of AIS operation, it is envisaged to dispose its receivers on satellites. However, in space, due to a large coverage area, interfering factors are especially pronounced - such as packet collision, Doppler's shift and noise impact on AIS message receiving, pre-processing and decoding. To assess the quality of an AIS receiver's operation, a test was carried out in which, varying automatically frequency, amplitude, noise, and other parameters, the data on the ability of the receiver's ability to decode AIS signals are collected. In the work, both hardware- and software-based AIS decoders were tested. As a result, quite satisfactory statistics has been gathered - both on the common and the differing features of such decoders when operating in space. To obtain reliable data on the software-defined radio AIS receivers, further research is envisaged.


Bezrukov D.A.,Ventspils International Radio Astronomy Center | Ryabov B.I.,Ventspils International Radio Astronomy Center | Shibasaki K.,Nobeyama Radio Observatory
Baltic Astronomy | Year: 2012

On the base of the 17 GHz radio maps of the Sun taken with the Nobeyama Radio Heliograph we estimate plasma parameters in the specific region of the sunspot atmosphere in the active region AR 11312. This region of the sunspot atmosphere is characterized by the depletion in coronal emission (soft X-ray and EUV lines) and the reduced absorption in the a chromospheric line (HeI 1.083 μm). In the ordinary normal mode of 17 GHz emission the corresponding dark patch has the largest visibility near the central solar meridian. We infer that the reduced coronal plasma density of about 5 × 108 cm -3 is the characteristic feature of the dark patch.


Bezrukov D.,Ventspils International Radio Astronomy Center
Baltic Astronomy | Year: 2013

The article describes microwave observations of the Sun with the radio telescope RT-32 of the Ventspils International Radio Astronomy Center. The observations were performed using a multichannel spectral Polarimeter for the 6.3-9.4 GHz frequency range. A set of 2D microwave emission maps of the Sun for the Stokes I and V parameters has been obtained and analyzed.


Bezrukovs D.,Ventspils International Radio Astronomy Center
Baltic Astronomy | Year: 2011

A brief historical review of the development of solar physics and solar radio astronomy in Latvia and its current status is presented.

Loading Ventspils International Radio Astronomy Center collaborators
Loading Ventspils International Radio Astronomy Center collaborators