Hyperfine Polarization Structure of Jupiter’s Radio Bursts

1976 ◽  
Vol 3 (1) ◽  
pp. 49-51 ◽  
Author(s):  
P. S. Whitham
Keyword(s):  
Fine Structure ◽  
Radio Emission ◽  
Preliminary Report ◽  
Low Frequency ◽  
Incident Radiation ◽  
Radio Bursts ◽  
Polarization Structure ◽  
Yield Information ◽  
Linearly Polarized ◽  
Elliptically Polarized

Observations of Jupiter’s decametric radio burst have established that above 20 MHz more than 90% of the emission is elliptically polarized in the RH sense, but below this frequency the proportion of the LH polarization increases (Sherrill 1965) until at 10 MHz nearly 40% of the emission is LH polarized (Dowden 1963). The best time and frequency resolutions so far obtained when examining the polarization of the spectra of Jupiter’s bursts have been 10 ms and 50 kHz respectively (Gordon and Warwick 1967, Riihimaa 1975). To study the fine structure of Jupiter’s emission as observed by the linearly polarized Llanherne low frequency radio telescope (Ellis 1972), spectrum analysers with resolutions in the ranges 0.3 — 1 msec and 2–10 kHz have been used (Ellis 1973a, 1973b, 1974, 1975). A new telescope at Llanherne, which is capable of detecting the RH and LH circular components of incident radiation, is being used in conjunction with these analysers to yield information of the hyperfine polarization structure of Jupiter’s decametric radio emission. This paper is a preliminary report of this investigation.

A radio method of searching for fine structure in H 11 regions

1967 ◽  
Vol 31 ◽  
pp. 237
Author(s):  
O. B. Slee
Keyword(s):  
Fine Structure ◽  
Radio Emission ◽  
Electron Density ◽  
Path Length ◽  
Low Frequency ◽  
Radio Sources ◽  
Average Electron Density ◽  
Scale Size ◽  
Average Electron ◽  
Radio Method

Fine structure with a scale size of about 10-3pc in the galactic ionized hydrogen may scatter the low-frequency radio emission of extragalactic sources with intrinsically small angular diameters, thus making them apparently large. For example, application of the Chandrasekhar scattering formula to a path length of 100 pc through an H 11 region with an average electron density of 0·1 cm-3, and structure of scale size 10-3pc filling 1% of the volume, results in a scattering to half-brightness points of 8″ (arc) at 38 MHz. Radio sources with apparent angular sizes of this amount should be partially resolved by an interferometer with an effective baseline of about 10 000 wavelengths.

scholarly journals The search for radio emission from exoplanets using LOFAR beam-formed observations: Jupiter as an exoplanet

2019 ◽  
Vol 624 ◽  
pp. A40 ◽  
Author(s):  
Jake D. Turner ◽  
Jean-Mathias Grießmeier ◽  
Philippe Zarka ◽  
Iaroslavna Vasylieva
Keyword(s):  
Radio Emission ◽  
Low Frequency ◽  
Scaling Factor ◽  
Theoretical Studies ◽  
Radio Bursts ◽  
Post Processing ◽  
Sensitivity Limit ◽  
Circularly Polarized ◽  
Peak Flux ◽  
Emission Detection

Context. The magnetized solar system planets are strong radio emitters and theoretical studies suggest that the radio emission from nearby exoplanets in close-in orbits could reach intensity levels 103–107 times higher than Jupiter’s decametric emission. Detection of exoplanets in the radio domain would open up a brand new field of research, however, currently there are no confirmed detections at radio frequencies. Aims. We investigate the radio emission from Jupiter, scaled such that it mimics emission coming from an exoplanet, with low-frequency beam-formed observations using LOFAR. The goals are to define a set of observables that can be used as a guideline in the search for exoplanetary radio emission and to measure effectively the sensitivity limit for LOFAR beam-formed observations. Methods. We observe “Jupiter as an exoplanet” by dividing a LOFAR observation of Jupiter by a down-scaling factor and adding this observation to beam-formed data of the “sky background”. Then we run this artificial dataset through our total intensity (Stokes-I) and circular polarization (Stokes-V) processing and post-processing pipelines and determine up to which down-scaling factor Jupiter is still detected in the dataset. Results. We find that exoplanetary radio bursts can be detected at 5 pc if the circularly polarized flux is 105 times stronger than the typical level of Jupiter’s radio bursts during active emission events (~4 × 105 Jy). Equivalently, circularly polarized radio bursts can be detected up to a distance of 20 pc (encompassing the known exoplanets 55 Cnc, Tau Boötis, and Upsilon Andromedae) assuming the level of emission is 105 times stronger than the peak flux of Jupiter’s decametric burst emission (~6 × 106 Jy).

