Improvements to the HAF solar wind model for space weather predictions

We have assembled and tested, in real time, a space weather modeling system that starts at the Sun and extends to the Earth through a set of coupled, modular components. We describe recent efforts to improve the Hakamada-Akas ofu-Fry (HAF) solar wind model that is presently used in our geomagnetic st orm prediction system. We also present some results of these improvement ef forts. In a related paper, Akasofu [2001] discusses the results of the firs t 2 decades using this system as a research tool and for space weather pred ictions. One key goal of our efforts is to provide quantitative forecasts o f geoeffective solar wind conditions at the L1 satellite point and at Earth . Notably, we are addressing a key problem for space weather research: the prediction of the north-south component (B-z) of the interplanetary magneti c field. This parameter is important for the transfer of energy from the so lar wind to the terrestrial environment that results in space weather impac ts upon society. We describe internal improvements, the incorporation of ti mely and accurate boundary conditions based upon solar observations, and th e prediction of solar wind speed, density, magnetic field, and dynamic pres sure. HAF model predictions of shock arrival time at the L1 satellite locat ion are compared with the prediction skill of the two operational shock pro pagation models: the interplanetary shock propagation model (ISPM) and the shocktime-of-arrival (STOA) model. We also show model simulations of shock propagation compared with interplanetary scintillation observations. Our mo deling results provide a new appreciation of the importance of accurately c haracterizing event drivers and for the influences of the background helios pheric plasma on propagating interplanetary disturbances.