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Competing atomic processes in Ba and Sr injection critical velocity experiments
Author(s) -
Newell Patrick T.,
Torbert R. B.
Publication year - 1985
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl012i012p00835
Subject(s) - ionization , atomic physics , electron , physics , limiting , population , ion , critical ionization velocity , radiation , plasma , nuclear physics , mechanics , mechanical engineering , demography , quantum mechanics , sociology , engineering
The critical ionization velocity effect requires a superthermal electron population to ionize through collisional impact. Such superthermal electrons can however lose energy to competing atomic processes, as well as to ionization, thus limiting the efficiency of the effect. Considering Ba and Sr magnetospheric injection experiments designed to test the CIV theory, we find that in both cases roughly 60% of the superthermal electron energy is lost on exciting line radiation. Moreover, energy loss to background neutral oxygen places a strict limit on the injected cloud densities for which critical velocity effects are possible; a finding which explains the consistently negative results in radial injection experiments.