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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, A03215, doi:10.1029/2005JA011084, 2006

Magnetospheric convection and thermal ions in the dayside outer magnetosphere

S.-H. Chen

Universities Space Research Association, Columbia, Maryland, USA


T. E. Moore

Heliospheric Physics Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA


Abstract

We have surveyed 3.5 years of Polar Thermal Ion Dynamics Experiment (TIDE) data between 1 January 2000 and 30 June 2003, when Polar apogee paths (sections of orbits with geocentric distances r > 5 R E ) were in the dayside outer magnetosphere, to study the spatial distribution of thermal ions and the magnetospheric convection paths of the thermal ions, as a function of interplanetary magnetic field (IMF) orientation. We have found a dawn-dusk asymmetry in the occurrence of detectable thermal ions above the instrument threshold. The occurrence rate was significantly higher at the duskside. The probability of observing thermal ions, particularly at 1300–1600 local time (LT) near the magnetopause, was >50%, compared with <30% at the dawnside. We interpret the thermal ion events as the result of plasmaspheric drainage plumes, as observed by IMAGE spacecraft or geosynchronous orbiters. The episodic appearance of the thermal ions in the outer magnetosphere could be a significant factor for the dynamo process of global magnetospheric convection. The variation of the convection pattern due to the IMF orientation is consistent with equatorward and poleward reconnection scenarios that superimpose dayside convection driven by reconnection on top of the background convection driven by a viscous interaction at the magnetopause, together with the corotation of the magnetospheric plasma with the ionosphere.

Received 16 February 2005; accepted 4 January 2006; published 18 March 2006.

Keywords: magnetospheric convection; reconnection; thermal ions.

Index Terms: 2740 Magnetospheric Physics: Magnetospheric configuration and dynamics; 2784 Magnetospheric Physics: Solar wind/magnetosphere interactions; 2736 Magnetospheric Physics: Magnetosphere/ionosphere interactions (2431); 2760 Magnetospheric Physics: Plasma convection (2463); 2723 Magnetospheric Physics: Magnetic reconnection (7526, 7835).

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Citation: Chen, S.-H., and T. E. Moore (2006), Magnetospheric convection and thermal ions in the dayside outer magnetosphere, J. Geophys. Res., 111, A03215, doi:10.1029/2005JA011084.