Parker's Instability, first described in 1966, is thought to put limits on the fraction of pressure support that can come from magnetic fields and cosmic rays in galactic and other astrophysical disks. It has also been implicated as a key process in the formation of interstellar clouds and in the origin and maintenance of the interstellar magnetic field by a galactic dynamo. Our understanding of Parker's Instability and its relevance has changed as often as our understanding of interstellar gas :i.e. a lot. I will discuss old and new work on Parker's Instability and how it ties together our view of the interstellar medium in the disk and halo of our galaxy.
Followed by wine and cheese in Pupin 1402.