| 1. |
- Seta, Takamasa, et al.
(author)
-
Pressure broadening coefficients of the water vapor lines at 556.936 and 752.033 GHz
- 2008
-
In: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0273-1177 .- 0022-4073. ; 109:1, s. 144-150
-
Journal article (peer-reviewed)abstract
- The air induced broadening coefficients of the pure rotational transitions of H2O at 556.936 GHz (110←101), and 752.033 GHz (211←202) were measured by terahertz time-domain spectroscopy. The air broadening coefficient was determined to be for the 556.936 GHz line and for the 752.033 GHz line, respectively. The present broadening coefficients for the 556.936 GHz water line are significantly smaller than those of Markov and Krupnov [Measurements of the pressure shift of the 1(10)–1(01) water line at 556.936 GHz produced by mixtures of gases. J Mol Spect 1995:172;211–4] but relatively close to the values of the HITRAN database. The measured data may improve the accuracy of the abundance of water vapor retrieved from spectra obtained by the Odin/SMR satellite instrument. The effect on the satellite retrieval processing is discussed.
|
|
| 2. |
- Björn, Lars Olof, et al.
(author)
-
Evolution of UV-B regulation and protection in plants
- 2002
-
In: Advances in Space Research. - 1879-1948 .- 0273-1177. ; 30:6, s. 1557-1562
-
Conference paper (peer-reviewed)abstract
- Plants have evolved under the influence of UV-B radiation and have acquired systems for monitoring it and investing appropriate resources for protection against it, i.e., filters, quenchers of radicals and reactive oxygen species, and repair systems. An hypothesis for how plants monitor radiation has been presented.
|
|
| 3. |
- Borges, F O, et al.
(author)
-
Weighted oscillator strengths and lifetimes for the SVII spectrum
- 2004
-
In: Journal of Quantitative Spectroscopy & Radiative Transfer. - 0022-4073. ; 83:3-4, s. 751-763
-
Journal article (peer-reviewed)abstract
- The weighted oscillator strengths (gf) and the lifetimes presented in this work were carried out in a multiconfiguration Hartree-Fock relativistic approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure, in order to improve the adjustment to experimental energy levels. This method produces gf-values that are in better agreement with intensity observations and lifetime values that are closer to the experimental ones. In this work, we presented all the experimentally known electric dipole S VII spectral lines.
|
|
| 4. |
- Sikström, Carl Martin, et al.
(author)
-
Uncertainty of oscillator strengths derived from lifetimes and branching fractions
- 2002
-
In: Journal of Quantitative Spectroscopy and Radiative Transfer. - 0022-4073. ; 74:3, s. 355-368
-
Journal article (peer-reviewed)abstract
- A widely used method for determination of transition probabilities and oscillator strengths is based on measurements of branching fractions and radiative lifetimes. In the present work the different sources of uncertainty in branching fraction measurements using Fourier transform spectroscopy and lifetime measurements using laser induced fluorescence are discussed. A detailed description is presented of how the uncertainties should be combined to provide a well-defined uncertainty of the derived quantity. Finally, an example shows how the individual uncertainties can be presented in an "uncertainty budget".
|
|
| 5. |
- Axner, Ove, et al.
(author)
-
A general non-complex analytical expression for the nth Fourier component of a wavelength-modulated Lorentzian lineshape function
- 2001
-
In: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier. - 0022-4073 .- 1879-1352. ; 68:3, s. 299-317
-
Journal article (peer-reviewed)abstract
- A general, analytical expression for the nth Fourier component of a wavelength-modulated Lorentzian lineshape function in terms of a normalized detuning and a normalized modulation amplitude is derived. The expression is cast in a purely real form and is therefore easier to use than the normally used expression, which is given in terms of various combinations (sums, square roots, and powers) of complex expressions and their complex conjugates. Analytical expressions for the nine first Fourier components (n = 0,...,8), clearly showing their dependence on normalized detuning and modulation amplitude, are explicitly given. Simplified expressions for the even harmonics of the Fourier components on resonance, at which they take their maximum value, solely given in terms of the normalized modulation amplitude, are also explicitly given. It is shown that previously published, numerically calculated conditions for maximization of higher-order Fourier components are incorrect. The normalized modulation amplitudes that maximize the four lowest even harmonics of the Fourier components, i.e. for n = 2, 4, 6, and 8, are 2.20, 4.12, 6.08, and 8.06, respectively.
|
|
| 6. |
- Bohm, Martin, et al.
