DC Electric Field Acceleration of Ions in Solar Flares

It is shown that the seed particles required for solar flare energetic particles and γ-ray bursts can be generated through the DC electric field acceleration of thermal ions. For an electric field strength on the order of but less than the Dreicer field (the critical field strength above which the entire electron distribution is in the runaway regime), a significant fraction of the thermal ions is accelerated up to a velocity in the range 0.1-1 υ_the where υ_the is the electron thermal velocity (giving ion energies up to 10-1000 keV nucleon^-1). These ions are then available for additional acceleration by waves, or may be further accelerated in the current channels themselves if the electric field exceeds the Dreicer field. Heavier ions are found to have lower thresholds for runaway acceleration than protons and are therefore expected to have enhanced abundances at the energies to which they are accelerated. Under the conditions required for proton acceleration, the entire population of ions more massive than lithium is accelerated up to the electron drift velocity.