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\newpage{Hal Zirin's Research Interests}
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	Zirins interests center around all aspects of solar physics, particularly the
	dynamics and evolution of magnetic active regions and solar flares, and the
	structure of the chromosphere and corona. \p
	
	The Sun is the only star we can learn a great deal about, and Caltech 
	possesses the best and most comprehensive facilities in the world for its 
	study. Big Bear Solar Observatory (BBSO) resides in the middle of Big Bear 
	Lake, in the San Bernadino mountains two hours from Caltech, to solve the 
	special problems of solar observing. Because of the excellent seeing and 
	transparency there, unique high-resolution observations are routinely carried
	out. An array of optical telescopes, ranging in size and including a 26-inch
	reflector, are available at BBSO for solar observations, along with three 0.25 A
	bandpass birefringent filters and an array of other instruments. 
	Particularly important is the videomagnetograph, which was an developed
	at Caltech and allows the observation in real time of small-scale magnetic
	features on the solar surface. For the first time in history we can watch small
	magnetic dipoles emerge, move around, reconnect and cancel, and from
	these observations, we hope to learn more about the magnetohydrodynamics
	of the solar surface. \p
	
	A vector magnetograph has been developed to examine the three-dimensional
	structure of the solar magnetic fields. With this it has been possible to record
	the changes of magnetic fields associated with the occurrence of solar flares.
	A second instrument, called thespectromagnetograph, has been developed to
	eliminate uncertainty over filling factors in solar fields. It is the only existing
	instrument with which the true field strength outside of sunspots can be
	directly determined. \p
	
	Another aspect of the study of magnetic fields has been the study of the
	magnetic cycle. The observatory follows the fields close to the pole of the Sun
	to watch and understand how the poles change with the solar cycle; another
	target is the actual rotation rate at the pole, which is still unknown.
	A new program using magneto-optic atomic resonance cells to measure field
	vectors and small scale flows on the solar surface was recently begun. \p
	
	Another telescope for solar research run by Caltech is the solar microwave 
	facility at Owens Valley, which consists of a pair of dedicated 27-meter 
	parabolic antennas, each equipped with a frequency-agile receiver capable 
	of observing between 1 and 18 GHz. These are used with four smaller dishes
	to produce maps and spectra of the synchrotron emission from solar flares. 
	This is one of the best ways to observe the acceleration of solar particles in
	flares. Interferometry provides high spatial resolution and suppresses
	background signal for high S/N observations of solar flares and active
	regions. A third antenna, 40-meters in diameter, is available about 20
	days/year for solar observations, and with the third dish our spatial
	resolution increases to better than 2 arcseconds at 18 GHz. \p
	
	By superposing the radio maps on the Big Bear images, we can determine
	the magnetic configurations in which particles are accelerated, and explore
	the mysterious mechanisms by which the acceleration is carried out. \p
	
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	Some recent references: \p
	
	\i{Ap.J.}, \b{329}, 991, 1988 (with D. Gary), 
	``Microwave Structure of the Quiet Sun." \p
	
	\i{Ap.J.}, \b{329}, 991, 1988 (with D. Gary), 
	Cambridge University Press, 1988, ``Astrophysics of the Sun." \p
	
	\i{Solar Physics}, \b{125}, 45, 1990 (with H. Wang).
	``Flows, Flares, Formation of Umbrae and Light Bridges in BBSO Region #1167." \p
	
	\i{Solar Physics}, \b{144}, 37, 1993 (with H. Wang), 
	``Strong Transverse Fields in Delta Spots." \p
	
	\i{Astrophysical Journal}, \b{403}, 426, 1993, 
	(with M.W. Ewell, J. B. Jensen and T. S. Bastian), 
	``Submillimeter Observations of the 11 July 1991 Total Solar Eclipse" \p
	
	\i{Solar Physics}, \b{144}, 37, 1993, (with H. Wang), 
	``Strong Transverse Fields in Delta Spots" \p
	
	\i{Proc. IAU Colloquium No. 141}, Astr Soc. Pac Conference 
	series No. 46, 1993 (with Guoxiang Ai, and H. Wang), 
	``The Magnetic and Velocity Fields of Solar Active Regions." \p
	
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