MAGNETIC FIELD STRUCTURE AND COLLECTIVE EFFECTS IN SUPERNOVA REMNANTS

Abstract

ABSTRACT New observations of the northeast rim of the intermediate age supernova remnant IC 443 obtained at 20.9 cm with the VLA have resolved the bright filamentary clouds. The cloud width is consistent with the recombination/cooling length of optical filaments, but inconsistent with the evaporation time predicted for isolated, cold filamentary clouds in a hot interstellar medium. By considering collective evaporative effects among filamentary clouds using an analogous electrostatic model, the rate of evaporation is shown to be decreased by more than a factor of five, resulting in an evaporation length consistent with the observations. In order to investigate magnetic field structure in the regions near supernova remnant filaments, a method quantifying the degree of organization of the local magnetic field in a region is presented. This method takes into account the degree to which the magnetic field direction is preferentially aligned, the degree of linear polarization, and the total intensity. The method is applied to new data from high resolution polarimetric observations of the filamentary structure in the northeast rim of IC 443 obtained at 6.1 cm with the VLA. The local magnetic field is found to be organized in regions preferentially located within the rim of the supernova remnant, and is correlated with regions of relatively high polarized intensity. The size scale of the largest region of field organization associated with IC 443 is approximately 85 arcsec (0.6 pc), and the apparent size scale of local field organization of the ambient interstellar is approximately 35 arcsec (0.25 pc). The direction of the mean field in regions of high local field organization of IC 443 is generally oriented neither parallel nor perpendicular to the rim, suggesting that transverse expansion and cloud crushing have increased the tangential feild component. Significant poliarized brightness extends over 0.5 pc beyond the rim of IC 443 defined by the total intensity and probably represents the outer shock of the supernova blast. The method is next applied to VLA data from the young remnant of Tycho's supernova of 1572 (3C 10), where it is also found that the local magnetic field is organized into regions correlated with regions of relatively high polarized intensity. The size scale of the largest organized region associated with 3C 10 is approximately 110 arcsec (1.33 pc), and the apparent size scale of the local field organization of the ambient interstellar is approximately 30 arcsec (0.36 pc). The direction of the mean field in regions of high local field organization within rim of 3C 10 is generally radial, indicating that cloud crushing and transverse expansion have had minimal effect.