A treatment of the Zeeman effect using Stokes formalism and its implementation in the Atmospheric Radiative Transfer Simulator (ARTS)

Larsson, Richard; Buehler, Stefan A.; Eriksson, Patrick; Mendrok, Jana

doi:10.1016/j.jqsrt.2013.09.006

Cited by 37 publications

(43 citation statements)

References 27 publications

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“…The radiation of Zeeman split spectral lines can be described with the radiative transfer equation in the following form (Larsson et al 2014):…”

Section: Analysis Methodsmentioning

confidence: 99%

“…In addition, we developed the Zeeman splitting extension ZRAD that takes the Zeeman splitting and polarization of spectral lines into account. The implementation of the Zeeman splitting is based on the works of Landi Degl'Innocenti (1976), Schadee (1978), Rees et al (1989), and Larsson et al (2014). For each considered Zeeman split spectral line, ZRAD requires the following pre-calculated quantities:…”

Section: Radiative Transfermentioning

confidence: 99%

“…For the line shape, ZRAD includes natural, collisional, and Doppler broadening mechanisms (line shape: Voigt profile) as well as the magneto-optic effect (line shape: Faraday-Voigt profile, Larsson et al 2014). The Voigt and Faraday-Voigt profiles are obtained from the real and imaginary part of the Faddeeva function, respectively (Wells 1999).…”

Section: Radiative Transfermentioning

confidence: 99%

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Magnetic fields in molecular clouds: Limitations of the analysis of Zeeman observations

Brauer

Wolf

Reißl

et al. 2017

A&A

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Context. Observations of Zeeman split spectral lines represent an important approach to derive the structure and strength of magnetic fields in molecular clouds. In contrast to the uncertainty of the spectral line observation itself, the uncertainty of the analysis method to derive the magnetic field strength from these observations is not been well characterized so far. Aims. We investigate the impact of several physical quantities on the uncertainty of the analysis method, which is used to derive the line-of-sight (LOS) magnetic field strength from Zeeman split spectral lines. These quantities are the density, temperature, velocity, and the magnetic field strength. Methods. We simulate the Zeeman splitting of the 1665 MHz OH line with the 3D radiative transfer (RT) extension ZRAD. This extension is based on the line RT code Mol3D (Ober et al. 2015) and has been developed for the POLArized RadIation Simulator POLARIS . Results. Observations of the OH Zeeman effect in typical molecular clouds are not significantly affected by the uncertainty of the analysis method. However, some observations obtained a magnetic field strength of more than ∼300 µG, which may result in an uncertainty of the analysis method of >10%. We derived an approximation to quantify the range of parameters in which the analysis method works sufficiently accurate and provide factors to convert our results to other spectral lines and species as well. We applied these conversion factors to CN and found that observations of the CN Zeeman effect in typical molecular clouds are neither significantly affected by the uncertainty of the analysis method. In addition, we found that the density has almost no impact on the uncertainty of the analysis method, unless it reaches values higher than those typically found in molecular clouds (n H 10 7 cm −3 ). Furthermore, the uncertainty of the analysis method increases, if both the gas velocity and the magnetic field show significant variations along the line-of-sight. However, this increase should be small in Zeeman observations of most molecular clouds considering typical velocities of ∼1 km/s.

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“…The radiation of Zeeman split spectral lines can be described with the radiative transfer equation in the following form (Larsson et al 2014):…”

Section: Analysis Methodsmentioning

confidence: 99%

Section: Radiative Transfermentioning

confidence: 99%

Section: Radiative Transfermentioning

confidence: 99%

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Magnetic fields in molecular clouds: Limitations of the analysis of Zeeman observations

Brauer

Wolf

Reißl

et al. 2017

A&A

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“…This radiation will have its circular polarization state altered. The implementation and the physics of the Zeeman effect in ARTS are described in detail by Larsson et al (2014) and Larsson (2014) and references therein.…”

