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  • 1
    Digitale Medien
    Digitale Medien
    High-latitude HF Doppler observations of ULF waves. 1. Waves with large spatial scale sizes (1997)
    Springer
    Annales geophysicae 15 (1997), S. 1548-1556 
    Details
    ISSN: 0992-7689
    Schlagwort(e): Auroral ionosphere ; Magnetosphere-ionosphere interactions ; MHD waves and instabilities HF Dopplre ; ULF Waves
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract A quantitative study of observations of the ionospheric signatures of magnetospheric ultra low frequency (ULF) waves by a high-latitude (geographic: 69.6°N 19.2°E) high-frequency Doppler sounder has been undertaken. The signatures, which are clearly correlated with pulsations in ground magnetometer data, exhibit periods in the range 100–400 s and have azimuthal wave numbers in the range 3–8. They are interpreted here as local field line resonances. Phase information provided by O- and X-mode Doppler data support the view that these are associated with field line resonances having large azimuthal scale sizes. The relative phases and amplitudes of the signatures in the Doppler and ground magnetometer data are compared with a model for the generation of Doppler signatures from incident ULF waves. The outcome suggests that the dominant mechanism involved in producing the Doppler signature is the vertical component of an E × B bulk motion of the local plasma caused by the electric field perturbation of the ULF wave.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s00585-997-1548-2
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    A comparison of EISCAT and HF Doppler observations of a ULF wave (1998)
    Springer
    Annales geophysicae 16 (1998), S. 1190-1199 
    Details
    ISSN: 0992-7689
    Schlagwort(e): Magnetosphere-ionosphere interactions ; MHD waves and instabilities ; Radio science ; Ionospheric physics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Since the middle of 1995, an HF Doppler sounder has been running almost continuously in northern Norway, with the receiver at Ramfjordmoen and the transmitter at Seljelvnes. Concurrent operation of the EISCAT UHF radar in common programme (CP-1) mode has made it possible to study the ionospheric signature of a magnetospheric ULF wave. These are the first results of such wave signatures observed simultaneously in both instruments. It has been demonstrated that the observed Doppler signature was mainly due to the vertical bulk motion of the ionosphere caused by the electric field perturbation of the ULF wave and the first direct observational confirmation of a numerical simulation has been achieved. The wave, which was Alfvénic in nature, was detected by the instruments 8° equatorward of the broad resonance region. The implications for the deduced wave modes in the ionosphere and the mechanism producing the HF Doppler variations are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s00585-998-1190-7
    Standort Signatur Erwartet Verfügbarkeit
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    Artikel (Nationallizenzen)
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  • 3
    Digitale Medien
    Digitale Medien
    Investigation and comparison of some models for removing ocular artefacts from EEG signals (1988)
    Springer
    Medical & biological engineering & computing 26 (1988), S. 584-590 
    Details
    ISSN: 1741-0444
    Schlagwort(e): Correlation ; EEG ; EOG ; Models ; Ocular artefacts
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract An investigation of ocular artefacts (OAs) in the human electroencephalogram (EEG) to quantify the effectiveness of OA removal and to find the most effective model for removing OAs online is described. In Part 1, the models used in the investigation are described and the data analysed. The analysis showed that the ‘true’ EEG exhibited a high degree of serial correlation and so the ordinary least-squares (OLS) method employed to remove OA was inefficient. Efficient alternative methods based on autoregressive models of the ‘true’ EEG are discussed. It is also shown that the EOGs are linearly dependent making some of them redundant. In Part 2, the models are compared.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02447495
    Standort Signatur Erwartet Verfügbarkeit
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    Artikel (Nationallizenzen)
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  • 4
    Digitale Medien
    Digitale Medien
    Investigation and comparison of some models for removing ocular artefacts from EEG signals (1988)
    Springer
    Medical & biological engineering & computing 26 (1988), S. 591-598 
    Details
    ISSN: 1741-0444
    Schlagwort(e): EEG ; EOG ; Model comparison ; Ocular artefacts removal
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract An investigation of ocular artefacts (OAs) in the human electroencephalogram (EEG) to quantify the effectiveness of OA removal, and to find the most effective model for removing OAs online is described. It was found unnecessary to use the vertical and horizontal EOGs of both eyes, although more than one EOG signal is required for adequate OA removal. The model using the vertical right EOG and the two horizontal EOGs was the best overall, but in most cases the use of only the vertical and horizontal right EOGs was sufficient. OAs were not completely removed by any of the models investigated, suggesting that more complex models are necessary.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02447496
    Standort Signatur Erwartet Verfügbarkeit
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    Artikel (Nationallizenzen)
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