2001/08/17 by J. M. Laming, J. Martin Laming · 6 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Solar and Space Plasma Dynamics #astro-ph
paper · pdf · doi:10.1086/323953
29 pages + 8 figures, accepted for publication by ApJ
arxiv created 2001/08/17 · openalex publication_date 2001/12/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
We consider in more detail a model previously proposed for the hard X-ray (>10 keV) emission observed from the supernova remnant Cas A, whereby electrons are accelerated by lower hybrid waves and radiate bremsstrahlung. We consider both cold and thermal plasma limits of the modified two-stream instability that generates the lower hybrid waves and, by studying the time-dependent ionization balance for various components of the Cas A ejecta and shocked circumstellar medium, find locations within the shell where one or other of the instabilities may occur. Either instability can be effective, with the cold plasma instability imposing fewer constraints on the shocked reflected ion population responsible for exciting the waves. The instability must be located in the ejecta shocked at the earliest times and therefore closest to the contact discontinuity where magnetic fields are expected to be the strongest. The energy deposited in this ejecta by collisions between accelerated and ambient electrons is broadly consistent with that required to reheat this ejecta to the observed temperature of ~ 4 × 10 7 K.