Bibcode
Trujilo-Bueno, J.; Ramelli, R.; Merenda, L.; Bianda, M.
Bibliographical reference
The Physics of Chromospheric Plasmas ASP Conference Series, Vol. 368, Proceedings of the conference held 9-13 October, 2006 at the University of Coimbra in Coimbra, Portugal. Edited by P. Heinzel, I. Dorotovič, and R. J. Rutten. San Francisco: Astronomical Society of the Pacific, 2007., p.161
Advertised on:
5
2007
Citations
0
Refereed citations
0
Description
A suitable diagnostic tool for investigating the magnetism of the solar
chromosphere is the observation and theoretical modeling of the Hanle
and Zeeman effects in solar spicules. In our presentation we highlighted
the great scientific interest of this new diagnostic window by showing
how the magnetic field vector can be inferred from spectropolarimetric
observations of solar chromospheric spicules in several spectral lines,
such as those of the 10830 Å and 5876 Å multiplets of
neutral helium. Our off-limb spectropolarimetric observations of the He
I 10830 Å multiplet were obtained with the Tenerife Infrared
Polarimeter (TIP) attached to the Vacuum Tower Telescope at the
Observatorio del Teide (Tenerife), while those of the 5876 Å
multiplet resulted from observations with the Zurich Imaging Polarimeter
(ZIMPOL) at the Gregory Coudé Telescope of the Istituto Ricerche
Solari Locarno. The application of a Stokes profiles inversion technique
led to the following conclusion. In quiet Sun spicules the magnetic
field vector at a height of about 2000 km above the solar visible
``surface" has a typical strength of the order to 10 G and is inclined
by approximately 35° with respect to the solar local vertical
direction. In spicules observed close to active regions the strength of
the magnetic field was of the order of 50 G. The two figures below show
the off-limb Stokes profiles of the He I 5876 Å multiplet observed
in a quiet region (upper figure) and close to an active region (lower
figure). Note that in both cases Stokes U is non-zero, which is the
observational signature of the Hanle effect of an inclined magnetic
field. The change of sign in Stokes U along the spatial direction of the
spectrograph's slit can be explained by variations in the azimuth of the
magnetic field vector. Interestingly, while the Stokes V profiles
corresponding to the observed quiet region are caused by the
alignment-to-orientation transfer mechanism (see, e.g., page 607 of
Landi Degl'Innocenti & Landolfi 2004), that observed in the spicules
close to the active region is dominated by the longitudinal Zeeman
effect. The interested reader will find more information in the papers
by Trujillo Bueno et al. (2005) and by Ramelli et al. (2006).