Zakharenko V.V.,Ukrainian Academy of Sciences |
Vasylieva I.Y.,Ukrainian Academy of Sciences |
Konovalenko A.A.,Ukrainian Academy of Sciences |
Ulyanov O.M.,Ukrainian Academy of Sciences |
And 7 more authors.
Monthly Notices of the Royal Astronomical Society
The study of pulsars at the lowest radio frequencies observable from the ground (10-30 MHz) is complicated by strong interstellar (dispersion, scattering) and ionospheric (scintillation, refraction) propagation effects, as well as intense Galactic background noise and interference. However, it permits us to measure interstellar plasma parameters (the effects of which increase by a power of two to >4 times the wavelength), the spectrum and the pulse profile at low frequencies more accurately. Up to now, only ~10 pulsars have been successfully detected at these frequencies. The recent upgrade of the receivers at the Ukrainian T-shaped Radio telescope, second modification (UTR-2) has increased its sensitivity and motivated a new search for pulsed radio emissions. In this work we carried out a survey of known pulsars with declination above -10°, period >0.1 s and dispersion measure (DM) < 30 pc cm. -3, i.e. a sample of 74 sources. Our goal was either to detect pulsars not recorded before in the decametre range or to identify factors that prevent their detection. As a result, we have detected the radio emission of 40 pulsars, i.e. 55 per cent of the observed sample. For 30 of them, this was a first detection at these frequencies. Parameters of their average profiles have been calculated, including the intrinsic widening of the pulse (not due to interstellar scattering) with decreasing frequency. Furthermore, two pulsars beyond the selected DM (B0138+59 with DM ≈ 35 pc cm. -3 and B0525+21 with DM ≈51 pc cm. -3) were also detected. Our results indicate that there is still room to detect new transient and pulsed sources with low-frequency observations. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Source
Konovalenko A.A.,Kharkov National University of Radio Electronics |
Kalinichenko N.N.,Kharkov National University of Radio Electronics |
Rucker H.O.,Space Research Institute |
Lecacheux A.,French National Center for Scientific Research |
And 11 more authors.
We report the history of the first recorded ground-based radio detection of Saturns lightning using the Ukrainian UTR-2 radiotelescope at frequencies from 20 to 25. MHz. The observations were performed between 29 January and 3 February 2006, during which lighting activity (E-storm) on Saturn was detected by the radio experiment onboard Cassini spacecraft. The minimum detectable flux density (1σ-level) at UTR-2 reached 40. Jy (1Jy=10-26Wm-2Hz-1) for narrowband observations (Δf=10kHz) and 4. Jy for broadband observations (Δf=1MHz), for an effective telescope area of ≈100,000m2 and integration time of 20. ms. Selection criteria including comparison of simultaneous ON/OFF-source observations were applied to distinguish detection of lightning-associated radio pulses from interference. This allowed us to identify about 70 events with signal-to-noise ratio more than 5. Measured flux densities (between 50 and 700. Jy) and burst durations (between 60 and 220. ms) are in good agreement with extrapolation of previous Cassini measurements to a ground-based observer. This first detection demonstrates the possibility of Solar System planetary lightning studies using large, present and future ground-based radio instruments. The developed methods of observations and identification criteria are also implemented on the UTR-2 radio telescope for the investigation of the next Saturns storms. Together with recently published UTR-2 measurements of activity measured after the 2006 storm reported here, the results have significant implications for detectable planetary radio emission in our Solar System and beyond. © 2012 Elsevier Inc. Source
Zakharenko V.,Kharkov National University of Radio Electronics |
Mylostna C.,Kharkov National University of Radio Electronics |
Konovalenko A.,Kharkov National University of Radio Electronics |
Zarka P.,University Paris Diderot |
And 20 more authors.
Planetary and Space Science
In late 2007, Saturn electrostatic discharges (SED) were simultaneously observed at the radio telescope UTR-2 and with the Cassini spacecraft. Observations at UTR-2 were performed with a multichannel receiver in the frequency range 1233 MHz, and those performed on Cassini - with a swept frequency receiver that is part of the RPWS (Radio and Plasma Wave Science) instrument in the frequency band 1.816 MHz. We got a very good coincidence between data of UTR-2 and Cassini. It is shown for the first time that ground-based radio astronomy lets us detect Saturns lightning with a high degree of reliability despite terrestrial interferences. This is the necessary basis for further detailed study of the temporal and spectral characteristics of the SEDs with ground based radio telescopes. Based on six observation sessions, several parameters of SEDs were determined, in particularly a correlation of 0.77±0.15 between the average intensity of storms and the e-folding time. © 2011 Elsevier Ltd. All rights reserved. Source
Wygant J.R.,University of Minnesota |
Bonnell J.W.,University of California at Berkeley |
Goetz K.,University of Minnesota |
Ergun R.E.,University of Colorado at Boulder |
And 35 more authors.
Space Science Reviews
The Electric Fields and Waves (EFW) Instruments on the two Radiation Belt Storm Probe (RBSP) spacecraft (recently renamed the Van Allen Probes) are designed to measure three dimensional quasi-static and low frequency electric fields and waves associated with the major mechanisms responsible for the acceleration of energetic charged particles in the inner magnetosphere of the Earth. For this measurement, the instrument uses two pairs of spherical double probe sensors at the ends of orthogonal centripetally deployed booms in the spin plane with tip-to-tip separations of 100 meters. The third component of the electric field is measured by two spherical sensors separated by ∼15 m, deployed at the ends of two stacer booms oppositely directed along the spin axis of the spacecraft. The instrument provides a continuous stream of measurements over the entire orbit of the low frequency electric field vector at 32 samples/s in a survey mode. This survey mode also includes measurements of spacecraft potential to provide information on thermal electron plasma variations and structure. Survey mode spectral information allows the continuous evaluation of the peak value and spectral power in electric, magnetic and density fluctuations from several Hz to 6.5 kHz. On-board cross-spectral data allows the calculation of field-aligned wave Poynting flux along the magnetic field. For higher frequency waveform information, two different programmable burst memories are used with nominal sampling rates of 512 samples/s and 16 k samples/s. The EFW burst modes provide targeted measurements over brief time intervals of 3-d electric fields, 3-d wave magnetic fields (from the EMFISIS magnetic search coil sensors), and spacecraft potential. In the burst modes all six sensor-spacecraft potential measurements are telemetered enabling interferometric timing of small-scale plasma structures. In the first burst mode, the instrument stores all or a substantial fraction of the high frequency measurements in a 32 gigabyte burst memory. The sub-intervals to be downloaded are uplinked by ground command after inspection of instrument survey data and other information available on the ground. The second burst mode involves autonomous storing and playback of data controlled by flight software algorithms, which assess the "highest quality" events on the basis of instrument measurements and information from other instruments available on orbit. The EFW instrument provides 3-d wave electric field signals with a frequency response up to 400 kHz to the EMFISIS instrument for analysis and telemetry (Kletzing, et al. Space Sci. Rev. 2013). © 2013 The Author(s). Source
Lefeuvre F.,LPC2E |
Tanzi T.,Telecom ParisTech
2014 31th URSI General Assembly and Scientific Symposium, URSI GASS 2014
When a natural disaster occurs in a populated zone, a fast and effective organization of the disaster management is necessary to assist the affected population, reduce the number of victims and limit the economic impact. Radio science plays an important role in the first two weeks after a disaster strikes (the response phase). The paper deals with: (1) general aspects of disaster management, (2) radio communication and observation services in a nominal situation and during the response phase of a disaster at the time of space weather events, (3) Emergency management. © 2014 IEEE. Source