The Hanle Effect and the Determination of Magnetic Fields

1979 ◽  
Vol 44 ◽  
pp. 87-91 ◽  
Author(s):  
V. Bommier ◽  
S. Sahal-Bréchot
Keyword(s):  
Magnetic Fields ◽  
Linear Polarization ◽  
Optical Pumping ◽  
Polarization Vector ◽  
Resonance Scattering ◽  
Incident Radiation ◽  
Research Area ◽  
Spectral Lines ◽  
Hanle Effect

A new research area has recently been developed in solar physics, i.e. the determination of magnetic fields by means of the interpretation of the two measured parameters describing the linear polarization of spectral lines (Leroy et al., 1977, Sahal-Bréchot et al., 1977, Leroy 1977a, b, 1978, Stenflo 1977, 1978, Sahal-Bréchot and Bommier 1977, Bommier and Sahal-Bréchot 1978). In solar prominences, this linear polarization is due to resonance scattering of the incident radiation field; the effect of the magnetic field B (Hanle effect) leads to a rotation of the polarization vector and a decrease of the degree of linear polarization. Both these parameters do depend on the strength and the direction of B and the dependence may be calculated using the theory of quantum optics and optical pumping.

scholarly journals A Determination of Magnetic Fields of T Tau and Ae/Be Herbig Stars Using the Parameters of Their Linear Polarization

1986 ◽  
Vol 90 ◽  
pp. 87-90
Author(s):  
Yu.N. Gnedin ◽  
M.A. Pogodin ◽  
N.P. Red’kina
Keyword(s):  
Magnetic Fields ◽  
Linear Polarization ◽  
Polarization Spectra ◽  
T Tau

AbstractAttempts of applying stellar polarization spectra to evaluation of magnetic fields of some types of stars are described.

scholarly journals Convective cells in Betelgeuse: imaging through spectropolarimetry

2018 ◽  
Vol 620 ◽  
pp. A199 ◽  
Author(s):  
A. López Ariste ◽  
P. Mathias ◽  
B. Tessore ◽  
A. Lèbre ◽  
M. Aurière ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Linear Polarization ◽  
Rayleigh Scattering ◽  
Characteristic Size ◽  
Spectral Lines ◽  
Stellar Disk ◽  
Convective Structures ◽  
Weak Magnetic Fields ◽  
Red Supergiants ◽  
Convective Cells

Aims. We assess the ability to image the photosphere of red supergiants and, in particular Betelgeuse, through the modelling of the observed linear polarization in atomic spectral lines. We also aim to analyse the resulting images over time, to measure the size and dynamics of the convective structures in these stars. Methods. Rayleigh scattering polarizes the continuum and spectral lines depolarize it. This depolarization is seen as a linear polarization signal parallel to the radial direction on the stellar disk. Integrated over the disk, it would result in a null signal, except if brightness asymmetries/inhomogeneities are present. This is the basic concept behind our imaging technique. Through several tests and comparisons, we have tried to assess and extend its validity, and to determine what can be learnt unambiguously through it. Results. The several tests and comparisons performed prove that our technique reliably retrieves the salient brightness structures in the photosphere of Betelgeuse, and should be relevant to other red supergiants. For Betelgeuse, we demonstrate that these structures we infer are convective cells, with a characteristic size of more than 60% of the stellar radius. We also derive the characteristic upflow and downflow speeds, 22 and 10 km s−1, respectively. We find weak magnetic fields concentrated in the downflow lanes in between granules, similar to the quiet sun magnetism. We follow those convective structures in time. Changes happen on timescales of 1 week, but individual structures can be tracked over 4 yr of observations. Conclusions. The measured characteristics of the convection in Betelgeuse confirm the predictions of numerical simulations in both the strong, supersonic upflows and the size of the convective cells. They also concur in the presence of weak magnetic fields that are completely dominated by the convective flows and constrained to the dark lanes of down-flowing plasma.

scholarly journals Inferring telescope polarization properties through spectral lines without linear polarization

2018 ◽  
Vol 615 ◽  
pp. A22 ◽  
Author(s):  
A. Derks ◽  
C. Beck ◽  
V. Martínez Pillet
Keyword(s):  
Linear Polarization ◽  
Input Data ◽  
Polarization State ◽  
Active Regions ◽  
Spectral Lines ◽  
Solar Telescope ◽  
Promising Tool ◽  
Visible Part ◽  
Telescope Optics

