Other
Scientific paper
Dec 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...437..770m&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 437, no. 2, p. 770-780
Other
63
Coulomb Collisions, Equipartition Theorem, Hot Electrons, Interstellar Matter, Shock Waves, Stellar Luminosity, Supernova Remnants, Thermionic Emission, Boltzmann Transport Equation, Energy Distribution, Ionization, Mathematical Models, Rosat Mission, Thermal Shock
Scientific paper
Nonequipartition between the electron and the ion temperatures, and nonequilibrium ionization are discussed in view of thermal X-ray emission from young supernova remnants (SNRs). For electron heating we consider Coulomb collisions with ions in the postshock region and derive an analytical solution for the electron temperature under the adiabatic condition. By Taylor expansion of the solution, we obtain the electron temperature as a function of the electron density, time, and the shock velocity or the shock temperature (Ts. Defining the equipartition time (Spitzer 1962), tEeq, it is shown that the electron temperature, Te, increases to be approximately equals 0.1 Ts and 0.3 Ts in 10-3 tEeq and 10-2 tEeq, respectively. The result is applied to the self-similar solutions for SNRs in the adiabatic phase, i.e., the free expansion phase and the Sedov phase. We predict a slower variation of the electron temperature than the shock temperature in SNRs expanding into a uniform density medium, while a faster decrease of the electron temperature than the shock temperature in explosions out of the circumstellar matter. We demonstrate the existence of an electron temperature plateau in the shocked matter of an SNR and give analytical expression for the electron temperature and the resultant free-free luminosity. In the free expansion phase, the electron temperatures of the reverse- and the blast-shocked matter are closer to each other than in the case of full equipartition within the shock. This results in a larger difference in the free-free luminosities of the two shocks than the case of full equipartition. Ionization processes are discussed in the framework of the eigenvalue problem to find the key matrix element, which is a pivot of the transformation, and gives the characteristic time constant. The ionization time approximately equals 1012ne-1 s, where ne is the electron density, and has no systematic dependence either on the electron temperature or the atomic number. The ionization state as well as the electron temperature of the shocked matter scales as ne t, and the emission from SNRs can be characterized by a couple of parameters (Te, net). While inner shell ionization followed by fluorescence lines is important in compression waves, radiative recombination followed by cascade lines is important in rarefaction waves.
No associations
LandOfFree
Nonequilibria in thermal emission from supernova remnants does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Nonequilibria in thermal emission from supernova remnants, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nonequilibria in thermal emission from supernova remnants will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1326898