Dr. Spiro Antiochos of the Naval Research Laboratory's Space Science Division has received the Laboratory's annual E.O. Hulburt Award, NRL's highest civilian honor for scientific achievement. The award, presented to Dr. Antiochos in a ceremony held on September 25, 2006, was established in 1955 to mark the retirement of NRL's first director of research, Dr. E.O. Hulburt.
Head of the Solar Theory Section in the Solar-Terrestrial Relationships Branch, Dr. Antiochos is cited for "outstanding creativity and physical insight in developing theories of solar activity, in particular the breakout model for coronal mass ejections and the thermal nonequilibrium model for prominence formation, and for his scientific leadership and selfless community service, both at the Laboratory and within the international solar physics community."
Dr. Antiochos has pioneered many advances in the rapidly growing field of computational solar physics, most notably, his work on the structure and dynamics of the corona and transition region, coronal condensation, coronal magnetic fields, and magnetic loop theory.
In a seminal contribution, Dr. Antiochos developed the "breakout" model for the initiation of coronal mass ejections (CMEs). It is now recognized that CMEs are the main driver of space disturbances at Earth and are, therefore, the subject of intense investigation by both the solar and space/geophysics communities. The main obstacle in understanding CMEs is the large energy-release rate required to accelerate the erupting plasma and open the coronal magnetic field out to the heliosphere. While this problem has been actively studied by many groups throughout the world, Dr. Antiochos' key insight was that magnetic reconnection between neighboring flux systems allows stressed low-lying magnetic field to expand outward explosively while overlying, unstressed field remains closed. The breakout model has enormous implications for predicting space weather, a major national and international thrust. The model is a direct result of Dr. Antiochos' fundamental work on magnetized plasmas and, especially, magnetic reconnection, work that is now finding application in laboratory plasmas, as well.
Dr. Antiochos is a cofounder of coronal loop theory. Coronal loops are arches of magnetically-confined hot plasma that are the basic building blocks of the corona and transition region. He developed the first numerical model of a coronal loop, and performed the original analytic and numerical modeling of chromospheric evaporation, which showed how coronal loops obtain their mass. It is the basis for all dynamic loop models. He has also made fundamental contributions to the theory of dynamic transition regions in loops, both for quiet Sun and for flares. His model of cool loops to explain the structure of the lower transition region, has inspired a great deal of observational research.
A long-standing solar physics puzzle is the frequent appearance of cool plasma in the midst of the hot corona. Quiescent prominences and filaments are the most common manifestations of this phenomenon, but observations have shown that it occurs in a variety of forms and on a variety of time scales. Dr. Antiochos' work has led the field on this problem and has generated a host of new observational and theoretical research. His thermal nonequilibrium model provides a simple and convincing explanation for both the formation and the recently-discovered dynamics of prominence condensations. These results are the culmination of a long history of work on thermal instability and on active prominences, which have advanced the understanding of coronal condensations and prominence formation to a new level.
The structure of the magnetic field that supports prominence material against gravity has been a question that solar physicists have wrestled with for decades. This issue is at the heart of understanding solar activity, because filament channel magnetic fields are widely believed to provide the free energy that powers flares and coronal mass ejections (CMEs). In a seminal paper, Dr. Antiochos showed how magnetic shear in a three-dimensional (3D) bipolar geometry can account for the mass support and many other observed features of prominences. This forms the basis for much of the present research on prominence structure and eruption.
Most recently, Dr. Antiochos has demonstrated how coronal holes evolve in response to motions of magnetic flux at the solar surface. Coronal holes, where high-speed streams of solar wind originate, are regions of magnetic field that open to the heliosphere rather than looping back down to the solar surfaces, as in active regions and the quiet Sun. Dr. Antiochos has shown that the magnetic fields experience complex 3D reconnection as magnetic bipoles move slowly across the solar surface and interact with the larger global field of the Sun. This new understanding of the 3D aspects of reconnection may revolutionize our understanding of many other solar phenomena that have previously been treated in a two-dimensional fashion.
Dr. Antiochos received his B.S. degree in 1970 from McGill University in Montreal, Canada, and his Ph.D. in 1976 from Stanford University. Prior to joining NRL in 1985, he served as a postdoctoral fellow at the National Center for Atmospheric Research from 1976 to 1978, and as a research associate at Stanford University from 1979 to1984.
In 2005, Dr. Antiochos received the Hale Prize from the Solar Physics Division of the American Astonomical Society (AAS), the highest honor that can be bestowed on a solar physicist. He is a Fellow of the American Geophysical Union, a member of the American Physical Society, the International Astronomical Union, and the AAS. From 1991 to 1993, he served as chair of the AAS Solar Physics Division. Dr. Antiochos, also an adjunct professor in the Department of Atmospheric, Oceanic, and Space Sciences at the University of Michigan, has served as a member of numerous NASA, National Science Foundation and National Academy committees, including chair of the NASA Solar Physics Management Operations Working Group and chair of the Solar-B Science Definition Team. He has authored or coauthored over 100 refereed papers in archival journals, and has also served as co-editor of the AGU Monograph Sun-Earth Plasma Connections and as associate editor of the Journal of Geophysical Research-Space Physics from 1998 to 2001.
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