  Observations reveal that strong solar flares and coronal mass ejections tend
to occur in complex active regions characterized by delta-sunspots, spot
rotation, sheared polarity inversion lines (PILs), and magnetic flux ropes.
Here we report on the first modeling of spontaneous delta-spot generation as a
result of flux emergence from the turbulent convection zone. Utilizing
state-of-the-art radiative magnetohydrodynamics code R2D2, we simulate the
emergence of a force-free flux tube in the convection zone that stretches down
to -140 Mm. Elevated by large-scale convective upflows, the tube appears on the
photosphere as two emerging bipoles. The opposite polarities collide against
each other due to the subsurface connectivity, and they develop into a pair of
closely-packed delta-spots. The Lorentz force drives the spot rotation and a
strong counter-streaming flow of 10 km/s at the PIL in delta-spots, which, in
tandem with local convection, strengthens the horizontal field to 4 kG and
builds up a highly-sheared PIL. In the atmosphere above the PIL, a flux rope
structure is created. All these processes follow the multi-buoyant segment
theory of the delta-spot formation, and they occur as a natural consequence of
interaction between magnetic flux and turbulent convection, suggesting that the
generation of delta-spots and the resultant flare eruptions may be a
stochastically determined process.
