Rough Equipartition Research Articles

VLBI observations of compact radio sources at 609 megahertz

view Abstract Citations (72) References (43) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS VLBI observations of compact radio sources at 609 megahertz. Wilkinson, P. N. ; Readhead, A. C. S. ; Anderson, B. ; Purcell, G. H. Abstract This paper reports VLBI observations of seven powerful radio sources, obtained using a four-telescope network which, at 609 MHz, gives a maximum resolution of about 5 milliarcsec. Measurements of the closure phase as well as the fringe amplitude have made it possible to make hybrid maps of five of the sources. In many of the sources the similarity between the position angle of the compact structure and that on a much larger scale (at least about 0.5 arcsec) indicates that there is a close relationship between them. This is particularly evident in 3C 84 and 3C 273, where the compact emission region is asymmetrical and has extensions toward structure on the 10-arcsec scale. The data are, in general, explicable in terms of incoherent electron synchrotron radiation with rough energy equipartition between the relativistic particles and the magnetic field; but in CTA 102 and 3C 454.3 the energetics are probably particle dominated. At the epoch of these observations (March 1975) none of the sources had a peak brightness temperature in excess of 1 million K. The lack of frequency dependence in the structure of individual source components implies that they are relatively homogeneous, although more detailed observations at other frequencies are needed to confirm this. Publication: The Astrophysical Journal Pub Date: September 1979 DOI: 10.1086/157296 Bibcode: 1979ApJ...232..365W Keywords: Extragalactic Radio Sources; Quasars; Radio Astronomy; Very Long Base Interferometry; Amplitudes; Astronomical Maps; Synchrotron Radiation; Telescopes; Astrophysics; Radio Maps:Radio Sources; Radio Sources:Compact; Radio Sources:VLB Interferometry full text sources ADS | data products NED (1)

Studies of the vertical structure of horizontal currents near Bermuda

A number of vertical profiles of horizontal motion at a site 70 km south of Bermuda were obtained in 1969 and 1970. An extensive analysis of the distribution of kinetic energy as a function of vertical mode was conducted. Rough equipartition of the kinetic energy into the barotropic (25 ergs/cm3) and lowest baroclinic (20 ergs/cm3) was found. This study was partly prompted by our concern as to whether conventional current measuring techniques, such as current meters and Swallow floats, can adequately resolve the low-frequency evolution of the vertical structure. There seems little doubt that the gross features of the two lowest modes can be monitored by sparse sampling in the vertical, but accurate estimates of their amplitudes may be difficult to obtain owing to aliasing by weak higher-order internal modes.