Zeitschriftenartikel zum Thema „Radio waves (Astronomy)“
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1
Ensslin, T. A. „ASTRONOMY: Radio Traces of Cosmic Shock Waves“. Science 314, Nr. 5800 (03.11.2006): 772–73. http://dx.doi.org/10.1126/science.1133949.
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Yang, Guang Pu, Liang Dong, Le Sheng He, Fa Xin Shen, Bin Tian und Sheng Yang Li. „A New Platform for Radio Astronomy Science Education“. Advances in Science and Technology 105 (April 2021): 179–83. http://dx.doi.org/10.4028/www.scientific.net/ast.105.179.
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Radio astronomy telescope can get information from invisible universe by receiving electromagnetic waves. Difference from optical telescopes, there exists many difficulties for making the public understanding the radio astronomy phenomenon. In this paper, we will introduce a new platform for radio astronomy science popularization education in order to help public know radio telescope and radio astronomy. The platform consists of a 0.8meter parabolic antenna, a wide bandwidth low noise amplifier (LNA) and a Software Defined Radio (SDR) terminal. Based on SDR terminal which covers the band from 70MHz to 6GHz, we can get some strong emissions such as the Neutral hydrogen, solar radio bursts and so on in this band. People can carry out many radio astronomy experiments focusing on science popularization by this platform. This new science education tool can interest high school students in science and technology, also students can understand how radio telescopes works.
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Spangler, S. R. „Interstellar Magnetohydrodynamic Waves as Revealed by Radio Astronomy“. Symposium - International Astronomical Union 140 (1990): 176. http://dx.doi.org/10.1017/s0074180900189880.
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The plasma density fluctuations responsible for interstellar scintillations occur on the same scales as interstellar magnetohydrodynamic waves (Alfvén waves), which are responsible for many important processes such as the acceleration of the cosmic rays. This suggests that these density fluctuations represent a compressive component of MHD waves, and raises the exciting possibility that radioastronomical observations can provide more or less direct measurements of interstellar microphysical processes. Extraction of MHD wave properties from the radio scattering measurements requires a sound theoretical understanding of the relationship between the magnetic field in an MHD wave and the corresponding plasma density perturbation. We present a plasma kinetic theory treatment of the density compression associated with an MHD wave field. The density perturbation may be expressed as the sum of three terms. These terms are proportional to the wave amplitude, wave intensity, and sine transform of the wave intensity, respectively. The coefficients of these three terms are functions of the plasma β, the electron-to-ion temperature ratio, and the angle of wave propagation with respect to the large scale magnetic field. This relation can serve as the basis for inferring the MHD wave field given a radio scattering measurement of the density fluctuation statistics. In an attempt to apply these ideas to the interstellar plasma turbulence, we have made VLBI angular broadening measurements of sources whose lines of sight pass close to supernova remnants. The intensity of MHD waves is expected to be high in the vicinity of the shock waves associated with supernova remnants. We do not yet have unambiguous evidence of enhanced radio wave scattering due to shock-associated MHD waves. However, we have found anomalously high scattering for the source CL4, whose line of sight passes through the Cygnus Loop.
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GRAHAM - SMITH, FRANCIS. „The big ears of radio astronomy“. European Review 10, Nr. 2 (Mai 2002): 285–300. http://dx.doi.org/10.1017/s1062798702000200.
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The special value of radio astronomy lies in the probing of extreme conditions in the universe, including the highest energies and the lowest temperatures. Radio waves can penetrate clouds of gas and dust to reveal objects in the universe and, in particular, in our Galaxy that cannot be seen by visible light. To achieve the highest resolution, radio telescopes in widely separate parts of our globe combine their reception to produce a synthesized image. This is a splendid example of international collaboration. Among the images visualized are pulsars, derived from the remnants of supernovae explosions, and quasar sources powered by black holes.
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Rieu, Nguyen Quang. „Simple Instruments in Radio Astronomy“. Transactions of the International Astronomical Union 24, Nr. 3 (2001): 255–65. http://dx.doi.org/10.1017/s0251107x00000924.
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AbstractRadio astronomy has a major role in the study of the universe. The spiral structure of our Galaxy and the cosmic background radiation were first detected, and the dense component of interstellar gas is studied, at radio wavelengths. COBE revealed very weak temperature fluctuations in the microwave background, considered to be the seeds of galaxies and clusters of galaxies. Most electromagnetic radiation from outer space is absorbed or reflected by the Earth’s atmosphere, except in two narrow spectral windows: the visible-near-infrared and the radio, which are nearly transparent. Centimetre and longer radio waves propagate almost freely in space; observations of them are practically independent of weather. Turbulence in our atmosphere does not distort the wavefront, which simplifies the building of radio telescopes, because no devices are needed to correct for it. Observations at these wavelengths can be made in high atmospheric humidity, or where the sky is not clear enough for optical telescopes.Simple instruments operating at radio wavelengths can be built at low cost in tropical countries, to teach students and to familiarize them with radio astronomy. We describe a two-antennae radio interferometer and a single-dish radio telescope operating at centimetre wavelengths. The Sun and strong synchrotron radio-sources, like Cassiopeia A and Cygnus A, are potential targets.
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Centrella, Joan, Samaya Nissanke und Roy Williams. „Gravitational Waves and Time-Domain Astronomy“. Proceedings of the International Astronomical Union 7, S285 (September 2011): 191–98. http://dx.doi.org/10.1017/s1743921312000592.
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AbstractThe gravitational-wave window onto the universe will open in roughly five years, when Advanced LIGO and Virgo achieve the first detections of high-frequency gravitational waves, most likely coming from compact binary mergers. Electromagnetic follow-up of these triggers, using radio, optical, and high energy telescopes, promises exciting opportunities in multi-messenger time-domain astronomy. In the decade, space-based observations of low-frequency gravitational waves from massive black hole mergers, and their electromagnetic counterparts, will open up further vistas for discovery. This two-part workshop featured brief presentations and stimulating discussions on the challenges and opportunities presented by gravitational-wave astronomy. Highlights from the workshop, with the emphasis on strategies for electromagnetic follow-up, are presented in this report.
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RYABOV, M. I., und L. I. SOBITNIAK. „Tidal phenomena in the Earth’s upper atmosphere“. Astronomical and Astrophysical Transactions, Volume 33, Numéro 1 (01.07.2022): 37–44. http://dx.doi.org/10.17184/eac.6468.
