Dynamics of Ionospheric Ions in the Mid-tail During Disturbed Times
Abstract
Cluster ion measurements made during storms and substorms inside the tail lobes and inside the plasma sheet clearly indicate the ionosphere is supplying a large amount of ionospheric H^+, O^+ (He^+, O++) ions to the magnetospheric tail. We analyze in details the dynamics of these ions and show: -i) that inside the plasma sheet a single injection from the auroral zone is able to enhance the mid-tail content of oxygen ions by 80%. -ii) that inside the lobes, during disturbed times, beams of oxygen ions coming from the dayside are quasi systematically detected with tailward velocities of the order of 30--80 km/s. As a general result, these oxygen ions, still flowing tailward, are more energetic inside the plasma sheet boundary layer that inside the lobe. Using the four Cluster spacecraft we show how these ions are accelerated and heated inside the PSBL. -iii) that plasma sheet disturbances are at the root of Earthward propagating shear Alfvèn waves measured inside the lobe. The wave electric field modulates the energy of the O^+ beams and can give enough drift energy to the cold ionospheric lobe protons to overcome the satellite potential and be detected by the CIS experiment.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....7012S