Necessary Conditions for E|| in Space

• Inhomogeneous strong B-field such that grad-B drifts dominate over ExB

  • Dipole field! Ubiquitous

• Source of hot plasma

  • Injected directly (accretion disks)
  • Convected from elsewhere (plasmasheet)

• Spinning central magnet?

• Result:

  • Rim feed, axial exit accelerator. Efficient
  • Hot, non-thermal Xray source.