On the inversion of the scattering polarization and the Hanle effect signals in the hydrogen Lyα line

Journal Article · Sun Jun 01 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/787/2/159· OSTI ID:22356727

Ishikawa, R. ^[1]; Asensio Ramos, A.; Manso Sainz, R.; Trujillo Bueno, J. ^[2]; Belluzzi, L. ^[3]; Štěpán, J. ^[4]; Goto, M. ^[5]

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1. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
2. Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain)
3. Istituto Ricerche Solari Locarno (IRSOL), via Patocchi, 6605 Locarno Monti (Switzerland)
4. Astronomical Institute of the Academy of Sciences, Fričova 298, 251 65 Ondřejov (Czech Republic)
5. National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292 (Japan)

Magnetic field measurements in the upper chromosphere and above, where the gas-to-magnetic pressure ratio β is lower than unity, are essential for understanding the thermal structure and dynamical activity of the solar atmosphere. Recent developments in the theory and numerical modeling of polarization in spectral lines have suggested that information on the magnetic field of the chromosphere-corona transition region could be obtained by measuring the linear polarization of the solar disk radiation at the core of the hydrogen Lyα line at 121.6 nm, which is produced by scattering processes and the Hanle effect. The Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) sounding rocket experiment aims to measure the intensity (Stokes I) and the linear polarization profiles (Q/I and U/I) of the hydrogen Lyα line. In this paper, we clarify the information that the Hanle effect can provide by applying a Stokes inversion technique based on a database search. The database contains all theoretical Q/I and U/I profiles calculated in a one-dimensional semi-empirical model of the solar atmosphere for all possible values of the strength, inclination, and azimuth of the magnetic field vector, though this atmospheric region is highly inhomogeneous and dynamic. We focus on understanding the sensitivity of the inversion results to the noise and spectral resolution of the synthetic observations as well as the ambiguities and limitation inherent to the Hanle effect when only the hydrogen Lyα is used. We conclude that spectropolarimetric observations with CLASP can indeed be a suitable diagnostic tool for probing the magnetism of the transition region, especially when complemented with information on the magnetic field azimuth that can be obtained from other instruments.

• OSTI ID: 22356727
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 787; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CHROMOSPHERE
HYDROGEN
INCLINATION
LYMAN LINES
MAGNETIC FIELDS
NOISE
ONE-DIMENSIONAL CALCULATIONS
POLARIMETERS
POLARIZATION
RESOLUTION
SCATTERING
SENSITIVITY
SOUND WAVES
SPACE DEPENDENCE
SPECTROSCOPY
SUN
ULTRAVIOLET RADIATION