The presence of H+3 in the interstellar medium was forecast almost four decades ago. Almost three decades ago it was asserted that its reactions with neutral molecular and atomic species directly lead to the production of many of the interstellar molecules that have been discovered by radio and infrared astronomers. With the recent detection of H+3 in interstellar space, astronomers finally hav...

Gas-phase chemistry in the interstellar medium is driven by fast ion-molecule reactions. This, of course, demands a mechanism for ionization, and cosmic rays are the ideal candidate as they can operate throughout the majority of both diffuse and dense interstellar clouds. Aside from driving interstellar chemistry via ionization, cosmic rays also interact with the interstellar medium in ways tha...

A fraction of the interstellar atoms crosses the interface between the solar wind and the ionized component of the local interstellar medium (the heliospheric interface), and enters the heliosphere. The number of penetrating atoms depends on the strength of the atom-plasma interaction, i.e. on the atom type. In this paper we consider the penetration of the interstellar oxygen atoms, and we stud...

I review those properties of the interstellar medium within 15 light-years of the Sun, which will be relevant for the planning of future rapid (vZ0.1c) interstellar space missions to the nearest stars. As the detailed properties of the local interstellar medium (LISM) may only become apparent after interstellar probes have been able to make in situ measurements, the first such probes will have ...

Measurements by dust detectors on interplanetary spacecraft appear to indicate a substantial flux of interstellar particles with masses > 10−12 g. The reported abundance of these massive grains cannot be typical of interstellar gas: it is incompatible with both interstellar elemental abundances and the observed extinction properties of the interstellar dust population. We discuss the likelihood...

NASA’s Interstellar Probe Mission will be the first spacecraft specifically designed to explore the outer solar system, pass through the boundaries of the heliosphere, and sample the nearby interstellar medium. During the spring of 1999, NASA’s Interstellar Probe Science and Technology Definition Team* developed a concept for a mission that will travel to 200400 AU using solar-sail propulsion. ...

We present the results of an Australia Telescope Compact Array (ATCA) survey for intra-day variability (IDV) of the total and polarized flux densities of 118 compact, flat spectrum, extragalactic radio sources from the Parkes 2.7 GHz Survey. A total of 22 total flux density IDV sources were discovered and 15 sources were found to show IDV of their polarized flux density. We discuss the statisti...