scholarly journals Limits on absorption from a 332-MHz survey for fast radio bursts

2020 ◽  
Vol 493 (3) ◽  
pp. 4418-4427 ◽  
Author(s):  
K M Rajwade ◽  
M B Mickaliger ◽  
B W Stappers ◽  
C G Bassa ◽  
R P Breton ◽  
...  
Keyword(s):  
Radio Emission ◽  
Compton Scattering ◽  
Low Frequency ◽  
Radio Bursts ◽  
Intensity Mapping ◽  
The Past ◽  
Upper Limit ◽  
Shock Region ◽  
Absorption Models ◽  
Post Shock

ABSTRACT Fast radio bursts (FRBs) are bright, extragalactic radio pulses whose origins are still unknown. Until recently, most FRBs have been detected at frequencies greater than 1 GHz with a few exceptions at 800 MHz. The recent discoveries of FRBs at 400 MHz from the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope have opened up possibilities for new insights about the progenitors while many other low-frequency surveys in the past have failed to find any FRBs. Here, we present results from an FRB survey recently conducted at the Jodrell Bank Observatory at 332 MHz with the 76-m Lovell telescope for a total of 58 d. We did not detect any FRBs in the survey and report a 90${{\ \rm per\ cent}}$ upper limit of 5500 FRBs per day per sky for a Euclidean Universe above a fluence threshold of 46 Jy ms. We discuss the possibility of absorption as the main cause of non-detections in low-frequency (<800 MHz) searches and invoke different absorption models to explain the same. We find that Induced Compton Scattering alone cannot account for absorption of radio emission and that our simulations favour a combination of Induced Compton Scattering and Free-Free Absorption to explain the non-detections. For a free–free absorption scenario, our constraints on the electron density are consistent with those expected in the post-shock region of the ionized ejecta in superluminous supernovae.

scholarly journals Pecularities of the Dynamic Spectra of Type V Solar Radio Bursts

1980 ◽  
Vol 86 ◽  
pp. 277-280
Author(s):  
L. M. Bakunin ◽  
A. K. Markeev ◽  
V. V. Fomichev ◽  
I. M. Chertok
Keyword(s):  
Fine Structure ◽  
Radio Emission ◽  
Solar Radio ◽  
Second Harmonic ◽  
Emission Characteristics ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Dynamic Spectra ◽  
Type V

The data on type V solar radio bursts obtained at IZMIRAN with the 45-90 MHz radiospectrograph are analyzed. A great variety and complexity in the dynamic spectra of these events is found. A number of categories of bursts with different emission characteristics of the leading and following edges are distinguished. A number of types of fine structure were found in the dynamic spectra of many bursts. Type V bursts, for which the radio emission at the fundamental and the second harmonic is clearly observed are analyzed.

scholarly journals Fine Structure in Type IV Solar Radio Bursts

1974 ◽  
Vol 57 ◽  
pp. 291-292
Author(s):  
C. Caroubalos ◽  
M. Pick ◽  
C. Chiuderi ◽  
R. Giachetti ◽  
H. Rosenberg ◽  
...  
Keyword(s):  
Fine Structure ◽  
High Frequency ◽  
Solar Radio ◽  
Low Frequency ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Type Iv ◽  
Low Frequency Oscillations ◽  
Solar Type ◽  
Frequency Radiation