Context. Polarimetric observations taken with ground- or space-based telescopes usually need to be corrected for changes of the polarization state in the optical path. Aims. We present a technique to determine the polarization properties of a telescope through observations of spectral lines that have no or negligible intrinsic linear polarization signals. For such spectral lines, any observed linear polarization must be induced by the telescope optics. We apply the technique to observations taken with the Spectropolarimeter for Infrared and Optical Regions (SPINOR) at the Dunn Solar Telescope (DST) and demonstrate that we can retrieve the characteristic polarization properties of the DST at three wavelengths of 459, 526, and 615 nm. Methods. We determine the amount of crosstalk between the intensity Stokes I and the linear and circular polarization states Stokes Q, U, and V, and between Stokes V and Stokes Q and U in spectropolarimetric observations of active regions. We fit a set of parameters that describe the polarization properties of the DST to the observed crosstalk values. We compare our results to parameters that were derived using a conventional telescope calibration unit (TCU). Results. The values for the ratio of reflectivities X = rs∕rp and the retardance τ of the DST turret mirrors from the analysis of the crosstalk match those derived with the TCU within the error bars. We find a negligible contribution of retardance from the entrance and exit windows of the evacuated part of the DST. Residual crosstalk after applying a correction for the telescope polarization stays at a level of 3–10% regardless of which parameter set is used, but with an rms fluctuation in the input data of already a few percent. The accuracy in the determination of the telescope properties is thus more limited by the quality of the input data than the method itself. Conclusions. It is possible to derive the parameters that describe the polarization properties of a telescope from observations of spectral lines without intrinsic linear polarization signal. Such spectral lines have a dense coverage (about 50 nm separation) in the visible part of the spectrum (400–615 nm), but none were found at longer wavelengths. Using spectral lines without intrinsic linear polarization is a promising tool for the polarimetric calibration of current or future solar telescopes such as the Daniel K. Inouye Solar Telescope (DKIST).

An Operator Perturbation Method of Polarized Line Transfer V. Diagnosis of Solar Weak Magnetic Fields

2000 ◽  
Vol 179 ◽  
pp. 255-258
Author(s):  
K. N. Nagendra ◽  
H. Frisch ◽  
M. Faurobert-Scholl ◽  
F. Paletou
Keyword(s):  
Magnetic Fields ◽  
Perturbation Method ◽  
Solar Atmosphere ◽  
Iteration Method ◽  
Resonance Scattering ◽  
Spectral Lines ◽  
Perturbation Approach ◽  
Weak Magnetic Fields ◽  
Line Transfer

AbstractWe present an application of the PALI (Polarized Approximate Lambda Iteration) method to the resonance scattering in spectral lines formed in the presence of weak magnetic fields. The method is based on an operator perturbation approach, and can efficiently give solutions for oriented vector magnetic fields in the solar atmosphere.

scholarly journals Einfluß eines homogenen Magnetfeldes auf die Polarisation von Fluoreszenzlinien des Cu I-Spektrums nach Elektron enstoßanregung/ Influence of a homogeneous magnetic field on the polarization of fluorescence lines of the Cu I-spectrum induced by electron bombardment

1970 ◽  
Vol 25 (11) ◽  
pp. 1529-1536 ◽  
Author(s):  
G. Anger ◽  
M.V. Hartrott ◽  
H.-U. Martyn ◽  
G.v. Oppen
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Resonance Scattering ◽  
Homogeneous Magnetic Field ◽  
Electron Bombardment ◽  
Spectral Lines ◽  
Coupling Constants ◽  
Polarization Of Fluorescence

AbstractUsing atomic beam techniques the polarization of fluorescence lines of the Cu I-spectrum was measured in dependence on magnetic field strength. The Cu-atoms were excited by electron bombardment and the magnetic field was parallel to the electron beam. Due to the decoupling of the hyperfinestructure of excited levels of the Cu I-spectrum the polarization of some observed spectral lines [3247 Å (4p 2P3/2 -4s 2S1/2); 5153 Å (4d 2D3/2 -4p 2P1/2); 5218 Å (4d2D5/2 - 4p 2P3/2)] increases with increasing magnetic field strength. These polarization measurements, which correspond to investigations on resonance scattering of light done by HEYDENBURG et al., can be used for a determination of hfs-coupling constants of excited states. The measurements on the 3247 Å-resonance line are used for a comparison with results of accurate level-crossing-experiments. Satisfactory agreement is obtained. The discussion of the polarization of the 5153 Å-line yields an A-factor of (9.6 ± 1-0) MHz and a lifetime of τ ≈1.7 · 10 -8 sec for the 4d2D3/2-level.

scholarly journals Исследования конденсата поляритонов в микрорезонаторных микростолбиках в сильных магнитных полях -=SUP=-*-=/SUP=-

