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Zero-field dichroism in the solar chromosphere.
R Manso Sainz1, J Trujillo Bueno
1Instituto de Astrofísica de Canarias, Vía Láctea s/n, E-38205 La Laguna, Tenerife, Spain.
Physical Review Letters
|October 4, 2003
Summary
We explain the linear polarization of Ca II infrared triplet lines near the solar limb. Atomic polarization in lower levels causes differential absorption, explaining these enigmatic solar polarizations.
Area of Science:
- Solar Physics
- Atomic Physics
- Astrophysical Spectroscopy
Background:
- Linear polarization of the Ca II infrared triplet near the solar limb is observed but not fully understood.
- Previous models have not adequately explained the origin of these enigmatic polarization signals.
Purpose of the Study:
- To elucidate the physical origin of the linear polarization in the Ca II 866.2 nm and 854.2 nm lines.
- To investigate the role of atomic polarization in metastable lower levels and its effect on radiation transfer.
Main Methods:
- Solving the problem of polarized radiation generation and transfer.
- Fully accounting for optical pumping mechanisms in multilevel atomic models.
- Analyzing atomic polarization in metastable (2)D(3/2, 5/2) levels.
Main Results:
- Atomic polarization in the metastable (2)D(3/2, 5/2) lower levels is identified as the source of the observed polarization.
- This atomic polarization leads to differential absorption of polarization components (dichroism).
- The model successfully explains the enigmatic polarization of the Ca II 866.2 nm and 854.2 nm lines.
Conclusions:
- The physical origin of the enigmatic polarization of the Ca II infrared triplet lines is atomic polarization in their metastable lower levels.
- This phenomenon results in "zero-field" dichroism, which has significant diagnostic potential in astrophysics.
- The findings offer a new avenue for astrophysical diagnostics using polarized spectral lines.
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