Local clouds: Ionization, temperatures, electron densities and interfaces,from GHRS and IMAPS spectra of epsilon Canis Majoris

The composition and physical properties of several local clouds, including the Local Interstellar Cloud (LIC) in which the Sun is embedded, are derive d from absorption features in the UV spectrum of the star epsilon Chla. We derive temperatures and densities for three components by combining our int erpretations of the ionization balance of magnesium and the relative popula tion of CII in an excited fine-structure level. We find that for the LIC n( e) = 0.12 +/- 0.05 cm(-3) and T = 7000 +/- 1200 K. We derive the ionization fractions of hydrogen and discuss the ionizing processes. In particular th e hydrogen and helium ionizations in the LIC are compatible with photoioniz ation by the local EUV radiation fields from the hot stars and the cloud in terface with the hot gas. We confirm the detection of high ionization speci es: Si III is detected in all clouds and C IV in two of them, including the LIC, suggesting the presence of ionized interfaces around the local clouds .