Results 1 - 10 of 2074
Results 1 - 10 of 2074. Search took: 0.027 seconds
|Sort by: date | relevance|
[en] Synthesis radio observations have been made of 27 sources to determine the component polarization at a wavelength of 49 cm. The sources were chosen from a complete flux density limited sample on the basis of relatively little depolarization at shorter wavelengths. The results are presented in the form of integrated component parameters and maps of the total and polarized intensity distributions. The component polarization data have been used to determine, or set limits to, the rate of depolarization, and derived quantities are presented in tabular from for all 94 sources from the complete sample. The results are briefly discussed, and in particular it is noted that bridge emission in double radio sources exhibits a low degree of polarization at 49 cm. It is suggested that this may be the result of depolarization in ionized gas associated with the parent optical object. The observations are consistent with an excess density of order 100 m-3 throughout the bridge region
[en] The strength and direction of the large-scale galactic magnetic field is determined by a regression method. The data on the rotation measures, angular coordinates and redshifts of extragalactic sources from the catalogues of Morris and Tabara, Mitton, Vallee and Kronberg are used. It is shown that the largescale magnetic field lines lie in the galactic plane (b approximately equal to 0 deg) and are directed approximately along the local spiral arm (l=91+-22 deg). The best estimation of the amplitude of the galactic rotation measure is K=25+-10 rad/m2
[en] The Faraday rotation and amplitude data for the period September 1978 through August 1979, recorded from the geostationary satellite SMS (900W) at Natal (5.90S, 35.20W), have been utilized to study the behavior of total electron content (TEC). Apart from diurnal and seasonal behavior of TEC, two characteristic features of the nighttime ionosphere are discussed: (1) a postsunset enhancement in TEC which lasts for several hours following the rapid sunset decrease and (2) the sharp, isolated changes in TEC. In particular, relating to phenomena 2, the depletions in TEC are usually accompanied by a simulataneous increase in fading rate, scintillation index, and amplitude The statistics of their occurrence and nature are described. The average behavior of the signal amplitude after propagating through either a depleted or an enhanced ionosphere is modeled theoretically and shown to be in agreement with the observed experiment behavior
[en] We confirm the reality of a reversal of the sign of the Faraday rotation measure in the Galactic plane in Cygnus (Lazio et al. 1990), possibly associated with the Cygnus OB1 association. The rotation measure changes by several hundred rad m-2 over an angular scale of 2 deg. - 5 deg. We show that a simple model of an expanding plasma shell with an enhanced density and magnetic field can account for the magnitude and angular scale of this feature. This model is consistent with observations of Hα emission as well as other observations in this part of sky. We suggest that this structure is physically associated with a superbubble produced by the Cygnus OB1 association.