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From 1987 to the present, the radio flux of powerful galactic and extragalactic radio sources is monitored at decameter waves at the URAN-4 radio telescope of the Odessa Observatory of the Radio Astronomy Institute of the National Academy of Sciences of Ukraine. The work is based on revealing the nature of unusual records of radio sources that were not associated with the presence of interference in the decameter radio band. Changes of fluxes of radiation sources at decameter waves are determined by the condition of an ionosphere as a result of variation in space weather and tidal events. When radio sources are observed through a tidal wave, a “plasma lens” effect is realized in the ionosphere. Depending on the position of the radio source relative to the tidal wave, the radiation wave front is sought. As a result, various effects are realized: strong focusing, intense flickering or “blurred” recording of the radio source. This effect was originally reflected in earlier works [1]. In this paper the analog records of radio sources (1987-1990) and digital (1998-2004) are considered and various tidal effects were clarified. Based on the results of measurements, the angular dimensions of the tidal wave, reaching 60 degrees, were determined. Radio astronomy observations in the decameter range at the URAN-4 radio telescope are an effective method for studying tidal phenomena in the Earth's upper atmosphere.
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Wielebinski, R. „The history of polarisation measurements: their role in studies of magnetic fields“. Proceedings of the International Astronomical Union 10, H16 (August 2012): 383. http://dx.doi.org/10.1017/s1743921314011521.
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Radio astronomy gave us new methods to study magnetic fields. Synchrotron radiation, the main cause of comic radio waves, is highly linearly polarised with the ‘E’ vector normal to the magnetic field. The Faraday Effect rotates the ‘E’ vector in thermal regions by the magnetic field in the line of sight. Also the radio Zeeman Effect has been observed.
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Chalmers, Matthew. „Radio waves measure body water“. Physics World 16, Nr. 3 (März 2003): 26–27. http://dx.doi.org/10.1088/2058-7058/16/3/38.
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10
Adawi, I. „Centennial of Hertz’ radio waves“. American Journal of Physics 57, Nr. 2 (Februar 1989): 125–27. http://dx.doi.org/10.1119/1.16106.
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Rucker, H. O., M. Panchenko und C. Weber. „Planetary radio astronomy: Earth, giant planets, and beyond“. Advances in Radio Science 12 (10.11.2014): 211–20. http://dx.doi.org/10.5194/ars-12-211-2014.
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Abstract. The magnetospheric phenomenon of non-thermal radio emission is known since the serendipitous discovery of Jupiter as radio planet in 1955, opening the new field of "Planetary Radio Astronomy". Continuous ground-based observations and, in particular, space-borne measurements have meanwhile produced a comprehensive picture of a fascinating research area. Space missions as the Voyagers to the Giant Planets, specifically Voyager 2 further to Uranus and Neptune, Galileo orbiting Jupiter, and now Cassini in orbit around Saturn since July 2004, provide a huge amount of radio data, well embedded in other experiments monitoring space plasmas and magnetic fields. The present paper as a condensation of a presentation at the Kleinheubacher Tagung 2013 in honour of the 100th anniversary of Prof. Karl Rawer, provides an introduction into the generation mechanism of non-thermal planetary radio waves and highlights some new features of planetary radio emission detected in the recent past. As one of the most sophisticated spacecraft, Cassini, now in space for more than 16 years and still in excellent health, enabled for the first time a seasonal overview of the magnetospheric variations and their implications for the generation of radio emission. Presently most puzzling is the seasonally variable rotational modulation of Saturn kilometric radio emission (SKR) as seen by Cassini, compared with early Voyager observations. The cyclotron maser instability is the fundamental mechanism under which generation and sufficient amplification of non-thermal radio emission is most likely. Considering these physical processes, further theoretical investigations have been started to investigate the conditions and possibilities of non-thermal radio emission from exoplanets, from potential radio planets in extrasolar systems.
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Krafft, C., und A. Volokitin. „Interaction of suprathermal solar wind electron fluxes with sheared whistler waves: fan instability“. Annales Geophysicae 21, Nr. 7 (31.07.2003): 1393–403. http://dx.doi.org/10.5194/angeo-21-1393-2003.
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Abstract. Several in situ measurements performed in the solar wind evidenced that solar type III radio bursts were some-times associated with locally excited Langmuir waves, high-energy electron fluxes and low-frequency electrostatic and electromagnetic waves; moreover, in some cases, the simultaneous identification of energetic electron fluxes, Langmuir and whistler waves was performed. This paper shows how whistlers can be excited in the disturbed solar wind through the so-called "fan instability" by interacting with energetic electrons at the anomalous Doppler resonance. This instability process, which is driven by the anisotropy in the energetic electron velocity distribution along the ambient magnetic field, does not require any positive slope in the suprathermal electron tail and thus can account for physical situations where plateaued reduced electron velocity distributions were observed in solar wind plasmas in association with Langmuir and whistler waves. Owing to linear calculations of growth rates, we show that for disturbed solar wind conditions (that is, when suprathermal particle fluxes propagate along the ambient magnetic field), the fan instability can excite VLF waves (whistlers and lower hybrid waves) with characteristics close to those observed in space experiments.Key words. Space plasma physics (waves and instabilities) – Radio Science (waves in plasma) – Solar physics, astrophysics and astronomy (radio emissions)
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Okuda, Haruyuki, Gunther Hasinger, M. D. Arnaud, S. Bludman, J. Braga, N. Brosch, L. Gurvits et al. „Commission 44: Space & High Energy Astrophysics“. Proceedings of the International Astronomical Union 1, T26A (Dezember 2005): 319–26. http://dx.doi.org/10.1017/s1743921306004777.
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Division XI was born by merging Commission 44 “Space and High Energy Astrophysics” and Commission 48 “High Energy Astrophysics” by the decision at the IAU General Assembly in The Hague (1994). As the naming of space astronomy is technique oriented, i.e. astronomy from space, it covers quite a wide range of astronomy, almost all branches of astronomy are included by the progress of space observations. Historically, it started from high energy astronomy, UV, X, and gamma rays astronomy, somewhat including cosmic ray physics. However, in these days, space observations have expanded to low energy astronomy, such as optical, infrared, submillimeter and even radio waves(Space VLBI).
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Pardo, Juan R., Pierre J. Encrenaz und Daniel Breton. „Utilization of the Radiofrequency Spectrum above 1 GHz by Passive Services“. Symposium - International Astronomical Union 196 (2001): 255–63. http://dx.doi.org/10.1017/s0074180900164174.
