The physics of the formation and termination of high ion temperature mode (high mode) is studied by controlling density profiles and radial electric field. High ion temperature mode is observed for neutral beam heated plasmas in heliotron/torsatron plasmas (Heliotron-E). This high mode plasma is characterized by a peaked ion temperature profile and is associated with a peaked electron density profile produced by neutral beam fuelling with low wall recycling. This high mode is terminated by flattening of the electron density caused either by gas puffing or by second-harmonic ECH (core density `pump out').