Plasmaspheric Dynamics: Solar-Wind/IMF and Sub-Auroral Coupling 

J. Goldstein, B. Sandel, J. Kozyra, A. Mannucci 


The images produced by the IMAGE extreme ultraviolet (EUV) imager have provided
the first global view of plasmaspheric dynamics, including the process of
erosion and the formation and evolution of drainage plumes. The traditional
picture holds that the zero-order behavior of the plasmasphere is described by
superposition of corotation and solar-wind-driven sunward convection. We test
this long-standing hypothesis by comparing EUV images and the output of a
plasmapause evolution model driven by a time-varying Volland-Stern electric
potential field. Volland-Stern simulations of two June 2001 erosion events
reproduce the EUV plasmapause position on the dawnside, but place it too far
from Earth near dusk, implying strong duskside flows not in the model.
Low-altitude DMSP data show that duskside flows are often enhanced by the
sub-auroral polarization stream (SAPS) phenomenon which couples the ring
current, ionosphere and plasmasphere together. Our simple ad-hoc SAPS model
corrects the duskside plasmapause position in the model. Thus, both convection
and SAPS play a significant role in the global dynamics of the plasmasphere
during geomagnetic disturbances. Analysis of DMSP data and model results
indicate that SAPS flows may be responsible for a duskside "undulation" of the
plasmapause observed on 17 April 2002. There is also evidence that SAPS plays a
significant role in the creation of "tongue"-like regions of enhanced
ionospheric/plasmaspheric total electron content (TEC) observed by the GPS
network to extend poleward from low latitudes.

_______________ 
Presentation, Fall Meeting, American Geophysical Union, San Francisco, USA, 
8-12 December 2003