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Microwave atmospheric radiometry and radio, mm and sub-mm astronomy are “passive” services, i.e. not involved in any man-made transmission but only concerned with the reception of naturally occurring radio waves. The intensity of the radiation received is not subject to human control, unlike the situation for active services. All active services operate in bands occupied by natural signals of atmospheric and cosmic origin and the active service tranmissions may be powerful enough to noticeably interfere with reception of those signals by scientific services. A conflict exists for the coexistence of active and passive services in many frequency bands, which leads to a need for regulating how to share the electromagnetic spectrum. This document gives an overview of the problems of frequency sharing in the longwave region of the electromagnetic spectrum (radio to submillimetre waves).
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Cartlidge, Edwin. „Radio offers view of gravitational waves“. Physics World 34, Nr. 2 (01.05.2021): 5. http://dx.doi.org/10.1088/2058-7058/34/02/05.
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Day, Charles. „Resonant radio waves rotate tokamak plasma“. Physics Today 62, Nr. 6 (Juni 2009): 18–19. http://dx.doi.org/10.1063/1.3156321.
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Chernov, Gennady, und Valery Fomichev. „On the Issue of the Origin of Type II Solar Radio Bursts“. Astrophysical Journal 922, Nr. 1 (01.11.2021): 82. http://dx.doi.org/10.3847/1538-4357/ac1f32.
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Abstract Type II solar radio bursts are among the most powerful events in the solar radio emission in the meter wavelength range. It is generally accepted that the agents generating type II radio bursts are magnetohydrodynamic shock waves. But the relationship between the shock waves and the other manifestations of the large-scale disturbances in the solar atmosphere (coronal mass ejections, Morton waves, EUW waves) remains unclear. To clarify a problem, it is important to determine the conditions of generation of type II radio bursts. Here, the model of the radio source is based on the generation of radio emission within the front of the collisionless shock wave where the Buneman instability of plasma waves is developed. In the frame of this model, the Alfvén magnetic Mach number must exceed the critical value, and there is a strict restriction on the perpendicularity of the front. The model allows us to obtain the information about the parameters of the shock waves and the parameters of the medium by the parameters of type II bursts. The estimates, obtained in this paper for several events with the band splitting of the fundamental and harmonic emission bands of the type II bursts, confirm the necessary conditions of the model. In this case the registration of type II radio bursts is an indication of the propagation of shock waves in the solar atmosphere, and the absence of type II radio bursts is not an indication of the absence of shock waves. Such a situation should be taken into account when investigating the relationship between type II radio bursts and other manifestations of solar activity.
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Mann, G., C. Vocks und A. Warmuth. „Type III radio bursts and excitation of Langmuir waves by energetic electrons“. Astronomy & Astrophysics 660 (April 2022): A91. http://dx.doi.org/10.1051/0004-6361/202142804.
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Context. Solar activity occurs not only in terms of the well-known 11-year Sun spot cycle but also in terms of short-lived phenomena as radio bursts. For instance, type III radio bursts are the most common phenomenon of this activity in the Sun’s radio radiation. In dynamic radio spectra, they appear as short-lived stripes of enhanced radio emission rapidly drifting from high to low frequencies. They are regarded as the radio signature of beams of energetic electrons travelling along magnetic field lines in the corona. The radio emission is thought to be plasma emission, that is to say the radio emission happens near the electron plasma frequency and/or its harmonics. Plasma emission means, that energetic electrons excite Langmuir waves, which convert into radio waves. Aims. Initially, energetic electrons are injected in a small region in the corona. Due to their spatio-temporal evolution, they develop a beam-like velocity distribution function (VDF), which is able to excite Langmuir waves. The aim of the paper is to study the spatio-temporal behaviour of the generation of Langmuir waves under coronal cirumstances and its effect on type III radio bursts. Methods. The generation of Langmuir waves is treated by means of the Maxwell-Vlasov equations. The results are discussed by employing plasma parameters usually found in the corona, for instance at the 150 MHz level. Results. The Langmuir waves associated with the type III bursts are not generated by a monoenergetic electron beam, but by a population of energetic electrons with a broad velocity distribution. Hence, the Langmuir waves are produced by different parts of the energetic electron population at different times and positions. Conclusions. In the case of type III bursts, the velocities derived from their drift rates in dynamic radio spectra are not the velocities of electrons, which generate the onset of the type III burst at a given frequency. That can lead to an apparent accelerated motion of the type III radio burst source.
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Delbourgo, Robert, und Peter M. McCulloch. „Graeme Reade Anthony (‘Bill’) Ellis 1921–2011“. Historical Records of Australian Science 24, Nr. 1 (2013): 96. http://dx.doi.org/10.1071/hr12020.
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Graeme Reade Anthony Ellis (universally known as ?Bill') was a pioneer in the area of low-frequency radio observations. By exploiting Hobart's geomagnetic latitude and the lack of background radio noise there, he was able to make major discoveries at these low frequencies (principally in the frequency range 1?10�MHz).Among the questions he pursuedwere the propagation/dispersion/reflection of radio waves in the ionosphere and the detection of radio emissions from the Sun, the galactic disk and Jupiter. He built innovative radio receivers and de-dispersers to gain information about the radio sources, for example about the Sun via aurorae and about the influence of Io on the Jovian emissions. It is thanks to Ellis' practical research investigations and clever experimental methods that radio astronomy at the University of Tasmania is today firmly established and internationally recognized.
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Samoylov, A. G., V. S. Samoylov und S. A. X. Nasir. „Loss of radio waves energy on radio lines satellite-earth station“. Journal of Physics: Conference Series 2094, Nr. 4 (01.11.2021): 042080. http://dx.doi.org/10.1088/1742-6596/2094/4/042080.
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Abstract The main contribution of this paper is to study the influence of various natural factors on the conditions for the radio signals propagation on the satellite - Earth links. It is shown that the ionosphere practically does not interfere with satellite radio communications at frequencies above 5 GHz. The mathematical model is proposed for the numerical determination of the attenuation of the radio signal depending on the optical visibility during dust storms along the communication path.
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Mann, G., C. Vocks, A. Warmuth, J. Magdalenic, M. Bisi, E. Carley, B. Dabrowski et al. „Excitation of Langmuir waves at shocks and solar type II radio bursts“. Astronomy & Astrophysics 660 (April 2022): A71. http://dx.doi.org/10.1051/0004-6361/202142201.
