  We reinvestigate the generation and accumulation of magnetic flux in
optically thin accretion flows around active gravitating objects. The source of
the magnetic field is the azimuthal electric current associated with the
Poynting-Robertson drag on the electrons of the accreting plasma. This current
generates magnetic field loops which open up because of the differential
rotation of the flow. We show through simple numerical simulations that what
regulates the generation and accumulation of magnetic flux near the center is
the value of the plasma conductivity. Although the conductivity is usually
considered to be effectively infinite for the fully ionized plasmas expected
near the inner edge of accretion disks, the turbulence of those plasmas may
actually render them much less conducting due to the presence of anomalous
resistivity. We have discovered that if the resistivity is sufficiently high
throughout the turbulent disk while it is suppressed interior to its inner
edge, an interesting steady-state process is established: accretion carries and
accumulates magnetic flux of one polarity inside the inner edge of the disk,
whereas magnetic diffusion releases magnetic flux of the opposite polarity to
large distances. In this scenario, magnetic flux of one polarity grows and
accumulates at a steady rate in the region inside the inner edge and up to the
point of equipartition when it becomes dynamically important. We argue that
this inward growth and outward expulsion of oppositely-directed magnetic fields
that we propose may account for the ~30 min cyclic variability observed in the
galactic microquasar GRS1915+105.