2018 ◽  
Vol 52 (1) ◽  
pp. 10
Author(s):  
А.В. Черненко ◽  
А.С. Бричкин ◽  
С.И. Новиков ◽  
К. Шнайдер ◽  
С. Хёфлинг
Keyword(s):  
Pump Power ◽  
Magnetic Fields ◽  
Linear Polarization ◽  
Optical Pumping ◽  
Zeeman Splitting ◽  
Laser Pulses ◽  
Considerable Effect ◽  
Nanosecond Laser ◽  
Wide Range ◽  
Linearly Polarized

AbstractThe photoluminescence of a nonequilibrium polariton condensate in cylindrical and rectangular micropillars etched on the surface of a high- Q GaAs microcavity is investigated in magnetic fields of up to 12 T. The measurements are carried out under different levels of nonresonant optical pumping with nanosecond laser pulses for a wide range of cavity detuning. As far as nonresonant excitation produces a high density of excitons in a reservoir, it should be expected that the exciton–polariton interaction, which depends on the pump level, has a considerable effect on the Zeeman splitting and polarization of the condensate. However, measurements of the Zeeman splitting and polarization in high magnetic fields demonstrate that only minor changes take place up to the highest available pump levels. This means that, in the case under study, the effect of exciton–polariton interaction on the polariton system is insignificant. At the same time, the data obtained provide an estimate for the exciton density in the reservoir. In contrast to cylindrical micropillars, the photoluminescence of the condensate in rectangular micropillars consists of two perpendicularly linearly polarized lines which retain a high degree of linear polarization even in a field as high as 12 T. The Zeeman splitting in this case is nearly independent of the pump power. The degrees of both circular and linear polarization change with pump power, but these changes are noticeably smaller than the ones predicted theoretically. This indicates that the system of polaritons in micropillars deviates considerably from thermodynamic equilibrium.

Resonanzstreuung von Licht an freien Ba+-Ionen

1966 ◽  
Vol 21 (5) ◽  
pp. 654-656 ◽  
Author(s):  
H. Bucka ◽  
J. Eichler ◽  
G. v. Oppen
Keyword(s):  
Magnetic Fields ◽  
Resonance Scattering ◽  
Hanle Effect

Resonance scattering on Ba+-ions of the 4554 Å-line (6 2P3/2—6 2S1/2) of the Ba II-spectrum was observed at various magnetic fields. Measuring the change of polarisation degree (HANLE effect) the lifetime of the 6 2P3/2-term was deduced to be (0.70 ± 0.06) × 10-8 sec.

The Interpretation of Line Profiles

1977 ◽  
Vol 36 ◽  
pp. 191-215
Author(s):  
G.B. Rybicki
Keyword(s):  
Magnetic Fields ◽  
Atomic Physics ◽  
Velocity Fields ◽  
Spectral Lines ◽  
Inhomogeneous Structure ◽  
The Sun ◽  
Line Profiles ◽  
Physical Phenomena

Observations of the shapes and intensities of spectral lines provide a bounty of information about the outer layers of the sun. In order to utilize this information, however, one is faced with a seemingly monumental task. The sun’s chromosphere and corona are extremely complex, and the underlying physical phenomena are far from being understood. Velocity fields, magnetic fields, Inhomogeneous structure, hydromagnetic phenomena – these are some of the complications that must be faced. Other uncertainties involve the atomic physics upon which all of the deductions depend.

Optimal Density Determination of Bouguer Anomaly Using Fractal Analysis (Case of study: Charak area,IRAN)

2005 ◽  
Vol 1 (1) ◽  
pp. 21-24
Author(s):  
Hamid Reza Samadi
Keyword(s):  
Surface Roughness ◽  
Fractal Dimension ◽  
Fractal Analysis ◽  
Fractal Geometry ◽  
Host Rock ◽  
Bouguer Anomaly ◽  
Research Area ◽  
Density Difference ◽  
Optimal Density

In exploration geophysics the main and initial aim is to determine density of under-research goals which have certain density difference with the host rock. Therefore, we state a method in this paper to determine the density of bouguer plate, the so-called variogram method based on fractal geometry. This method is based on minimizing surface roughness of bouguer anomaly. The fractal dimension of surface has been used as surface roughness of bouguer anomaly. Using this method, the optimal density of Charak area insouth of Hormozgan province can be determined which is 2/7 g/cfor the under-research area. This determined density has been used to correct and investigate its results about the isostasy of the studied area and results well-coincided with the geology of the area and dug exploratory holes in the text area

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