Jeffrey Linsky
University of Colorado


Structure, kinematics, and quasar scintillation in the nearby ISM


Using high-resolution UV spectra obtained with the GHRS and STIS
instruments on HST and ground-based spectra of the Ca II lines, we
identify 15 coherently moving structures (clouds) of warm
partially-ionized gas in the nearby ISM.

All of these clouds lie within the Local Bubble and within 15 pc of the Sun.

Several are very much closer. These clouds have different velocity
vectors and at least one appears to be a shock front where two clouds
are colliding.

Large amplitude intraday variability of quasars at radio wavelengths
can be explained as scintillation produced by turbulent ionized gas in
the nearby ISM.

For three quasars that have been well monitored at radio wavelengths,
we show that the scintillating screens have transverse velocities
consistent with nearby clouds. The turbulence appears at the edges of
clouds where collisions with adjacent clouds likely occur and where
interstellar UV radiation produces enhanced ionization.