  As gas flowed from the solar accretion disk or solar nebula onto the
proto-Sun, magnetic pressure gradients in the solar magnetosphere and the inner
solar nebula provided an environment where some of this infalling flow was
diverted to produce a low pressure, high temperature, gaseous, "infall"
atmosphere around the inner solar nebula. The pressure in this inner disk
atmosphere was mainly dependant on the accretion flow rate onto the star. High
flow rates implied relatively high pressures, which decreased over time as the
accretion rate decreased.
  In the first hundred thousand years after the formation of the solar nebula,
accretional flow gas pressures were high enough to create submicron-sized
Refractory Metal Nuggets (RMNs) - the precursors to Calcium Aluminum Inclusions
(CAIs). Optimal temperatures and pressures for RMN formation may have occurred
between 20,000 to 100,000 years after the formation of the solar nebula. It is
possible that conditions were conducive to RMN/CAI formation over an eighty
thousand year timescale. The "infall" atmosphere and the condensation of
refractory particles within this atmosphere may be observable around the inner
disks of other protostellar systems.
  The interaction of forces from magnetic fields with the radiation pressure
from the proto-Sun and the inner solar accretion disk potentially produced an
optical-magnetic trap above and below the inner solar nebula, which provided a
relatively stable environment in which the RMNs/proto-CAIs could form and grow.
These RMN formation sites only existed during accretion events from the
proto-solar disk onto the proto-Sun. As such, the formation and growth time of
a particular RMN was dependent on the timescale of its nascent accretion event.
