Ion bunching as a source of field-aligned currents in space plasmas

摘要

Summary from only given. A spatially inhomogeneous population of heavy minority ions in a magnetized plasma can be produced e.g., by ionization out of an injected neutral cloud, or by the passage of the plasma through a region with rapidly changing transverse electric field. In both cases, the result can be a periodic bunching of the heavy ions, which can persist far from the source of the inhomogeneity. Three separate works on such ion bunching are compared and put into a common frame: (1) ion phase space bunches which were optically observed from ground in the CRRES releases by Bernhardt et al., and interpreted in terms of weak injection, (2) the CRIT I and CRIT II releases which were in the range between weak and strong injection, and where the electric field and the current systems were measured in situ, and (3) the model by Rothweli et al. where oxygen ion bunching magnetotail is proposed to be an important mechanism in the auroral current system.