Section: Zeeman Effectmentioning

confidence: 99%

“…The implementation of this effect uses a Stokes vector formalism where the extinction term in the scalar radiative transfer equation is replaced by a four-by-four propagation matrix. This has benefited greatly from the experience gathered with the last important addition that has to be mentioned here: the capability to simulate oxygen Zeeman splitting in a physically rigorous way, which is also handled by a Stokes vector formalism, described in Larsson et al (2014) and Larsson (2014). The method has been validated against observations in uplooking (Navas- Guzmán et al, 2015) and down-looking (Larsson et al, 2016) geometry and has also already been employed for some sensitivity and retrieval simulation studies (Larsson et al, 2013(Larsson et al, , 2017.…”

Section: Introductionmentioning

confidence: 99%

ARTS, the Atmospheric Radiative Transfer Simulator – version 2.2, the planetary toolbox edition

Buehler¹,

Mendrok²,

Eriksson³

et al. 2018

Geosci. Model Dev.

Self Cite

143

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Abstract. This article describes the latest stable release (version 2.2) of the Atmospheric Radiative Transfer Simulator (ARTS), a public domain software for radiative transfer simulations in the thermal spectral range (microwave to infrared). The main feature of this release is a planetary toolbox that allows simulations for the planets Venus, Mars, and Jupiter, in addition to Earth. This required considerable model adaptations, most notably in the area of gaseous absorption calculations. Other new features are also described, notably radio link budgets (including the effect of Faraday rotation that changes the polarization state) and the treatment of Zeeman splitting for oxygen spectral lines. The latter is relevant, for example, for the various operational microwave satellite temperature sensors of the Advanced Microwave Sounding Unit (AMSU) family.

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Microwave hyperspectral measurements for temperature and humidity atmospheric profiling from satellite: The clear‐sky case

et al. 2015

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This study investigates the benefits of a satellite HYperspectral Microwave Sensor (HYMS) for the retrieval of atmospheric temperature and humidity profiles, in the context of numerical weather prediction (NWP). In the infrared, hyperspectral instruments have already improved the accuracy of NWP forecasts. Microwave instruments so far only provide observations for a limited number of carefully selected channels. An information content analysis is conducted here to assess the impact of hyperspectral microwave measurements on the retrieval of temperature and water vapor profiles under clear‐sky conditions. It uses radiative transfer simulations over a large variety of atmospheric situations. It accounts for realistic observation (instrument and radiative transfer) noise and for a priori information assumptions compatible with NWP practices. The estimated retrieval performance of the HYMS instrument is compared to those of the microwave instruments to be deployed on board the future generation of European operational meteorological satellites (MetOp‐SG). The results confirm the positive impact of a HYMS instrument on the atmospheric profiling capabilities compared to MetOp‐SG. Temperature retrieval uncertainty, compared to a priori information, is reduced by 2 to 10%, depending on the atmospheric height, and improvement rates are much higher than what will be obtained with MetOp‐SG. For humidity sounding these improvements can reach 30%, a significant benefit as compared to MetOp‐SG results especially below 250 hPa. The results are not very sensitive to the instrument noise, under our assumptions. The main impact provided by the hyperspectral information originates from the higher resolution in the O2 band around 60 GHz. The results are presented over ocean at nadir, but similar conclusions are obtained for other incidence angles and over land.

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A treatment of the Zeeman effect using Stokes formalism and its implementation in the Atmospheric Radiative Transfer Simulator (ARTS)

Cited by 37 publications

References 27 publications

Magnetic fields in molecular clouds: Limitations of the analysis of Zeeman observations

Magnetic fields in molecular clouds: Limitations of the analysis of Zeeman observations

ARTS, the Atmospheric Radiative Transfer Simulator – version 2.2, the planetary toolbox edition

Microwave hyperspectral measurements for temperature and humidity atmospheric profiling from satellite: The clear‐sky case

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