  Most Gamma-ray bursts (GRBs) have erratic light curves, which demand that the
GRB central engine launches an episodic outflow. Recent Fermi observations of
some GRBs indicate a lack of the thermal photosphere component as predicted by
the baryonic fireball model, which suggests a magnetic origin of GRBs. In view
that powerful episodic jets have been observed along with continuous jets in
other astrophysical black hole systems, here we propose an intrinsically
episodic, magnetically-dominated jet model for GRB central engine. Accumulation
and eruption of free magnetic energy in the corona of a
differentially-rotating, turbulent accretion flow around a hyperaccreting black
hole lead to ejections of episodic, magnetically dominated plasma blobs. These
blobs are accelerated magnetically, collide with each other at large radii,
trigger rapid magnetic reconnection and turbulence, efficient particle
acceleration and radiation, and power the observed episodic prompt gamma-ray
emission from GRBs.
