Abstract. In February 1996, the POLAR spacecraft was placed in an elliptical orbit with a 9 RE geocentric distance apogee in the northern hemisphere and 1.8 RE perigee in the southern hemisphere. The Thermal Ion Dynamics Experiment (TIDE) on POLAR has allowed sampling of the three-dimensional ion distribution functions with excellent energy, angular, and mass resolution. The Plasma Source Instrument (PSI), when operated, allows sufficient diminution of the electric potential to observe the polar wind at very high altitudes. In this paper, we describe the results of a survey of the polar wind characteristics for H + , He + , and O + as observed by TIDE at -5000 km and -8 RE altitudes over the polar cap during April-

Abstract. We report observations of a direct ionospheric plasma outflow response to the incidence of an interplanetary shock and associated coronal mass ejection (CME) upon

Ionospheric ion upwelling in the vicinity of the dayside cleft has been studied, based primarily on data from the Dynamics Explorer 1 spacecraft. Using retarding ion mass spectrometer low‐energy ion data and plasma wave instrument dc electric field data, bulk ion plasma parameters, including ion species density and field‐aligned bulk velocity and flux, have been derived at points within a number of observed upwelling ion events for the ion species H+, He+, O+, and O++. The ion species bulk parameters near the source latitude are examined and compared. We find that the upwelling plasma is rich in O+, which typically comprises ∼90% of the particle density, followed by H+ at somewhat less than 10%, and then He+ and O++, each comprising ∼1% of the upwelling ion particle density. The upwelling O+ ion flux is also commonly dominant over that associated with the other species, with normalized values near the source region which are typically near 109 cm−2 s−1. The fractional upward H+ flux is not as small as the fractional H+ density due to the much larger H+ upward flow velocities. Integration of the product of the normalized upward ion species flux and the upwelling ion occurrence probability (Lockwood et al., 1985) over the source area yields an estimate of the source strength of this low‐altitude cleft region magnetospheric plasma source of 2.6×1025 ions s−1.

Plasma outflows, escaping from Earth through the high-altitude polar caps into the tail of the magnetosphere, have been observed with a xenon plasma source instrument to reduce the floating potential of the POLAR spacecraft. The largest component of H + flow, along the local magnetic field (30 to 60 kilometers per second), is faster than predicted by theory. The flows contain more O + than predicted by theories of thermal polar wind but also have elevated ion temperatures. These plasma outflows contribute to the plasmas energized in the elongated nightside tail of the magnetosphere, creating auroras, substorms, and storms. They also constitute an appreciable loss of terrestrial water dissociation products into space.

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