PROMISES AND PITFALLS OF SOLAR Hα ZEEMAN SPECTROPOLARIMETRY

摘要

Zeeman spectropolarimetry of the solar disk in the Hα line is a daunting, yet promising diagnostic for measuring solar chromospheric magnetic fields. As a demonstration of its potential we used the National Solar Observatory (NSO)/High Altitude Observatory (HAO) Advanced Stokes Polarimeter to obtain simultaneous measurements of polarimetric signals from the photosphere in the Fe Ⅰ 6301.5, 6302.5 A lines and from the chromosphere in Hα. With these measurements, we explore the promises and pitfalls of Hα Zeeman spectropolarimetry. Remarkable features observed in Hα include a reversal of Zeeman polarity in the emission core across flaring active regions and highly redshifted and smeared Stokes Ⅴ profiles in prominences. We reproduce the Hα Zeeman reversals using radiative transfer diagnostics, and we compare photospheric and chromospheric line-of-sight magnetic fields.