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Advanced Stokes Polarimeter Available for User...(1Jun93)
Community
(from NSO, NOAO Newsletter No. 34, 1 June 1993)

The Advanced Stokes Polarimeter (ASP), developed by the High Altitude
Observatory, NCAR, in a joint program with NSO/Sacramento Peak, was installed
at NSO's Vacuum Tower Telescope in March of last year. It is designed to
provide previously unattainable information about the magnetic structure and
evolution of sunspots and active regions, magnetic activity during the growth
and decay of solar flares, and the nature of flux tubes.

The ASP has provided the first high-angular-resolution, quantitative
measurements of the strength and direction of the magnetic field, at several
heights in the solar atmosphere. The three high-speed cameras (five arrays
total) each acquire 60 images per second, while the optical system compensates
for image motion. Initial runs of the ASP have produced quantitative
information with unprecedented resolution. It has already provided new
information on the structure of the magnetic field in and around sunspots. A
small sunspot revealed a penumbra threaded by "spines" of higher field strength
and greater vertical alignment than the background penumbral field, while the
magnetic field outside the sunspot showed a primarily vertical orientation.

The ASP is now available for use by visiting observers. Observing proposals for
its use should be submitted to the NSO/SP TAC. HAO scientists and engineers can
provide some guidance and assistance in ASP operation, data reduction and
analysis.

                         [figure not included]

Figure Caption: This image was recorded with the Advanced Stokes Polarimeter
used at the NSO/SP Vacuum Tower Telescope for magnetic field measurements of
a sunspot with high sensitivity. Shown here is the magnitude of the
line-of-sight field. Other images are available to illustrate the magnitude
and orientation of the transverse field.  Such observations will provide
previously unattainable information about the magnetic structure and evolution
of sunspots and active regions, magnetic activity during the growth and decay
of solar flares, and the nature of flux tubes.

Bruce Lites, Kim Streander,
David Elmore, Ray Smartt

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