Ionization Processes in the Local Interstellar Medium: Effects of the Hot Coronal Substrate
Abstract
Detailed photoionization calculations are presented for the local interstellar cloud in which the sun is embedded. The EUV radiation field is considered with contribution from discrete stellar sources and from a thermal bremsstrahlung-radiative recombination spectrum emitted from the surrounding 10 to the 6th K coronal substrate. Lower limits to the fractional ionization of hydrogen and helium are established at 0.17 and 0.30, respectively. The high He ionization fraction results primarily from very strong line emission below 500 A, originating in the surrounding coronal substrate, while the H ionization is dominated by the EUV radiation from the discrete stellar sources. The dual effects of thermal conduction and the EUV spectrum of the 10 to the 6th K plasma on ionization in the cloud skin are explored.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1990
- DOI:
- 10.1086/169440
- Bibcode:
- 1990ApJ...364..573C
- Keywords:
-
- Gas Ionization;
- Interstellar Matter;
- Photoionization;
- Ultraviolet Spectra;
- Abundance;
- Bremsstrahlung;
- Helium;
- Hydrogen;
- Ion Density (Concentration);
- Astrophysics;
- ATOMIC PROCESSES;
- INTERSTELLAR: MATTER;
- ULTRAVIOLET: SPECTRA