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Context. In the solar corona, shocks can be generated due to the pressure pulse of a flare and/or driven by a rising coronal mass ejection (CME). Coronal shock waves can be observed as solar type II radio bursts in the Sun’s radio radiation. In dynamic radio spectra, they appear as stripes of an enhanced radio emission slowly drifting from high to low frequencies. The radio emission is thought to be plasma emission, that is to say the emission happens near the electron plasma frequency and/or its harmonics. Plasma emission means that energetic electrons excite Langmuir waves, which convert into radio waves via non-linear plasma processes. Thus, energetic electrons are necessary for plasma emission. In the case of type II radio bursts, the energetic electrons are considered to be shock accelerated. Aims. Shock drift acceleration (SDA) is regarded as the mechanism for producing energetic electrons in the foreshock region. SDA delivers a shifted loss-cone velocity distribution function (VDF) for the energetic electrons. The aim of the paper is to study in which way and under which conditions a shifted loss-cone VDF of electrons excites Langmuir waves in an efficient way in the corona. Methods. By means of the results of SDA, the shape of the resulted VDF was derived. It is a shifted loss-cone VDF showing both a loss-cone and a beam-like component. The growth rates for exciting Langmuir waves were calculated in the framework of Maxwell-Vlasov equations. The results are discussed by employing plasma and shock parameters usually found in the corona at the 25 MHz level. Results. We have found that moderate coronal shocks with an Alfven-Mach number in the range 1.59 < MA < 2.53 are able to accelerate electrons up to energies sufficient enough to excite Langmur waves, which convert into radio waves seen as solar type II radio bursts.
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Kim, D. Ch, E. T. Ageeva, N. T. Afanasiev, S. O. Chudaev, I. G. Makhro und O. I. Medvedeva. „Numerical-analytical method for calculating the refraction of radio waves in a chaotic upper atmosphere“. Canadian Journal of Physics 99, Nr. 9 (September 2021): 772–77. http://dx.doi.org/10.1139/cjp-2020-0334.
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An operational method is proposed for calculating the refraction of decameter radio waves in a randomly-inhomogeneous upper atmosphere. The method is based on the numerical-analytical solution of stochastic equations of geometric optics. An integral expression is obtained for the dispersion of the refraction angle of a radio wave on the atmospheric path using the approximation of the perturbation method. For a quick calculation of the statistical moment of the refraction angle, the integral expression is reduced to an ordinary first-order differential equation. Joint numerical solution of the unperturbed ray equations and the equations for the statistical moment allows an operational estimate of beam width of radio waves arriving at the observation point. The results of numerical calculations of the standard deviations of the refraction angles of radio waves on paths of various lengths are presented.
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Miller, Johanna. „Radio waves map matter without counting galaxies“. Physics Today 63, Nr. 9 (September 2010): 15–19. http://dx.doi.org/10.1063/1.3490487.
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Jarman, Sam. „Simulation shows Great Pyramid focuses radio waves“. Physics World 31, Nr. 9 (September 2018): 4. http://dx.doi.org/10.1088/2058-7058/31/9/6.
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Stanislavsky, A., A. Koval, I. Bubnov und A. Brazhenko. „Stanislavsky, A.A., Koval, A.A., Bubnov, I.N., and Brazhenko, A.I. Progress in the study of decameter-wave- length solar radio emission with Ukrainian radio telescopes. Part 2. (Invited paper)“. RADIO PHYSICS AND RADIO ASTRONOMY 28, Nr. 3 (2023): 183–200. http://dx.doi.org/10.15407/rpra28.03.183.
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Subject and Purpose. This part of the paper continues presentation of results of the solar radio emission studies performed with Ukrainian radio telescopes over the past 20 years. The importance is stressed of developing adequate instruments and methods for identifying the nature of decameter-wavelength radio emissions from the Sun. Methods and Methodology. The low frequency Ukrainian radio telescopes UTR-2, GURT and URAN-2 have been used in the project along with other ground- and space based instruments in order to achieve a comprehensive understanding of physical conditions in the solar corona. Results. Special methods and tools have been developed for studying radio frequency burst emissions against the background of strong interference. Unique data have been obtained concerning sources of sporadic radio emissions from the Sun, as well as the contribution from wave propagation effects and the impact of the ionosphere on the results of observations. The most significant observational and theoretical results are presented, obtained in the study of solar low frequency emissions over the past 20 years. Solar radio emissions are shown to be efficient sounding signals not for the solar corona alone but for the Earth’s ionosphere as well, which allows identifying its impact on the results of radio astronomy observations. Conclusions. The Ukrainian radio telescopes of the meter and decameter wavebands currently are unrivalled tools for investigating the Universe in the low-frequency range of radio waves. Owing to their advanced characteristics, they make a significant contribution to the progress of world’s solar radio astronomy.
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Kumar, Pawan, und Željka Bošnjak. „FRB coherent emission from decay of Alfvén waves“. Monthly Notices of the Royal Astronomical Society 494, Nr. 2 (20.03.2020): 2385–95. http://dx.doi.org/10.1093/mnras/staa774.
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ABSTRACT We present a model for fast radio bursts (FRBs) where a large-amplitude Alfvén wave packet is launched by a disturbance near the surface of a magnetar, and a substantial fraction of the wave energy is converted to coherent radio waves at a distance of a few tens of neutron star radii. The wave amplitude at the magnetar surface should be about 1011 G in order to produce an FRB of isotropic luminosity 1044 erg s−1. An electric current along the static magnetic field is required by Alfvén waves with non-zero component of transverse wave vector. The current is supplied by counter-streaming electron–positron pairs, which have to move at nearly the speed of light at larger radii as the plasma density decreases with distance from the magnetar surface. The counter-streaming pairs are subject to two-stream instability, which leads to formation of particle bunches of size of the order of c/ωp, where ωp is the plasma frequency. A strong electric field develops along the static magnetic field when the wave packet arrives at a radius where electron–positron density is insufficient to supply the current required by the wave. The electric field accelerates particle bunches along the curved magnetic field lines, and that produces the coherent FRB radiation. We provide a number of predictions of this model.
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Wang, Yu, Haiyan Zhang, Jian Wang, Shijie Huang, Hao Hu und Cheng Yang. „A Software for RFI Analysis of Radio Environment around Radio Telescope“. Universe 9, Nr. 6 (08.06.2023): 277. http://dx.doi.org/10.3390/universe9060277.
