Previous abstract Next abstract
Session 44 - The Local Diffuse ISM.
Display session, Tuesday, June 11
A model for the small scale structure, kinematics and origin of interstellar gas near the Sun is presented. The salient feature of this model is that the LISM properties can be explained if a fragment of an expanding superbubble shell, due to stellar activity in the Scorpius-Ophiuchus Association (SCA), has encompassed the Sun. For instance, the observed small scale structure (\sim1 velocity component per 1.5 pc), kinematics (consistent with superbubble shell models), and magnetic field (consistent with field embedded in superbubble shell) support the view that the Sun is at the edge of, or embedded in, the fragmenting shell. The expansion of the Loop I shock front was halted by collision with the Aquila Rift molecular cloud, as is seen by comparing the low latitude radio continuum extension of the North Polar Spur with CO maps. This collision appears to have ablated material from the molecular cloud, accounting for the larger nearby column densities in the longitude interval 0^o-60^o compared to the opposite direction towards CMa. The fragmenting superbubble shell is a likely site for the location of dense (\sim 10^5 cm^-3 ) small (<100 au) features found to contain up to 15% of diffuse ISM. Thus, an encounter between the Sun and a dense interstellar cloud fragment within the next 10^5 years becomes a possibility. Such an encounter would have a dramatic effect on the galactic environment of the Sun, the physical properties of the heliosphere, the physical properties of the Earth's magnetosphere, mesosphere chemistry, and possibly also the terrestrial climate.
Program listing for Tuesday