May 21, 2010, 12:00 pm - 1:00 pm

May 21, 2010, 12:00 pm - 1:00 pm

The role of magnetic reconnection in solar wind-magnetosphere coupling

John C. Dorelli (Geospace Physics Laboratory)

It is widely accepted that magnetic reconnection is responsible for the relationship between geomagnetic activity and the state of the solar wind. Ideally, we would like to capture this relationship with a predictively powerful function which relates solar wind parameters (observable with solar wind monitors at 1 AU) to the state of the magnetosphere (as measured, for example, by the geomagnetic indices). Many such solar wind-magnetosphere coupling functions have appeared in the literature over the years; for various reasons, however, properly incorporating the physics of magnetopause reconnection has been very challenging. Here, we review recent attempts to use global magnetohydrodynamics (MHD) simulations to guide the first principles derivation of solar wind-magnetosphere coupling functions which include such effects as the magnetopause density and magnetic field asymmetries and the inherent three-dimensionality of the subsolar magnetopause stagnation flow. Starting from the MHD equations, we derive a new expression relating the magnetopause reconnection rate to the state of the solar wind plasma. While our new coupling function is consistent with global MHD simulations, it cannot explain several prominent features of the solar-wind-magnetopause interaction. We explore several possible reasons for this discrepancy and suggest that deriving predictively powerful first-principles solar wind-magnetosphere coupling functions will likely involve incorporating several important kinetic effects which are not captured by the MHD equations.

The Radiation Belt Environment Model: The Controversies

Mei-Ching H. Fok (Geospace Physics Laboratory)

A Radiation Belt Environment (RBE) Model has been developed at Goddard to understand Earth's radiation belt dynamics and to provide prediction of the radiation environment. Since its birth in year 2000 to present, the RBE model is constantly questioned by some researchers in the Space Physics community. We will present a brief description of our modeling methodology, the criticisms from the community, and how we clarify the misunderstanding and survive.