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Radio astronomy uses radio telescopes to detect very faint emissions from celestial objects. However, human-made radio frequency interference (RFI) is currently a common problem faced by most terrestrial radio telescopes, and it is getting worse with the development of the economy and technology. Therefore, it is essential to monitor and evaluate interference during the planning, construction, and operation stages of the radio telescope and protect the quiet radio environment around the radio astronomical site. In this paper, we present a software for an RFI analysis of the radio environment around the telescope. In this software, information has been collected, including the location of the site; the technical specifications, such as aperture and the frequency range of the radio telescopes; and the terrain around the site. The software and its modules are composed of telescope, geographic, and meteorological databases, and analysis modules of terrestrial and space-based RFI. Combined with the propagation characteristics of radio waves, we can analyze and evaluate RFI on the ground and in space around the radio telescope. The feasibility of the software has been proved by the experimental implementation of the propagation properties and RFI source estimation. With this software, efficient technical support can be expected for protecting the radio environment around the telescope, as well as improving site selection for planned radio astronomical facilities.
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Rybarczyk, R. Joseph, Alexandria E. D. Federick, Oleksandr Kokhan, Ryan Luckay und Giovanna Scarel. „Probing electromagnetic wave energy with an in-series assembly of thermoelectric devices“. AIP Advances 12, Nr. 4 (01.04.2022): 045201. http://dx.doi.org/10.1063/5.0082749.
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We study the interaction of radio waves, microwaves, and infrared laser light of power P and period τ with a macroscopic thermoelectric (TEC) device-based detector and probe the energy Pτ as being the energy of these electromagnetic (EM) waves. Our detectors are in-series assemblies of TEC devices. We treat these detectors as equivalent to capacitors and/or inductors. The energy Pτ enables characterizing detector’s parameters, such as equivalent capacitance, inductance, resistance, responsivities, effective power, and efficiency. Through various scaling procedures, Pτ also aids in determining the power P of the EM waves. We compare the performance of our detectors with that of other TEC devices and with radio- and microwave-sensitive devices reported in the current literature, such as spin–orbit torque and spin–torque oscillator devices, heterojunction backward tunnel diodes, and Schottky diodes. We observe that the performance of our detectors is inferior. However, the order of magnitude of our detector’s parameters is in reasonable agreement with those of other TEC and non-TEC devices. We conclude that TEC devices can be used to detect radio waves and that Pτ effectively captures the energy of the EM waves. Considering Pτ as the EM wave’s energy offers a classical approach to the interaction of EM waves with matter in which photons are not involved. With the EM wave’s energy depending upon two variables (P and τ), a similar response could be produced by, e.g., radio waves and visible light, leading to interesting consequences that we briefly outline.
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Gancio, G., C. O. Lousto, L. Combi, S. del Palacio, F. G. López Armengol, J. A. Combi, F. García et al. „Upgraded antennas for pulsar observations in the Argentine Institute of Radio astronomy“. Astronomy & Astrophysics 633 (Januar 2020): A84. http://dx.doi.org/10.1051/0004-6361/201936525.
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Context. The Argentine Institute of Radio astronomy (IAR) is equipped with two single-dish 30 m radio antennas capable of performing daily observations of pulsars and radio transients in the southern hemisphere at 1.4 GHz. Aims. We aim to introduce to the international community the upgrades performed and to show that the IAR observatory has become suitable for investigations in numerous areas of pulsar radio astronomy, such as pulsar timing arrays, targeted searches of continuous gravitational waves sources, monitoring of magnetars and glitching pulsars, and studies of a short time scale interstellar scintillation. Methods. We refurbished the two antennas at IAR to achieve high-quality timing observations. We gathered more than 1000 h of observations with both antennas in order to study the timing precision and sensitivity they can achieve. Results. We introduce the new developments for both radio telescopes at IAR. We present daily observations of the millisecond pulsar J0437−4715 with timing precision better than 1 μs. We also present a follow-up of the reactivation of the magnetar XTE J1810–197 and the measurement and monitoring of the latest (Feb. 1, 2019) glitch of the Vela pulsar (J0835–4510). Conclusions. We show that IAR is capable of performing pulsar monitoring in the 1.4 GHz radio band for long periods of time with a daily cadence. This opens up the possibility of pursuing several goals in pulsar science, including coordinated multi-wavelength observations with other observatories. In particular, daily observations of the millisecond pulsar J0437−4715 would increase the sensitivity of pulsar timing arrays. We also show IAR’s great potential for studying targets of opportunity and transient phenomena, such as magnetars, glitches, and fast-radio-burst sources.
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Stepkin, S. V., O. O. Konovalenko, Y. V. Vasylkivskyi und D. V. Mukha. „INTERSTELLAR MEDIUM AND DECAMETER RADIO SPECTROSCOPY“. Radio physics and radio astronomy 26, Nr. 4 (24.11.2021): 314–25. http://dx.doi.org/10.15407/rpra26.04.314.
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Purpose: The analytical review of the main results of research in the new direction of the low-frequency radio astronomy, the interstellar medium radio spectroscopy at decameter waves, which had led to astrophysical discovery, recording of the radio recombination lines in absorption for highly excited states of interstellar carbon atoms (more than 600). Design/methodology/approach: The UTR-2 world-largest broadband radio telescope of decameter waves optimally connected with the digital correlation spectrum analyzers has been used. Continuous modernization of antenna system and devices allowed increasing the analysis band from 100 kHzto 24 MHz and a number of channels from 32 to 8192. The radio telescope and receiving equipment with appropriate software allowed to have a long efficient integration time enough for a large line series simultaneously with high resolution, noise immunity and relative sensitivity. Findings: A new type of interstellar spectral lines has been discovered and studied, the interstellar carbon radio recombination lines in absorption for the record high excited atoms with principal quantum numbers greater than 1000. The line parameters (intensity, shape, width, radial velocity) and their relation ship with the interstellar medium physical parameters have been determined. The temperature of line forming regions is about 100 K, the electron concentration up to 0.1 cm–3 and the size of a line forming region is about 10 pc. For the first time, radio recombination lines were observed in absorption. They have significant broadening and are amplified by the dielectronic-like recombination mechanism and are also the lowest frequency lines in atomic spectroscopy. Conclusions: The detected low-frequency carbon radio recombination lines and their observations have become a new highly effective tool for the cold partially ionized interstellar plasma diagnostics. Using them allows obtaining the information which is not available with the other astrophysical methods. For almost half a century of their research, a large amount of hardware-methodical and astrophysical results have been obtained including a record number of Galaxy objects, where there levant lines have been recorded. The domestic achievements have stimulated many theoretical and experimental studies in other countries, but the scientific achievements of Ukrainian scientists prove the best prospects for further development of this very important area of astronomical science. Key words: low-frequency radio astronomy; radio telescope; interstellar medium; radio recombination lines; carbon; hydrogen; spectral analyzer
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Bubukin, I. T., I. V. Rakut, M. I. Agafonov, A. A. Yablokov, A. L. Pankratov, T. Yu Gorbunova und R. V. Gorbunov. „Comparative Analysis of the Propagation Conditions of Millimeter Radio Waves at Radio Astronomy Polygons in Russia and Uzbekistan“. Astronomy Reports 65, Nr. 7 (Juli 2021): 598–614. http://dx.doi.org/10.1134/s1063772921080011.
