Cluster ion measurements
Abstract
The Cluster ion spectrometers (CIS) already provided a large amount of new data on the polar cusp, boundary layers composition and dynamics, Plasma Transfer Events (PTE) and Flux Transfer Events (FTE) on the dayside magnetosphere. Plasma ionospheric outflows are currently studied from the mid latitude passes of the Cluster spacecraft over the polar regions. In the plasma sheet, CIS furnished the first direct experimental evidence for the plasma sheet filling with heated ions ejected during the substorm expansion phase and dispersed by time of flight effects. All these results will be briefly reviewed (see Bosqued et al., 2001; Moebius et al., 2001; Sauvaud et al., 2001). This paper will present in details the first observations with Cluster of a dense population of thermal ionospheric ions (H+ , He+ , O+ ) locally "accelerated" perpendicularly to the local magnetic field in a region adjacent to the magnetopause and on its magnetospheric side. Recurrent motions of the magnetopause are, in the presented cases, unexpectedly associated with the appearance, inside closed field lines, of recurrent energy structures of ionospheric ions with energies in the 5 eV to ∼1000 eV range. The heaviest ions being detected with the highest energies. Here the ion behavior results from local electric field enhancements/decreases which adiabatically enhance/lower the bulk energy of a local dense thermal ion population being already there. These results show that the dayside magnetosphere can be mainly populated by plasma of terrestrial origin up to the magnetopause. We will also present results indicating that such a cold and fast drifting ionospheric population is also observed in the plasma sheet. As for the dayside
- Publication:
-
Space Plasma Simulation
- Pub Date:
- 2001
- Bibcode:
- 2001sps..proc..188S