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  • 1
    ISSN: 1573-2932
    Keywords: Acidification ; modelling ; nitrogen ; land-use ; MAGIC-WAND
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The Galloway region of Southwest Scotland has been subject to decades of acidic deposition which has resulted in damage to soils, surface waters and aquatic biota. A survey of lochs was conducted in 1979, 1988, and 1993, over which time there have been dramatic changes in total sulphur and nitrogen deposition. The MAGIC model successfully reproduced the major chemical changes in water chemistry from 1979 to 1988 during which time there was a rapid decline in sulphur deposition. A new coupled sulphur and nitrogen model (MAGIC-WAND) has been used to evaluate the regional hydrochemical response to changing patterns of N & S deposition from the period 1988 to 1993. Details of the model structure and parameterisation are discussed. The model under-predicts the response of non-marine sulphate in the region suggesting that there has been a slight increase in deposition over this period. Future hydrochemical responses to different nitrogen deposition scenarios are presented, indicating that the potential increase of nitrogen in surface waters is closely linked to the age and extent of different mosaics of commercial afforestation within the individual catchments.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 25 (1972), S. 197-209 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Type III solar noise bursts have been observed in the frequency range 25–100 kHz with the VLF detector on OGO 3. The bursts decrease in frequency from 100 kHz (the highest frequency of observation) to as low as 25 kHz in approximately 45 min. The intensity at 100 kHz increases for about 20 min then decays over a period of approximately 1 h. The variation of the intensity with time becomes less regular at lower frequencies. Observed maximum intensities near 80 kHz range from 3 × 10−18 to 2 × 10−16 W m−2 Hz−1. Bursts are predominantly associated with west-limb flares. Their commencement at 100 kHz tends to follow type III bursts observed at 2–4 MHz by about 10 min. Observed drift rates and decay times correspond roughly to those extrapolated from higher frequency measurements. Type III and the so-called ‘high-pass’ noise bursts often occur simultaneously, presenting a problem in identification. The solar noise events can be distinguished by their relatively slow time variation, smooth spectrum, and low intensity.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Ground-based VLF observations show evidence that strong whistler-mode waves in the magneto-sphere are often stimulated by harmonic radiation from electrical power transmission lines. These stimulated emissions sometimes dominate the wave activity in the kHz range. A VLF transmitter at Siple, Antarctica has been used to simulate these power line effects with ∼ 0.5 W radiated power at a given frequency. Occurrence statistics of power line effects are also summarized.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 15 (1974), S. 781-802 
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Whistler-mode waves injected into the magnetosphere from ground sources (e.g., lightning discharge, vlf transmitters) are used to probe the distribution of ions and electrons in the magnetosphere. They also cause wave growth (vlf emissions) and precipitation of electrons. Bursts of X-rays (〉 30 keV) and enhancements of D-region ionization are examples of precipitation effects caused by lightning-generated waves. Growing narrowband wave trains are triggered by manmade coherent waves. Growth rates of ∼ 100 dB s-1 and total growths up to 30 dB have been measured using 5.5 kHz signals transmitted from Siple Station, Antarctica. Another source of coherent wave input to the magnetosphere are the harmonics from commercial power line systems. Power line harmonic radiation may suppress triggered emissions or change their frequency-time slope. Exponential growth of narrowband emissions is explained in terms of cyclotron resonance between the waves and trapped energetic electrons, with feedback included. Applications of wave injection experiments include: (1) study of emission mechanisms, (2) control of energetic particle precipitation, (3) diagnostics of cold and hot plasma, and (4) vlf communications.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A CLOSE correlation has been discovered in the times of occurrence of very low frequency and extra low frequency electromagnetic phenomena observed at high-latitude conjugate locations. The observations were carried out jointly by the Pacific Naval Laboratory of the Defence Research Board of Canada ...
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  • 7
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Detailed measurements of the pulse shape, spectrum, and pitch angle distribution of LEP events have not previously been obtained nor have direct satellite or ground-based measurements of LEP events been obtained within the plasmasphere where most VLF whistler activity occurs9. The plasmasphere ...
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 195 (1962), S. 64-65 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We agree that this interpretation is entirely consistent with the data reported in our article. As a matter of fact, further study of the original tape recordings has shown additional noise bursts which can be fitted into a repetitive or echo pattern, in which the phase is opposite at the two ends ...
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 187 (1960), S. 751-753 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] OBSERVATIONS during 1959 at Byrd Station, \J Antarctica (lat. 70-5 S. geomagnetic), show a close association to exist between aurorse and certain very low-frequency hiss. The hiss usually occurs in a broad band with a centre-frequency of about 8 kc./s. The intensity and band-width vary with ...
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  • 10
    Publication Date: 2011-08-19
    Description: Highlights of recent Stanford University VLF research in the Antarctic include new observations of wave-induced particle precipitation and controlled experiments on nonlinear wave growth phenomena. Higher-than-expected levels of burst precipitation have been discovered inside the plasmasphere, near L = 2, using subionospheric signal perturbations called 'Trimpi events'. Studies of burst precipitation have been extended to the region poleward of the plasmapause using the Siple transmitter signal as a waveguide probe. Experiments on the 'coherent wave instability', using the amplitude and frequency modulation capability of the new Siple transmitter, have produced exciting new results. Examples are: (1) better definition of the power threshold for the stimulation of temporal wave growth, (2) generation of strong sidebands by unamplified 'beat' waves and (3) generation of chorus-like elements within a band of simulated hiss. Using a new digital processing technique developed at Stanford, new features of the phase behavior of growing waves have been found. Opportunities for extending these experiments are discussed.
    Keywords: GEOPHYSICS
    Type: National Institute of Polar Research, Memoirs, Special Issue (ISSN 0386-0744); 38, D; 83-98
    Format: text
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