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Kazbegi, AZ, GZ Machabeli und G. Melikidze. „Radio Emission Model of a 'Typical' Pulsar“. Australian Journal of Physics 40, Nr. 6 (1987): 755. http://dx.doi.org/10.1071/ph870755.
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The generation of radio waves in the plasma of the pulsar magnetosphere is considered taking into account the inhomogeneity of the dipole magnetic field. It is shown that the growth rate of the instability of the electromagnetic waves calculated in the non-resonance case turns out to be of the order of 1/ TO (where TO is the time of plasma escape from the light cylinder). However, the generation of electromagnetic waves from a new type Cherenkov resonance is possible, occurring when the particles have transverse velocities caused by the drift due to the inhomogeneity of the magnetic field. Estimates show that the development of this type of instability is possible only for pulsars with ages which exceed 104 yr. We make an attempt to explain some peculiarities of 'typical' pulsar emission on the basis of the model developed.
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Fulara, Aarti, und Ryun-Young Kwon. „Global Nature of Solar Coronal Shock Waves Shown by Inconsistency between EUV Waves and Type II Radio Bursts“. Astrophysical Journal Letters 919, Nr. 1 (01.09.2021): L7. http://dx.doi.org/10.3847/2041-8213/ac230d.
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Abstract We re-examine the physical relationship between extreme ultraviolet (EUV) waves and type II radio bursts. It has been thought that they are two observational aspects of a single coronal shock wave. However, a lack of their speed correlation hampers the understanding of their respective (or common) natures in a single phenomenon. Knowing the uncertainties in identifying true wave components from observations and measuring their speeds, we re-examine the speeds of EUV waves reported in previous literature and compare these with type II radio bursts and coronal mass ejections (CMEs). This confirms the inconsistency between the speeds of EUV waves and their associated type II radio bursts. Second, CME speeds are found to have a better correlation with type II radio bursts than EUV waves. Finally, type II speeds and their range tend to be much greater than those of EUV waves. We demonstrate that the speed inconsistency is in fact an intrinsic tendency and elucidate the nature of a coronal shock wave consisting of both driven and non-driven parts. This suggests that the speed inconsistency would remain even if all other uncertainties were removed.
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Dobie, Dougal, Tara Murphy, David L. Kaplan, Kenta Hotokezaka, Juan Pablo Bonilla Ataides, Elizabeth K. Mahony und Elaine M. Sadler. „Radio afterglows from compact binary coalescences: prospects for next-generation telescopes“. Monthly Notices of the Royal Astronomical Society 505, Nr. 2 (22.05.2021): 2647–61. http://dx.doi.org/10.1093/mnras/stab1468.
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ABSTRACT The detection of gravitational waves from a neutron star merger, GW170817, marked the dawn of a new era in time-domain astronomy. Monitoring of the radio emission produced by the merger, including high-resolution radio imaging, enabled measurements of merger properties including the energetics and inclination angle. In this work, we compare the capabilities of current and future gravitational wave facilities to the sensitivity of radio facilities to quantify the prospects for detecting the radio afterglows of gravitational wave events. We consider three observing strategies to identify future mergers – wide field follow-up, targeting galaxies within the merger localization and deep monitoring of known counterparts. We find that while planned radio facilities like the Square Kilometre Array will be capable of detecting mergers at gigaparsec distances, no facilities are sufficiently sensitive to detect mergers at the range of proposed third-generation gravitational wave detectors that would operate starting in the 2030s.
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Izmaïlov, G. N., und V. V. Ozolin. „Including precision clocks into space-based net as gravitational antennas“. Journal of Physics: Conference Series 2081, Nr. 1 (01.11.2021): 012021. http://dx.doi.org/10.1088/1742-6596/2081/1/012021.
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Abstract Here we propose to use a precision clock in a space-based ultra-precise clock network to register sources of low-frequency gravitational waves of cosmic origin in the range of 10-3 ÷ 0.1 Hz. We also show that the method of comparing clocks at inland and intercontinental distances (very long baseline interferometry), originally developed for radio astronomy and geodesy, can be used as a prototype method for recording gravitational waves. Estimates of the measurement accuracy are given. An analyse of precise clocks possibilities for experimental estimates for rotation parameter of Gödel universe and GW recordings is offered, which in particular opens up the prospect of registering circularly polarized gravitational waves. Some new problems of small time intervals registration from general relativity, thermodynamics and quantum mechanics points of view are discussed.
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An, Haipeng, Shuailiang Ge und Jia Liu. „Solar Radio Emissions and Ultralight Dark Matter“. Universe 9, Nr. 3 (07.03.2023): 142. http://dx.doi.org/10.3390/universe9030142.
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Ultralight axions and dark photons are well-motivated dark matter candidates. Inside the plasma, once the mass of ultralight dark matter candidates equals the plasma frequency, they can resonantly convert into electromagnetic waves, due to the coupling between the ultralight dark matter particles and the standard model photons. The converted electromagnetic waves are monochromatic. In this article, we review the development of using radio detectors to search for ultralight dark matter conversions in the solar corona and solar wind plasma.
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Pleukhov, A. N. „Nonreciprocity of radio waves in a meteor radio channel“. Radiophysics and Quantum Electronics 31, Nr. 5 (Mai 1988): 395–99. http://dx.doi.org/10.1007/bf01043601.
