Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004aas...20510616s&link_type=abstract
American Astronomical Society Meeting 205, #106.16; Bulletin of the American Astronomical Society, Vol. 36, p.1523
Astronomy and Astrophysics
Astronomy
Scientific paper
Theories of cosmic ray acceleration by supernova remnants predict the existence of regions of intense magnetohydrodynamic turbulence upstream and downstream of the shock wave. Such regions are observed in the case of shock waves in the interplanetary medium, and the interplanetary turbulence possesses substantial density fluctuations. In the interplanetary medium, such turbulent regions produce enhanced radio propagation effects such as scintillations and angular broadening. In this paper, we report a search for enhanced angular broadening of the radio sources J0547+273 and J0128+631, observed through the supernova remnants S147 and G127.1+0.5, respectively. The observations were made with the Very Long Baseline Array of the National Radio Astronomy Observatory in the Fall of 2002. Observations were made at wavelengths of 6, 13, 18, and 21 cm. These multifrequency observations allow the scattered and intrinsic structures of these sources to be distinguished. For both sources, angular broadening attributable to interstellar turbulence was measured. The scattering sizes correspond to 1 GHz angular diameters (FWHM) of 8.9 milliarcseconds (mas) for J0128+631 and 6.4 mas for J0547+273, with uncertainties of about 1 mas for both sources. The expected ``incidental'' angular broadening due to the interstellar medium along these lines of sight was estimated from an updated version of the model of Lazio and Cordes (ApJ 479, 238, 1998). The incidental angular size estimates are 9.5 mas and 6.5-7.0 mas for J0128+631 and J0547+273, respectively. We therefore find no evidence for an enhancement of scattering, and thus intense turbulence, associated with either supernova remnant. Quantitative limits on the properties of waves and turbulence will be presented. This work was supported by grant ATM03-54782 from the Division of Atmospheric Sciences, National Science Foundation.
Spangler Steve
Spitler Lee
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