Prior to my position at U Maryland in 2000, I was the Chief Scientist of the Heliophysics Division of NASA/GSFC for 13 years and Senior Scientist, Space Weather for NASA. Prior to joining NASA/GSFC, I was Head of the Solar-Terrestrial Theory Section at the Naval Research laboratory. My research is distinguished by the development of theoretical models to explain major observational problems, and relies heavily on MHD theory and numerical simulation. I was one of the pioneers of large-scale numerical simulations of solar activity. I have made many advances to our understanding of the Sun and Heliosphere including: my foundational work on chromospheric evaporation and the dynamics of coronal loops; my cool loop model for the transition region that links the upper and lower levels of the solar atmosphere; my thermal nonequilibrium model for the formation of coronal condensations, such as filaments/prominences; my breakout model for coronal mass ejections and eruptive flares, which also applies to coronal jets; my Web model for the sources of the slow solar wind; and my theory of helicity condensation that explains many of the long-standing observational puzzles of the Sun's magnetic field. I have also worked extensively on the fundamental theory of magnetic reconnection. My science contributions have been recognized with a number of major awards including: the Fleming Medal from the AGU, the Hale Prize from the AAS, the Lindsay Award from NASA/GSFC, the Hulburt Award from NRL, and elected Fellow of the AGU, APS, and AAS, and Honorary Fellow of the Royal Astronomical Society.