2.4. Magnetic fields and Supernovae (B ~ n1)
There is some nonthermal polarized emission from supernovae, due to synchrotron radiation from relativistic electrons moving in the magnetic fields (located in supernovae shells). Thin shells have been studied at centimetric wavelengths; but thick shells require shorter wavelengths (e.g., Weiler and Sramek 1988; Mineshige et al. 1993).
Theoretically, hot gas escaping from older superbubbles around supernovae and breaking into the galactic halo are said to form a 'galactic fountain' or 'chimney' (e.g., fig. 10 in Kahn & Brett 1993), complete with magnetic reconnections along adjacent galactic fountains. In the shell of a galactic fountain, the magnetic field strength is predicted to be proportional to the shell gas density, i.e., B ~ n1.0, preventing the thickness of the shell to become too small as the shell cools with time.