(Solar Phys.). The fine structure in solar type IV radio bursts was studied using the 169 MHz Nançay radioheliograph and the 60 channel radiospectrograph at Utrecht (160–320 MHz). The observed fine structure includes pulsating structure, zebra patterns (parallel drifting bands) and intermediate drift bursts. All are considered as modulation of high frequency radiation by low frequency oscillations or as the result of up conversion of low frequency oscillations to higher frequencies (Rosenberg, 1973).

scholarly journals Optical Properties of Polyvinyl Alcohol Films Modified with Silver Nanoparticles

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Vladimir Agabekov ◽  
Nadezhda Ivanova ◽  
Viacheslav Dlugunovich ◽  
Igor Vostchula
Keyword(s):  
Optical Properties ◽  
Polyvinyl Alcohol ◽  
Uv Light ◽  
Incident Radiation ◽  
Light Passing ◽  
Axial Tension ◽  
Linearly Polarized ◽  
Phase Plates ◽  
Elliptically Polarized ◽  
Polyvinyl Alcohol Films

Polyvinyl alcohol (PVA) films modified with Ag nanoparticles and orientated by single-axial tension do not possess dichroism at light passing as well as the film that is cross-linked under the action of bichromates and UV light. These films are double-ray refracting and behave themselves as phase plates that transform linearly polarized incident radiation to elliptically polarized one. The film of latter type has optical properties of reflective diffuse polarizer with polarizing ability ~0.8 in the range of observation angles from 20° to 80°.

A Study on the Fine Structure of the Lateral Line Organ of the Sea Eel

1973 ◽  
Vol 31 ◽  
pp. 648-649
Author(s):  
K. Hama
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Lateral Line ◽  
Low Frequency ◽  
Sensory Cells ◽  
Apical Surface ◽  
Voltage Electron ◽  
Sensory Epithelia ◽  
Low Frequency Vibration ◽  
Transmission Electron

The lateral line organs of the sea eel consist of canal and pit organs which are different in function. The former is a low frequency vibration detector whereas the latter functions as an ion receptor as well as a mechano receptor.The fine structure of the sensory epithelia of both organs were studied by means of ordinary transmission electron microscope, high voltage electron microscope and of surface scanning electron microscope.The sensory cells of the canal organ are polarized in front-caudal direction and those of the pit organ are polarized in dorso-ventral direction. The sensory epithelia of both organs have thinner surface coats compared to the surrounding ordinary epithelial cells, which have very thick fuzzy coatings on the apical surface.

The GLEAM 4-Jy Sample: The brightest radio-sources in the southern sky

2019 ◽  
Vol 15 (S356) ◽  
pp. 375-375
Author(s):  
Sarah White
Keyword(s):  
Radio Emission ◽  
Active Galactic Nuclei ◽  
Visual Inspection ◽  
Low Frequency ◽  
Galactic Nuclei ◽  
Radio Sources ◽  
Relativistic Jets ◽  
The Galaxy ◽  
Murchison Widefield Array ◽  
Past Activity

AbstractLow-frequency radio emission allows powerful active galactic nuclei (AGN) to be selected in a way that is unaffected by dust obscuration and orientation of the jet axis. It also reveals past activity (e.g. radio lobes) that may not be evident at higher frequencies. Currently, there are too few “radio-loud” galaxies for robust studies in terms of redshift-evolution and/or environment. Hence our use of new observations from the Murchison Widefield Array (the SKA-Low precursor), over the southern sky, to construct the GLEAM 4-Jy Sample (1,860 sources at S151MHz > 4 Jy). This sample is dominated by AGN and is 10 times larger than the heavily relied-upon 3CRR sample (173 sources at S178MHz > 10 Jy) of the northern hemisphere. In order to understand how AGN influence their surroundings and the way galaxies evolve, we first need to correctly identify the galaxy hosting the radio emission. This has now been completed for the GLEAM 4-Jy Sample – through repeated visual inspection and extensive checks against the literature – forming a valuable, legacy dataset for investigating relativistic jets and their interplay with the environment.

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