We. Amatucci et al., OBSERVATION OF ION-CYCLOTRON TURBULENCE AT SMALL VALUES OF MAGNETIC-FIELD-ALIGNED CURRENT, Geophysical research letters, 21(15), 1994, pp. 1595-1598
Fluctuations in plasma density are observed in the ion-cyclotron frequ
ency range in a Q-machine plasma column at values of magnetic-field-al
igned current significantly below the critical value for current-drive
n electrostatic ion-cyclotron (CDEIC) waves. These fluctuations arise
from the inhomogeneous energy-density driven (IEDD) instability, are r
elatively broadband, and can have large amplitude compared to CDEIC fl
uctuations. These results impact the interpretation of ion heating and
acceleration in the ionosphere, especially at low-altitude where magn
etic-field-aligned current densities estimated to be large enough to b
e supercritical to current-driven or beam-driven electrostatic ion-cyc
lotron waves are rarely detected.