2015/04/06 by John C. Raymond, J. C. Raymond, Richard J. Edgar +5 · 1 citation
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Electron #Electron temperature #Ion #Ionosphere and magnetosphere dynamics #Kinetic energy #Line (geometry) #Mean kinetic temperature #Proton #Shock wave #Solar and Space Plasma Dynamics #astro-ph.GA #astro-ph.HE
paper · pdf · doi:10.1088/0004-637x/805/2/152
22 pages, 4 figures ApJ, in press
arxiv created 2015/04/06 · openalex publication_date 2015/05/28 · arxiv updated 2015/06/03 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
ABSTRACT Observations of SN 1006 have shown that ions and electrons in the plasma behind fast supernova remnant shock waves are far from equilibrium, with the electron temperature much lower than the proton temperature and ion temperatures approximately proportional to ion mass. In the ∼360 km s −1 shock waves of the Cygnus Loop, on the other hand, electron and ion temperatures are roughly equal, and there is evidence that the oxygen kinetic temperature is not far from the proton temperature. In this paper, we report observations of the He ii λ 1640 line and the C iv λ 1550 doublet in a 360 km s −1 shock in the Cygnus Loop. While the best-fit kinetic temperatures are somewhat higher than the proton temperature, the temperatures of He and C are consistent with the proton temperature and the upper limits are 0.5 and 0.3 times the mass-proportional temperatures, implying efficient thermal equilibration in this collisionless shock. The equilibration of helium and hydrogen affects the conversion between proton temperatures determined from H α line profiles and shock speeds, and the efficient equilibration found here reduces the shock speed estimates and the distance estimate to the Cygnus Loop of Medina et al. to about 800 pc.