FABRY-PEROT VERSUS SLIT SPECTROPOLARIMETRY OF PORES AND ACTIVE NETWORK: ANALYSIS OF IBIS AND HINODE DATA

Journal Article · Sat Feb 20 00:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/710/2/1486· OSTI ID:21394426

Judge, Philip G; De Wijn, Alfred ^[1]; Tritschler, Alexandra; Uitenbroek, Han ^[2]; Reardon, Kevin; Cauzzi, Gianna ^[3]

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1. High Altitude Observatory, National Center for Atmospheric Research , P.O. Box 3000, Boulder, CO 80307-3000 (United States)
2. National Solar Observatory/Sacramento Peak , P.O. Box 62, Sunspot, NM 88349 (United States)
3. INAF-Ossevatorio Astrofisico di Arcetri, I-50125 Firenze (Italy)

We discuss spectropolarimetric measurements of photospheric (Fe I 630.25 nm) and chromospheric (Ca II 854.21 nm) spectral lines in and around small magnetic flux concentrations, including a pore. Our long-term goal is to diagnose properties of the magnetic field near the base of the corona. We compare ground-based two-dimensional spectropolarimetric measurem ents with (almost) simultaneous space-based slit spectropolarimetry. We address the question of noise and crosstalk in the measurements and attempt to determine the suitability of Ca II measurements with imaging spectropolarimeters for the determination of chromospheric magnetic fields. The ground-based observations were obtained 2008 May 20, with the Interferometric Bidimensional Spectrometer (IBIS) in spectropolarimetric mode operated at the Dunn Solar Telescope at Sunspot, NM. The space observations were obtained with the Spectro-Polarimeter of the Solar Optical Telescope aboard the Japanese Hinode satellite. The agreement between the near-simultaneous co-spatial IBIS and Hinode Stokes-V profiles at 630.25 nm is excellent, with V/I amplitudes compatible to within 1%. The IBIS QU measurements are affected by residual crosstalk from V, arising from calibration inaccuracies, not from any inherent limitation of imaging spectroscopy. We use a Principal Component Analysis to quantify the detected crosstalk. QU profiles with V crosstalk subtracted are in good agreement with the Hinode measurements, but are noisier owing to fewer collected photons. Chromospheric magnetic fields are notoriously difficult to constrain by polarization of Ca II lines alone. However, we demonstrate that high cadence, high angular resolution monochromatic images of fibrils in Ca II and Halpha, seen clearly in IBIS observations, can be used to improve the magnetic field constraints, under conditions of high electrical conductivity. Such work is possible only with time series data sets from two-dimensional spectroscopic instruments such as IBIS, under conditions of good seeing.

• OSTI ID: 21394426
• Journal Information: Astrophysical Journal, Vol. 710, Issue 2; Other Information: DOI: 10.1088/0004-637X/710/2/1486; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
AMPLITUDES
CALIBRATION
CHROMOSPHERE
ELECTRIC CONDUCTIVITY
INTERFEROMETERS
MAGNETIC FIELDS
MAGNETIC FLUX
MAGNETISM
MONOCHROMATIC RADIATION
NETWORK ANALYSIS
PHOTONS
PHOTOSPHERE
POLARIMETERS
POLARIZATION
SATELLITES
SPECTROMETERS
SPECTROSCOPY
SUN
SUNSPOTS
TELESCOPES
ATMOSPHERES
BOSONS
ELECTRICAL PROPERTIES
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
MAIN SEQUENCE STARS
MASSLESS PARTICLES
MEASURING INSTRUMENTS
PHYSICAL PROPERTIES
RADIATIONS
SOLAR ACTIVITY
SOLAR ATMOSPHERE
STARS
STARSPOTS
STELLAR ACTIVITY
STELLAR ATMOSPHERES