Sigma Xi Seminar Series
Sponsored by Sigma Xi: The Scientific Research Honor Society
Presents:
Total Solar Eclipses:
Opportunities to Investigate
the Cold Heart of the Solar Atmosphere
by
Dr. T. Alan Clark,
Professor Emeritus, Department of Physics and Astronomy, University of Calgary
Thursday, September 21rd 2017, 5 pm
University of Calgary, Biological Sciences Room 211
Annual General Meeting
Abstract: Total solar eclipses have fascinated and frightened people for centuries. However, for scientists in the past 150 years, they have provided unique opportunities for the study of regions of the Sun’s outer atmosphere that are normally hidden in the glare of sunlight. This talk will outline the basic geometry of an eclipse and review the source and transfer of energy within the Sun before discussing one of the most persistent problems still facing solar physicists, the existence of extremely high gas temperatures in the tenuous layers of the solar atmosphere beyond a distinct temperature minimum just above the visible photosphere. This will be followed by an illustrated summary of the work of the Calgary group in defining the parameters of this temperature minimum, including the calibrated determination of the solar gas temperature using infra-red solar spectroscopy from high-altitude balloon-borne telescopes and the determination of the precise height of this layer using measurements of eclipses from jet aircraft and mountain-altitude observatories. Of interest in this work has been observations of carbon monoxide, CO, a gas that should not survive at the expected temperature in this minimum region but which exists in a persistent layer overlying the Sun’s photosphere. The talk will conclude with a summary of possible heating mechanisms that might produce the observed temperature structure.
Bio: Alan Clark, Professor Emeritus in the Department of Physics and Astronomy, obtained his in Physics at the University of Leeds in 1963, spent the next three years in Calgary studying the aurora using balloon-borne X-ray detectors and then moved to University College London to assist in the initiation a programme of balloon-borne astronomy. In 1970, he returned to Calgary and helped to guide the initial development of the University of Calgary’s Rothney Observatory. Later, as Co-Director, he supervised the design, and installation of several telescopes. He developed a research in solar physics and subsequently used high-altitude balloons and jet aircraft to carry instrumentation above the Earth’s absorbing atmosphere and mountain-top observatory telescopes to study the solar atmosphere. He was an award-winning teacher at the university and, along with two colleagues, has written several editions of a textbook that provides exercises in astronomy using the Starry Night planetarium program.
We also wish to acknowledge the Department of Biological Sciences which has provided the venue