The Great Power-Law in the Sky; the Turbulent Cascade from
Hundreds of Parsecs to Thousands of Kilometers
Ethan Vishniac, Johns Hopkins University
Observations of the ISM seem to show a strong turbulent cascade
extending from scales of tens of parsecs down to 10^8 cm. This
turbulent power spectrum is very roughly consistent with what one
would expect for incompressible hydrodynamic turbulence, in
spite of the fact that the ISM is compressible and magnetized.
Even odder, we see no clear sign that neutral damping has a
dramatic effect on the cascade, in spite of its expected role as a
major sink of kinetic energy. I will discuss an approximate theory
of turbulence in a partially ionized medium which explains these
results, and the current state of numerical simulations designed to
test these ideas.