(author)
-
Dynamic trapping of electrons in the porcupine ionospheric ion beam experiment
- 1992
-
In: Advances in Space Research. - 0273-1177. ; 12, s. 9-14
-
Journal article (peer-reviewed)abstract
- Electrons are needed to maintain quasineutrality in a case where positive ions are injected across the magnetic field into a limited volume in a magnetized plasma. In the absence of collisions, a positive potential builds up and traps the electrons which enter the region along the magnetic field. If the added density of ions exceeds the ambient density, large potential differences along the magnetic field can be maintained this way. The process explains several features of the Porcupine xenon ion beam injection experiment, where strong magnetic-field-aligned electric fields were measured in the vicinity of a xenon ion beam which was injected into the ambient ionosphere from a spinning subpayload. © 1992.
|
|
| 7. |
- Brenning, Nils, et al.
(author)
-
Critical ionization velocity interaction in the CRIT I rocket experiment
- 1990
-
In: Advances in Space Research. - : Elsevier BV. - 0273-1177. ; 10, s. 63-66
-
Journal article (peer-reviewed)abstract
- In the rocket experiment CRIT I, launched from Wallops Island on 13 May 1986, two identical Barium shaped charges were fired from distances of 1.3 km and 3.6 km towards the main experiment payload, which was separated from a sub-payload by a couple of km along the magnetic field. The relevance of earlier proposed mechanisms for electron heating in ionospheric critical velocity experiments is investigated in the light of the CRIT I results. It is concluded that both the "homogeneous" and the "ionizing front" models can be applied, in different parts of the stream. It is also possible that a third, entirely different, mechanism may contribute to the electron heating. This mechanism involves direct energization of electrons in the magnetic-field-aligned component of the DC electric field. © 1989.
|
|
| 8. |
- Brenning, Nils, et al.
(author)
-
Electrodynamic interaction between the CRIT I ionized barium streams and the ambient ionosphere
- 1990
-
In: Advances in Space Research. - : Elsevier BV. - 0273-1177. ; 10, s. 67-70
-
Journal article (peer-reviewed)abstract
- In the CRIT I Critical Velocity experiment, launched from Wallops Island on 13 May, 1986, two fast barium streams were ejected by means of shaped charges. Their electrodynamic interaction with the ambient ionosphere is discussed. An outstanding feature of the DC electric field observed within the streams was a large magnetic-field-aligned component, persisting on the time scale of the passage of the streams. One interpretation of the DC electric field data is that the internal electric fields of the streams is not greatly modified by Birkeland currents, i.e. a state is established, where the transverse currents are to a first approximation divergence-free. It is argued that this interpretation can explain why a reversal of the strong explosion-directed electric field was observed in the first explosion but not in the second (more distant one). © 1989.
|
|
| 9. |
|
|
| 10. |
- Eriksson, Patrick, et al.
(author)
-
A Hotelling transformation approach for rapid inversion of atmospheric spectra
- 2002
-
In: Journal of Quantitative Spectroscopy and Radiative Transfer. - 0022-4073 .- 1879-1352. ; 73:6, s. 529-543
-
Journal article (peer-reviewed)abstract
- Atmospheric observations from space often result in spectral data of large dimensions. To allow an optimal inversion of the observed spectra it can be necessary to map the data into a space of smaller dimension. Here several data reduction techniques based on eigenvector expansions of the spectral space are compared. The comparison is done by inverting simulated observations from a microwave limb sounder, the Odin-SMR. For the examples tested, reductions exceeding two orders of magnitude with no negative influence on the retrieval performance are demonstrated. The techniques compared include a novel method developed especially for atmospheric inversions, based on the weighting functions of the variables to be retrieved. The new method shows an excellent performance in practical tests and is both computationally more effective and more flexible than the standard Hotelling transformation.
|
|
