The Accretion Disc Dynamo in the Solar Nebula
  The nearest accretion disc to us in space if not time was the protosolar
nebula. Remnants of this nebula thus potentially offer unique insight into how
discs work. In particular the existence of chondrules, which must have formed
in the disc as small molten droplets, requires strong and intermittent heating
of disc material. We argue that this places important constraints on the way
gravitational energy is released in accretion discs, which are not met by
current shearing--box simulations of MRI--driven dynamos. A deeper
understanding of accretion energy release in discs may require a better model
for these dynamos.