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Dupuis, Réjean J., und the LIGO Scientific collaboration. „Targeted searches for gravitational waves from radio pulsars“. Journal of Physics: Conference Series 32 (02.03.2006): 52–57. http://dx.doi.org/10.1088/1742-6596/32/1/009.
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Sishtla, Chaitanya Prasad, Immanuel Christopher Jebaraj, Jens Pomoell, Norbert Magyar, Marc Pulupa, Emilia Kilpua und Stuart D. Bale. „The Effect of the Parametric Decay Instability on the Morphology of Coronal Type III Radio Bursts“. Astrophysical Journal Letters 959, Nr. 2 (01.12.2023): L33. http://dx.doi.org/10.3847/2041-8213/ad137e.
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Abstract The nonlinear evolution of Alfvén waves in the solar corona leads to the generation of Alfvénic turbulence. This description of the Alfvén waves involves parametric instabilities where the parent wave decays into slow mode waves giving rise to density fluctuations. These density fluctuations, in turn, play a crucial role in the modulation of the dynamic spectrum of type III radio bursts, which are observed at the fundamental of local plasma frequency and are sensitive to the local density. During observations of such radio bursts, fine structures are detected across different temporal ranges. In this study, we examine density fluctuations generated through the parametric decay instability (PDI) of Alfvén waves as a mechanism to generate striations in the dynamic spectrum of type III radio bursts using magnetohydrodynamic simulations of the solar corona. An Alfvén wave is injected into the quiet solar wind by perturbing the transverse magnetic field and velocity components, which subsequently undergo the PDI instability. The type III burst is modeled as a fast-moving radiation source that samples the background solar wind as it propagates to emit radio waves. We find the simulated dynamic spectrum to contain striations directly affected by the multiscale density fluctuations in the wind.
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Golbraikh, Ephim, und Yuri Lyubarsky. „On the Escape of Low-frequency Waves from Magnetospheres of Neutron Stars“. Astrophysical Journal 957, Nr. 2 (01.11.2023): 102. http://dx.doi.org/10.3847/1538-4357/acfa78.
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Abstract We study the nonlinear decay of the fast magnetosonic (fms) into the Alfvén waves in relativistic force-free magnetohydrodynamics. The work has been motivated by models of pulsar radio emission and fast radio bursts (FRBs), in which the emission is generated in neutron star magnetospheres at conditions when not only the Larmor but also the plasma frequencies significantly exceed the radiation frequency. The decay process places limits on the source luminosity in these models. We estimated the decay rate and showed that the phase volume of Alfvén waves available for the decay of an fms wave is infinite. Therefore, the energy of fms waves could be completely transferred to the small-scale Alfvén waves not via a cascade, as in the Kolmogorov turbulence, but directly. Our results explain the anomalously low radio efficiency of the Crab pulsar and show that FRBs could not be produced well within magnetar magnetospheres.
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Galeano, David, und A. Quintero Edwin. „Monitoring the brightness temperature of the Moon throughout the lunar cycle from radio observations in the Ku band“. Journal of Physics: Conference Series 2090, Nr. 1 (01.11.2021): 012159. http://dx.doi.org/10.1088/1742-6596/2090/1/012159.
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Abstract Within the spectrum of radio waves, the Ku band (12 - 18 GHz ) stands out for the wide range of instruments available and for its relative ease of acquisition, given that satellite television operates in this band. This situation offers a great opportunity for the development of radio astronomy in countries with unfavorable climatic conditions for optical astronomy, since this band is only affected by dense masses of water vapor. In this article we present a methodology for the calibration of the receiver system of compact Ku-band radio telescopes, and its application in the determination of the brightness temperature of the Moon. Our methodology involves modeling the influence of the atmosphere of the Earth on the response of the radioreceptor, which minimizes the error in the calculation of the brightness temperature of the observed object. We applied the proposed methodology in the monitoring of the Lunar cycle using the Ku-band radio telescope of the Observatorio Astronomico of Universidad Tecnológica de Pereira, Colombia (OAUTP). After observing during May, June, and July of 2021, we obtained an average temperature of 213.15 K, with maximum and minimum values of 275.55 K and 150.75 K, respectively. In addition, we evidenced a delay of 5.75 days between the phase in which the maximum temperature is presented and the phase of the full Moon, which is consistent with the frequency of observation. The results show that our methodology is useful to optimize the calibration of compact Ku-band radio telescopes, and expand the potential of this type of instrument for the scientific study of radio sources other than the Sun, in this case the Moon.
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Aqasha, Adam, Andrien Zheng, Sneha Athreya und Hoe Teck Tan. „Investigation of the Sudden Solar Ionospheric Disturbance using Radio Telescope“. EPJ Web of Conferences 240 (2020): 07003. http://dx.doi.org/10.1051/epjconf/202024007003.
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Low-frequency radio telescopes are cheap and useful devices for the investigation of terrestrial and extra-terrestrial emissions. These emissions come either from the Sun and the planet Jupiter to terrestrial emissions. This project aims to investigate the Very Low Frequency (VLF) waves from mid-August to October 2019 using Radio JOVE (20 MHz) and SSID (3-30 kHz) to observe for the occurrence of solar flares and see how if the radio telescopes that the team set up is reliable. This will allow us future students aspiring to learn about astronomy to examine solar flares in detail during the upcoming solar maximum. Not many flares were detected as this period happens to be a solar minimum. However, a series of flares occurred between 30 September 2019 and 1 October 2019, which the telescopes have been able to detect, particularly SSID.
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Chan, Man. „Radio Constraints of Dark Matter: A Review and Some Future Perspectives“. Galaxies 9, Nr. 1 (28.01.2021): 11. http://dx.doi.org/10.3390/galaxies9010011.
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In the past few decades, many studies have analyzed the data of gamma-rays, X-rays, radio waves, electrons, positrons, anti-protons, and neutrinos to search for the signal of dark matter annihilation. In particular, analyzing radio data has been one of the most important and effective ways to constrain dark matter. In this article, we review the physics and the theoretical framework of using radio data to constrain annihilating dark matter. We also review some important radio constraints of annihilating dark matter and discuss the future perspectives of using radio detection to reveal the nature of dark matter.
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Fedorenko, V. N. „Acceleration of particles by shock waves in radio galaxies“. Astrophysics 28, Nr. 1 (1988): 71–75. http://dx.doi.org/10.1007/bf01014851.
