Detalles de publicación
PP 07040
Quiet Sun Magnetic Field Measurements Based on Lines with Hyperfine Structure
((1) Instituto de Astrofisica de Canarias, La Laguna, Spain,
(2) Dipartimento di Fisica, Universita di Roma Tor Vergata, Rome, Italy,
(3) Universita degli Studi di Firenze, Dipartimento di Astronomia e
Scienza dello Spazio, Firenze, Italy)
The Zeeman pattern of MnI lines is sensitive to
hyperfine structure (HFS) and, they respond to hG magnetic
field strengths differently from the lines used in solar
magnetometry. This peculiarity has been employed
to measure magnetic field strengths in quiet Sun
regions. However, the methods applied so far assume the
magnetic field to be constant in the resolution element.
The assumption is clearly insufficient to describe the
complex quiet Sun magnetic fields, biasing the results of
the measurements. We present the first syntheses
of MnI lines in realistic quiet Sun model atmospheres.
The syntheses show how the MnI lines weaken with
increasing field strength. In particular, kG magnetic
concentrations produce NnI 5538 circular polarization signals
(Stokes V) which can be up to two orders of magnitude smaller
than the weak magnetic field approximation prediction. Consequently,
(1) the polarization emerging from an atmosphere having weak
and strong fields is biased towards the weak fields, and
(2) HFS features characteristic of weak fields show up even when
the magnetic flux and energy are dominated by kG fields.
For the HFS feature of MnI 5538 to disappear the filling factor
of kG fields has to be larger than the filling factor of sub-kG
fields. Stokes V depends on magnetic field inclination according
to the simple consine law. Atmospheres with unresolved velocities
produce asymmetric line profiles, which cannot be reproduced by
simple one-component model atmospheres. The uncertainty of the HFS
constants do not limit the use of MnI lines for magnetometry.
hyperfine structure (HFS) and, they respond to hG magnetic
field strengths differently from the lines used in solar
magnetometry. This peculiarity has been employed
to measure magnetic field strengths in quiet Sun
regions. However, the methods applied so far assume the
magnetic field to be constant in the resolution element.
The assumption is clearly insufficient to describe the
complex quiet Sun magnetic fields, biasing the results of
the measurements. We present the first syntheses
of MnI lines in realistic quiet Sun model atmospheres.
The syntheses show how the MnI lines weaken with
increasing field strength. In particular, kG magnetic
concentrations produce NnI 5538 circular polarization signals
(Stokes V) which can be up to two orders of magnitude smaller
than the weak magnetic field approximation prediction. Consequently,
(1) the polarization emerging from an atmosphere having weak
and strong fields is biased towards the weak fields, and
(2) HFS features characteristic of weak fields show up even when
the magnetic flux and energy are dominated by kG fields.
For the HFS feature of MnI 5538 to disappear the filling factor
of kG fields has to be larger than the filling factor of sub-kG
fields. Stokes V depends on magnetic field inclination according
to the simple consine law. Atmospheres with unresolved velocities
produce asymmetric line profiles, which cannot be reproduced by
simple one-component model atmospheres. The uncertainty of the HFS
constants do not limit the use of MnI lines for magnetometry.