On the origin of polar ion streams

It is reaffirmed in this reply that the 'classical' polar wind is based on the thermal escape of the light ions H(+) and He(+). It is asserted that the polar ion flow observations presented in the Gurgiolo and Burch (1985) comment paper, made by the High Altitude Plasma Instrument (HAPI) instrument on Dynamics Explorer-1 (DE), are O(+) and that the probable origin of these ions, which is consistent with the observations, is a highly localized region in the dayside polar cleft; this is a distinctly different source region than that of the polar wind. Velocity and mass selection, as a result of E x B convection acting on ions from a localized source region in the polar cusp or the dayside polar cap boundary, determines the measured HAPI ion distribution. The Retarding Ion Mass Spectrometer instrument on DE, during the same time period, was measuring the light ion polar wind with flow energies of less than 2.5 eV which originated in the polar cap ionosphere very near the north magnetic pole.