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Forte, Biagio, Richard A. Fallows, Mario M. Bisi, Jinge Zhang, Andrzej Krankowski, Bartosz Dabrowski, Hanna Rothkaehl und Christian Vocks. „Interpretation of Radio Wave Scintillation Observed through LOFAR Radio Telescopes“. Astrophysical Journal Supplement Series 263, Nr. 2 (01.12.2022): 36. http://dx.doi.org/10.3847/1538-4365/ac6deb.
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Abstract Radio waves propagating through a medium containing irregularities in the spatial distribution of the electron density develop fluctuations in their intensities and phases. In the case of radio waves emitted from astronomical objects, they propagate through electron density irregularities in the interstellar medium, the interplanetary medium, and Earth’s ionosphere. The LOFAR radio telescope, with stations across Europe, can measure intensity across the VHF radio band and thus intensity scintillation on the signals received from compact astronomical objects. Modeling intensity scintillation allows the estimate of various parameters of the propagation medium, for example, its drift velocity and its turbulent power spectrum. However, these estimates are based on the assumptions of ergodicity of the observed intensity fluctuations and, typically, of weak scattering. A case study of single-station LOFAR observations of the strong astronomical source Cassiopeia A in the VHF range is utilized to illustrate deviations from ergodicity, as well as the presence of both weak and strong scattering. Here it is demonstrated how these aspects can lead to misleading estimates of the propagation medium properties, for example, in the solar wind. This analysis provides a method to model errors in these estimates, which can be used in the characterization of both the interplanetary medium and Earth’s ionosphere. Although the discussion is limited to the case of the interplanetary medium and Earth’s ionosphere, its ideas are also applicable to the case of the interstellar medium.
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Robinson, T. R. „The role of natural E-region plasma turbulence in the enhanced absorption of HF radio waves in the auroral ionosphere:Implications for RF heating of the auroral electrojet“. Annales Geophysicae 12, Nr. 4 (31.03.1994): 316–32. http://dx.doi.org/10.1007/s00585-994-0316-9.
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Abstract. Physical processes which affect the absorption of radio waves passing through the auroral E-region when Farley-Buneman irregularities are present are examined. In particular, the question of whether or not it is legitimate to include the anomalous wave-enhanced collision frequency, which has been used successfully to account for the heating effects of Farley-Buneman waves in the auroral E-region, in the usual expression for the radio-wave absorption coefficient is addressed. Effects also considered are those due to wave coupling between electromagnetic waves and high-frequency electrostatic waves in the presence of Farley-Buneman irregularities. The implications for radio-wave heating of the auroral electrojet of these processes are also discussed. In particular, a new theoretical model for calculating the effects of high-power radio-wave heating on the electron temperature in an electrojet containing Farley-Buneman turbulence is presented.
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Maksimovic, M., S. D. Bale, T. Chust, Y. Khotyaintsev, V. Krasnoselskikh, M. Kretzschmar, D. Plettemeier et al. „The Solar Orbiter Radio and Plasma Waves (RPW) instrument“. Astronomy & Astrophysics 642 (30.09.2020): A12. http://dx.doi.org/10.1051/0004-6361/201936214.
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The Radio and Plasma Waves (RPW) instrument on the ESA Solar Orbiter mission is described in this paper. This instrument is designed to measure in-situ magnetic and electric fields and waves from the continuous to a few hundreds of kHz. RPW will also observe solar radio emissions up to 16 MHz. The RPW instrument is of primary importance to the Solar Orbiter mission and science requirements since it is essential to answer three of the four mission overarching science objectives. In addition RPW will exchange on-board data with the other in-situ instruments in order to process algorithms for interplanetary shocks and type III langmuir waves detections.
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Chattopadhyay, Debatri, Simon Stevenson, Jarrod R. Hurley, Luca J. Rossi und Chris Flynn. „Modelling double neutron stars: radio and gravitational waves“. Monthly Notices of the Royal Astronomical Society 494, Nr. 2 (19.03.2020): 1587–610. http://dx.doi.org/10.1093/mnras/staa756.
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ABSTRACT We have implemented prescriptions for modelling pulsars in the rapid binary population synthesis code Compact Object Mergers: Population Astrophysics and Statistics. We perform a detailed analysis of the double neutron star (DNS) population, accounting for radio survey selection effects. The surface magnetic field decay time-scale (∼1000 Myr) and mass-scale (∼0.02 M⊙) are the dominant uncertainties in our model. Mass accretion during common envelope evolution plays a non-trivial role in recycling pulsars. We find a best-fitting model that is in broad agreement with the observed Galactic DNS population. Though the pulsar parameters (period and period derivative) are strongly biased by radio selection effects, the observed orbital parameters (orbital period and eccentricity) closely represent the intrinsic distributions. The number of radio observable DNSs in the Milky Way at present is about 2500 in our model, corresponding to approximately 10 per cent of the predicted total number of DNSs in the Galaxy. Using our model calibrated to the Galactic DNS population, we make predictions for DNS mergers observed in gravitational waves. The DNS chirp mass distribution varies from 1.1 to 2.1 M⊙ and the median is found to be 1.14 M⊙. The expected effective spin χeff for isolated DNSs is ≲0.03 from our model. We predict that 34 per cent of the current Galactic isolated DNSs will merge within a Hubble time, and have a median total mass of 2.7 M⊙. Finally, we discuss implications for fast radio bursts and post-merger remnant gravitational waves.
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Bryantsev, V. F. „Antipodal propagation of decameter radio waves“. Radiophysics and Quantum Electronics 55, Nr. 9 (Februar 2013): 539–45. http://dx.doi.org/10.1007/s11141-013-9390-8.
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Fakir, Redouane. „The Interstellar Medium as a Gravity Wave Detector“. International Journal of Modern Physics D 06, Nr. 01 (Februar 1997): 49–56. http://dx.doi.org/10.1142/s0218271897000042.
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An observer, situated several thousand light-years away from a radio pulsar, finds himself embedded in the diffraction pattern resulting from the propagation of the radio waves through the irregular interstellar medium. The gravity waves produced by an intervening binary star cause the diffraction pattern to be displaced laterally in a manner familiar from refractive interstellar scintillation, except that this gravity wave effect is not dispersive. This periodic displacement can reach a few hundred kilometers. Thus, there seems to be a possibility that the exceedingly faint gravity waves can manifest themselves macroscopically.