Dr. Antiochos Receives AAS Hale Prize; Elected AGU Fellow

3/10/2005 - 9-05r
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Dr. Spiro Antiochos of the Naval Research Laboratory's Space Science Division was twice honored in January with distinguished recognitions. First, he was selected as the recipient of the prestigious Hale Prize from the American Astronomical Society (AAS). Shortly thereafter, Dr. Antiochos was notified of his election to Fellow of the American Geophysical Union (AGU).

The Hale Prize is an international award given by the Solar Physics Division of the AAS and is considered the highest honor that can be bestowed on a solar physicist. Named in memory of astronomer George Ellery Hale, the prize is given nominally every two years for outstanding contributions over an extended period of time. This year's Hale Prize acknowledges Dr. Antiochos for his work on "the thermodynamics and stability of coronal magnetic fields and for his outstanding public service to the community."

AGU Fellowship recognizes Dr. Antiochos 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 leadership in integrating the U.S. solar physics community with the American Geophysical Union." Only 0.1% of the AGU membership is so honored in any given year.

Dr. Antiochos is the head of the Solar Theory Section of the Solar Terrestrial Relationships Branch. His fields of expertise include theoretical solar physics, plasma physics, and computational physics. He is an internationally recognized leader in solar physics whose research is distinguished by the development of innovative models to explain major observational problems. His work relies heavily on magnetohydrodynamic theory and state-of-the-art numerical simulation. Dr. Antiochos is considered a pioneer in the field of computational solar physics.

Dr. Antiochos has made many fundamental advances to our understanding of the Sun. Among his most notable contributions are his work on the structure and dynamics of the corona and transition region, coronal condensation, coronal magnetic fields, and magnetic activity.

A cofounder of coronal loop theory, Dr. Antiochos developed the first numerical model of a coronal loop. He 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. One of his most important contributions is his model of cool loops to explain the structure of the lower transition region, a model that has inspired a great deal of observational research.

One of the long-standing puzzles in solar physics 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 SOHO and TRACE observations demonstrate 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 spawned 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 has 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 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.

In another seminal contribution, Dr. Antiochos developed a "breakout" model for the initiation of coronal mass ejections. 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 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 current sheet formation and magnetic reconnection, work that is now finding application in laboratory plasmas, as well.

Dr. Antiochos credits these advances to his collaborations at NRL, noting, "Whatever successes I may have had are, in large part, due to my colleagues in the Solar Theory Section and the Laboratory for Computational Physics. Their expertise in solar theory, computational methods, and data analysis and interpretation was essential for originating and developing new models of solar activity. I believe that the opportunity for senior researchers to work together as a close-knit team that encompasses a comprehensive range of expertise is the greatest strength of NRL."

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.

Dr. Antiochos is a member of the American Physical Society, the International Astronomical Union, the AAS, and the AGU. From 1991 to 1993, he served as chair of the AAS Solar Physics Division (SPD). 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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