NASA/GSFC, Code 682, Greenbelt, MD 20771

Deducing the physical processes responsible for particle acceleration in solar flares will be a primary challenge for the HESSI project. Acceleration by DC electric fields is a process that is likely to be important for the impulsive phase acceleration of electrons and ions. Models based upon this mechanism have distinctive features that can be tested with HESSI and related observations. These models can be classified into three general categories, characterized by the electric field being less than, on the order of, or greater than the classical Dreicer field. I will review these models, with emphasis upon their observational consequences.