FAST GALACTIC DYNAMOS AND INTERSTELLAR MAGNETIC-BUBBLES

Large (> 100 pc) interstellar magnetic bubbles are necessary in the co smic-ray-driven fast galactic dynamo, as pioneered by Parker in 1992. In a first part, a look is made at the available data on nearby (< 100 0 pc) large interstellar magnetic bubbles. Here the magnetic field str ength B in a large shell of density n around an OB association is foun d to be a few times greater than that outside in the general interstel lar medium, varying typically like B approximately n, as expected for a shocked medium. In a second part, some tests are made of the predict ions about interstellar magnetic bubbles made by the theory of a cosmi c-ray driven fast galactic dynamo. The bubble tests generally support the idea of a cosmic-ray-driven fast galactic dynamo for the Milky Way .