Quantification of tailward cold O(+) beams in the lobe/mantle regions with Geotail data - Constraints on polar O(+) outflows

Over a wide range of the tailward distances in the lobe/mantle regions, the Geotail spacecraft sometimes observed cold O(+) beams (COBs) streaming tailward at a velocity nearly equal to that of the major proton component. The discovery of the ionospheric ions in the distant lobe/mantle leads us to a reexamination of the conventional view which expects these O(+) ions to descend into the plasma sheet because of the ExB drift. In order to clarify the quantitative property of the COBs, we have projected COB parameters onto the polar ionosphere with a simple model that takes into account the velocity filter effect alone. The statistical data set from October 1993 to March 1995 in a solar-minimum period is used in the calculation. The calculated average COB flux in the lobe/mantle corresponds to at least approximately 10 exp 8/sq cm/s O(+) flux at the 1000-km altitude. From the comparison with polar outflows, it is suggested that the O(+) ions originating at the cusp/cleft sometimes need significant additional energization so as to supply the COBs in the distant tail. (Author)