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  • 1
    Electronic Resource
    Electronic Resource
    Enhanced incoherent scatter plasma lines (1997)
    Springer
    Annales geophysicae 14 (1997), S. 1462-1472 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Detailed model calculations of auroral secondary and photoelectron distributions for varying conditions have been used to calculate the theoretical enhancement of incoherent scatter plasma lines. These calculations are compared with EISCAT UHF radar measurements of enhanced plasma lines from both the E and F regions, and published EISCAT VHP radar measurements. The agreement between the calculated and observed plasma line enhancements is good. The enhancement from the superthermal distribution can explain even the very strong enhancements observed in the auroral E region during aurora, as previously shown by Kirk-wood et al. The model calculations are used to predict the range of conditions when enhanced plasma lines will be seen with the existing high-latitude incoherent scatter radars, including the new EISCAT Svalbard radar. It is found that the detailed structure, i.e. the gradients in the suprathermal distribution, are most important for the plasma line enhancement. The level of superthermal flux affects the enhancement only in the region of low phase energy where the number of thermal electrons is comparable to the number of suprathermal electrons and in the region of high phase energy where the suprathermal fluxes fall to such low levels that their effect becomes small compared to the collision term. To facilitate the use of the predictions for the different radars, the expected signal-to-noise ratios (SNRs) for typical plasma line enhancements have been calculated. It is found that the high-frequency radars (Søndre Strømfjord, EISCAT UHF) should observe the highest SNR, but only for rather high plasma frequencies. The VHP radars (EISCAT VHP and Svalbard) will detect enhanced plasma lines over a wider range of frequencies, but with lower SNR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-996-1462-z
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  • 2
    Electronic Resource
    Electronic Resource
    Proton-electron precipitation effects on the electron production and density above EISCAT (Tromsø) and ESR (1998)
    Springer
    Annales geophysicae 16 (1998), S. 1299-1307 
    Details
    ISSN: 0992-7689
    Keywords: Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions; particle precipitation).
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The suprathermal particles, electrons and protons, coming from the Sun and precipitating into the high-latitude atmosphere are an energy source for the Earth’s ionosphere. They interact with the ambient thermal gas through inelastic and elastic collisions. Most of the physical quantities perturbed by the precipitation, such as the electron production rate, may be evaluated by solving the stationary Boltzmann transport equation, which yields the particle fluxes as a function of altitude, energy, and pitch angle. This equation has been solved for the three different suprathermal species (electrons, protons and hydrogen atoms). We first compare the results of our theoretical code to a coordinated DMSP/EISCAT experiment, and to another approach. Then, we show the effects that pure proton precipitation may have on the ionosphere, through primary and secondary ionization. Finally, we compare the effects of proton precipitation and electron precipitation in some selected cases above EISCAT (Tromsó) and ESR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-998-1299-8
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Proton transport model in the ionosphere. 2. Influence of magnetic mirroring and collisions on the angular redistribution in a proton beam (1998)
    Springer
    Annales geophysicae 16 (1998), S. 1308-1321 
    Details
    ISSN: 0992-7689
    Keywords: Auroral ionosphere ; Particle precipitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We investigate the influence of magnetic mirroring and elastic and inelastic scattering on the angular redistribution in a proton/hydrogen beam by using a transport code in comparison with observations. H-emission Doppler profiles viewed in the magnetic zenith exhibit a red-shifted component which is indicative of upward fluxes. In order to determine the origin of this red shift, we evaluate the influence of two angular redistribution sources which are included in our proton/hydrogen transport model. Even though it generates an upward flux, the redistribution due to magnetic mirroring effect is not sufficient to explain the red shift. On the other hand, the collisional angular scattering induces a much more significant red shift in the lower atmosphere. The red shift due to collisions is produced by 〈 1 -keV protons and is so small as to require an instrumental bandwidth 〈0.2nm. This explains the absence of measured upward proton/hydrogen fluxes in the Proton I rocket data because no useable data concerning protons 〈 1 keV are available. At the same time, our model agrees with measured ground-based H-emission Doppler profiles and suggests that previously reported red shift observations were due mostly to instrumental bandwidth broadening of the profile. Our results suggest that Doppler profile measurements with higher spectral resolution may enable us to quantify better the angular scattering in proton aurora.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-998-1308-y
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  • 4
    Electronic Resource
    Electronic Resource
    Benzene exposure in car mechanics and road tanker drivers (1998)
    Springer
    International archives of occupational and environmental health 71 (1998), S. 277-283 
    Details
    ISSN: 1432-1246
    Keywords: Key words Benzene exposure ; Car mechanics ; Road tanker drivers ; Unleaded petrol ; trans ; trans-Muconic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this study was to identify professional factors related to benzene exposure and to deduce suitable safety measures. Atmospheric benzene, urinary muconic acid (tt-MA) and leukocyte alkaline phosphatase activity (LAPA) were evaluated among 66 car mechanics, 34 road tanker drivers, and 28 nonexposed workers. Professional and medical questionnaires were filled in at the same time. Atmospheric benzene was significantly higher among road tanker drivers than among car mechanics. The arithmetic mean ± SD, median, and geometric mean values were, respectively, 0.48 ± 1.49, 0.14, and 0.06 mg/m3 among car mechanics and 1.88 ± 4.18, 0.68, and 0.65 mg/m3 among road tanker drivers. In the latter case the increase was caused by transport of unleaded petrol and correlated with the volume of the tank. Among car mechanics, tobacco smoking, windy conditions, dismantling of petrol filters, and handling of petrol increased atmospheric benzene levels. Urinary muconic acid was increased significantly among car mechanics (148 ± 137, 127, and 111 μg/g) and among road tanker drivers (309 ± 420, 137, and 151 μg/g) as compared with the controls (49 ± 46, 33, and 33 μg/g). Among road tanker drivers, alcohol intake and transportation of unleaded petrol increased the excretion of muconic acid, which was also directly related to the volume of the tank. Among car mechanics, professional factors (dismantling of petrol filters, handling of and washing of hands with petrol) and nonprofessional factors (tobacco smoking and damaged skin on the hands and forearms) increased muconic acid excretion. In the control group, tobacco smoking increased its excretion. LAPA was not significantly modified among exposed workers. There was a weak but significant linear correlation between LAPA and muconic acid. These results suggest that to reduce exposure to benzene in unleaded petrol, individual and collective safety measures should be imposed in both occupations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004200050281
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    Paper (German National Licenses)
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