The Heliosphere as a Probe of Small Scale Structure

The heliosphere serves as a probe of interstellar material (ISM) close to the Sun. Measurements of ISM inside and outside of the heliosphere show that we reside in typical warm partially ionized ISM that can be successfully modeled using equilibrium photoionization models. The heliosphere wake leaves a similar to 200 x 1000 AU trail in space of low density, n < 0.05 cm(-3), cooling plasma comingled with ISM. The closest ISM flows through the solar vicinity at V-LSR, similar to 20 km s(-1), with an upwind direction towards the Scorpius-Centaurus Association. Clouds in this flow have thicknesses typically < 1 pc. The flow is decelerating, with velocity variations of similar to 3 - 4 km s-1 pc(-1). The alpha Oph sightline shows evidence of a cold, possibly tiny, cloud.