2004 ASTRONOMY & ASTROPHYSICS - Indian Academy of Sciences

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CHAPTER 3 Solar Physics Introduction The Sun is a unique astrophysical laboratory which has revealed fundamental information that has had a significant impact on physics. Indeed the subject of Astrophysics began with an attempt to understand the spectrum of the Sun. During the last century, many deep insights were obtained by trying to understand various phenomena related to the Sun. Very recently the resolution of the solar neutrino puzzle has contributed to verifying a major new idea in elementary particle physics. In addition, the Sun has been a prototype for stars in general. Being the nearest star, observations of the Sun reveal details one can never hope to see in the distant stars. Precisely because of the richness of the data, it has been a major challenge to understand the complexities of the Sun such as its internal structure, rotation, convection, magnetic fields, activity and explosive processes in its outer atmosphere. Indian astronomers and physicists have pursued research in solar physics for more than a century The Solar Observatory at Kodaikanal now, and their impact has been noteworthy. Historically, India has been the central stage for some of the important discoveries. The total solar eclipse in August, 1868 attracted many teams of astronomers from around the world. One of them, the French astronomer Jansen demonstrated that solar prominences can be observed even without a total eclipse of the Sun. Pogson of the Madras Observatory made the fundamental discovery that the spectral lines of the hydrogen atom are seen in emission during totality. One of the emission lines in the flash spectrum was identified as arising due to a new element which was called Helium (later to be isolated and identified on the earth). A few years later, in 1893, a committee chaired by Lord Kelvin decided to establish a solar observatory in Kodaikanal. The observatory started functioning in 1901, with Michie Smith as the Director. A few years later Evershed joined the observatory, and in 1909 made the historic discovery of radial motion in sunspots, a phenomenon now known as the Evershed effect. Solar physics continued to flourish at the Kodaikanal Observatory and many significant contributions were John Evershed made during the first half of the 20 th century. These include: • Morphological studies of prominences, their distribution and their properties during the solar cycle; • Observations of solar activity and its relation to geomagnetic perturbations; 27
SOLAR PHYSICS • Detailed study of sunspots, including the observations of bright rings and bright streaks in the penumbra; • Observation of the corona during three major total solar eclipses. In the mid 1950s, a Solar Tower Telescope, equipped with a spectrograph was commissioned at Kodaikanal. This facility enabled high dispersion solar spectroscopy to be carried out at the observatory. During the next couple of decades a number of important contributions came from this observatory in the following areas: • Longitudinal distribution of sunspots • Study of magnetic and velocity oscillations in the photosphere • Studies of chromospheric structures • Solar-stellar connection • Luminosity variation of the Sun • Pole-ward migration of the filaments • Measurement of vector magnetic fields, etc. An important feature of this observatory was the synoptic observations of full disk white light photoheliograms, and also spectroheliograms in the H-alpha line of hydrogen and the K-line of calcium. Right from the beginning, the Kodaikanal observatory maintained an active exchange programme with the Royal Greenwich Observatory and the Mount Wilson Observatory for the “missing days” of observations. This has resulted in an impressive collection of almost uninterrupted synoptic observations of the Sun. For the first seventy years of the 20 th century, solar astronomy was essentially confined to Kodaikanal. This was to change in the 1970s. Solar observations began in the early 1970s at the newly established State Observatory in Nainital. A little later the Udaipur Solar Observatory was established. The Ooty Radio Telescope built and operated by the TIFR soon joined the area with its observations of the solar wind. Solar Physics in India – the current scene Today solar astronomy is being pursued at a number of observatories, research institutes and university departments: • The Indian Institute of Astrophysics, Bangalore • Physical Research Laboratory, Ahmedabad • Tata Institute of Fundamental Research, Mumbai The Solar Tower Telescope at Kodaikanal 28
Page 1 and 2: ASTRONOMY & ASTROPHYSICS A Decadal
Page 3 and 4: This publication of the Academy on
Page 5 and 6: Preface The Indian Academy of Scien
Page 7 and 8: The Academy Committee for Astronomy
Page 9 and 10: h e P a n e l s Theoretical Astroph
Page 11 and 12: C H A P T E R 1 Executive Summary
Page 13 and 14: EXECUTIVE SUMMARY The recommendatio
Page 15 and 16: EXECUTIVE SUMMARY feasibility study
Page 17 and 18: C H A P T E R 2 The Present Revolut
Page 19 and 20: THE PRESENT REVOLUTION IN ASTRONOMY
Page 37: A large eruptive prominence in HeII
Page 41 and 42: SOLAR PHYSICS Nainital Observatory
Page 43 and 44: SOLAR PHYSICS Some Possible New Ini
Page 45 and 46: SOLAR PHYSICS Telescope and the Hel
Page 47 and 48: C H A P T E R 4 Optical, Infrared &
Page 49 and 50: OPTICAL, INFRARED & ULTRAVIOLET AST
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Page 71 and 72: RADIO ASTRONOMY India’s location
Page 73 and 74: RADIO ASTRONOMY The first telescope
Page 75 and 76: RADIO ASTRONOMY Central Electronic
Page 77 and 78: RADIO ASTRONOMY • Resolution of t
Page 79 and 80: RADIO ASTRONOMY Some recommendation
Page 81 and 82: C H A P T E R 6 High Energy Astrono
Page 83 and 84: HIGH ENERGY ASTRONOMY 100 cm 2 area
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HIGH ENERGY ASTRONOMY detectors, an
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HIGH ENERGY ASTRONOMY Gamma Ray Ast
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HIGH ENERGY ASTRONOMY A gamma ray b
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HIGH ENERGY ASTRONOMY Cosmic Rays T
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HIGH ENERGY ASTRONOMY from Hyderaba
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HIGH ENERGY ASTRONOMY • Solar con
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HIGH ENERGY ASTRONOMY nuclear compo
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HIGH ENERGY ASTRONOMY New initiativ
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C H A P T E R Theoretical Astrophys
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THEORETICAL ASTROPHYSICS • The di
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THEORETICAL ASTROPHYSICS There has
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THEORETICAL ASTROPHYSICS 5. Equatio
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C H A P T E R Gravitation and Parti
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GRAVITATION AND PARTICLE ASTROPHYSI
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C H A P T E R Recommendations 9
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RECOMMENDATIONS different aspects s
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RECOMMENDATIONS was installed there
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RECOMMENDATIONS Keeping in mind the
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RECOMMENDATIONS The 1 m telescope a
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RECOMMENDATIONS as the technology t
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RECOMMENDATIONS The committee appre
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RECOMMENDATIONS • All Sky Monitor
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RECOMMENDATIONS using our facilitie
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RECOMMENDATIONS • The committee s
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List of addresses Radio Observatori
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S.N. Bose National Centre for Basic
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Indian Academy of Sciences C. V. Ra
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2004 ASTRONOMY & ASTROPHYSICS - Indian Academy of Sciences

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