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  • 1
    Electronic Resource
    Electronic Resource
    The role played by thermal feedback in heated Farley-Buneman waves at high latitudes (2000)
    Springer
    Annales geophysicae 18 (2000), S. 532-546 
    Details
    ISSN: 0992-7689
    Keywords: Ionosphere (auroral ionosphere; ionospheric irregularities; plasma waves and instabilities)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract It is becoming increasingly clear that electron thermal effects have to be taken into account when dealing with the theory of ionospheric instabilities in the high-latitude ionosphere. Unfortunately, the mathematical complexity often hides the physical processes at work. We follow the limiting cases of a complex but systematic generalized fluid approach to get to the heart of the thermal processes that affect the stability of E region waves during electron heating events. We try to show as simply as possible under what conditions thermal effects contribute to the destabilization of strongly field-aligned (zero aspect angle) Farley-Buneman modes. We show that destabilization can arise from a combination of (1) a reduction in pressure gradients associated with temperature fluctuations that are out of phase with density fluctuations, and (2) thermal diffusion, which takes the electrons from regions of enhanced temperatures to regions of negative temperature fluctuations, and therefore enhanced densities. However, we also show that, contrary to what has been suggested in the past, for modes excited along the E0 × B direction thermal feedback decreases the growth rate and raises the threshold speed of the Farley-Buneman instability. The increase in threshold speed appears to be important enough to explain the generation of ‘Type IV’ waves in the high-latitude ionosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-000-0532-x
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  • 2
    Electronic Resource
    Electronic Resource
    Nonlinear model of short-scale electrodynamics in the auroral ionosphere (2000)
    Springer
    Annales geophysicae 18 (2000), S. 1128-1144 
    Details
    ISSN: 0992-7689
    Keywords: Ionosphere (auroral ionosphere, electric fields and currents, ionosphere-magnetosphere interactions)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The optical detection of auroral subarcs a few tens of m wide as well as the direct observation of shears several m/s per m over km to sub km scales by rocket instrumentation both indicate that violent and highly localized electrodynamics can occur at times in the auroral ionosphere over scales 100 m or less in width. These observations as well as the detection of unstable ion-acoustic waves observed by incoherent radars along the geomagnetic field lines has motivated us to develop a detailed time-dependent two-dimensional model of short-scale auroral electrodynamics that uses current continuity, Ohm’s law, and 8-moment transport equations for the ions and electrons in the presence of large ambient electric fields to describe wide auroral arcs with sharp edges in response to sharp cut-offs in precipitation (even though it may be possible to describe thin arcs and ultra-thin arcs with our model, we have left such a study for future work). We present the essential elements of this new model and illustrate the model’s usefulness with a sample run for which the ambient electric field is 100 mV/m away from the arc and for which electron precipitation cuts off over a region 100 m wide. The sample run demonstrates that parallel current densities of the order of several hundred μA m-2 can be triggered in these circumstances, together with shears several m/s per m in magnitude and parallel electric fields of the order of 0.1 mV/m around 130 km altitude. It also illustrates that the local ionospheric properties like densities, temperature and composition can strongly be affected by the violent localized electrodynamics and vice-versa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-000-1128-1
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  • 3
    Electronic Resource
    Electronic Resource
    On the usefulness of E region electron temperatures and lower F region ion temperatures for the extraction of thermospheric parameters: a case study (1999)
    Springer
    Annales geophysicae 17 (1999), S. 1182-1198 
    Details
    ISSN: 0992-7689
    Keywords: Ionosphere (auroral ionosphere; ionosphere atmosphere interactions; plasma temperature and density)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Using EISCAT data, we have studied the behavior of the E region electron temperature and of the lower F region ion temperature during a period that was particularly active geomagnetically. We have found that the E region electron temperatures responded quite predictably to the effective electric field. For this reason, the E region electron temperature correlated well with the lower F region ion temperature. However, there were several instances during the period under study when the magnitude of the E region electron temperature response was much larger than expected from the ion temperature observations at higher altitudes. We discovered that these instances were related to very strong neutral winds in the 110–175 km altitude region. In one instance that was scrutinized in detail using E region ion drift measurement in conjunction with the temperature observations, we uncovered that, as suspected, the wind was moving in a direction closely matching that of the ions, strongly suggesting that ion drag was at work. In this particular instance the wind reached a magnitude of the order of 350 m/s at 115 km and of at least 750 m/s at 160 km altitude. Curiously enough, there was no indication of strong upper F region neutral winds at the time; this might have been because the event was uncovered around noon, at a time when, in the F region, the E × B drift was strongly westward but the pressure gradients strongly northward in the F region. Our study indicates that both the lower F region ion temperatures and the E region electron temperatures can be used to extract useful geophysical parameters such as the neutral density (through a determination of ion-neutral collision frequencies) and Joule heating rates (through the direct connection that we have confirmed exists between temperatures and the effective electric field).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-999-1182-2
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  • 4
    Electronic Resource
    Electronic Resource
    Electron thermal effects on the Farley–Buneman fluid dispersion relation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 1032-1055 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The traditional linear fluid dispersion relation of Farley–Buneman waves has been generalized by including, for the electron gas, the effects of collisional energy exchange, as well as thermal force and thermoelectric effects associated with heat flow. The formalism used is that of Schunk [Rev. Geophys. Space Phys. 15, 429 (1977)] for Grad's 8-moment approximation, to which inelastic energy exchange has been added phenomenologically. The resulting dispersion relation recovers both the traditional isothermal and adiabatic limits, as well as the dispersion relation of Pécseli et al. [J. Geophys. Res. 94, 5337 (1989)] as a special case. Owing to the fact that the electron–neutral interaction is far from being of the Maxwell molecule type, it is found that, contrary to suggestions in the literature, adiabaticity does not hold at the larger wavelengths of the instability. In the small wave-number limit, the linear instability threshold speed of the waves takes the form [(γeTe0+Ti0)/mi]1/2, with the effective γe being a sensitive function of aspect angle. Its value can be as small as 0.28 or as large as 3.4 depending on conditions. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871383
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  • 5
    Electronic Resource
    Electronic Resource
    Electron heating by plasma waves in the high latitude E-region and related effects: Observations
    Amsterdam : Elsevier
    Advances in Space Research 10 (1990), S. 225-237 
    Details
    ISSN: 0273-1177
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0273-1177(90)90256-Y
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  • 6
    Electronic Resource
    Electronic Resource
    Electron heating by plasma waves in the high latitude E-region and related effects: theory
    Amsterdam : Elsevier
    Advances in Space Research 10 (1990), S. 239-249 
    Details
    ISSN: 0273-1177
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0273-1177(90)90257-Z
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  • 7
    Electronic Resource
    Electronic Resource
    On a mechanism for the formation of VLF electrostatic emissions in the high latitude F-region
    Amsterdam : Elsevier
    Planetary and Space Science 26 (1978), S. 801-816 
    Details
    ISSN: 0032-0633
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0032-0633(78)90104-6
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  • 8
    Electronic Resource
    Electronic Resource
    Behaviour of ion velocity distributions for a simple collision model
    Amsterdam : Elsevier
    Planetary and Space Science 22 (1974), S. 1-18 
    Details
    ISSN: 0032-0633
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0032-0633(74)90119-6
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  • 9
    Electronic Resource
    Electronic Resource
    Auroral ion velocity distributions using a relaxation model
    Amsterdam : Elsevier
    Planetary and Space Science 21 (1973), S. 1115-1130 
    Details
    ISSN: 0032-0633
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0032-0633(73)90200-6
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  • 10
    Electronic Resource
    Electronic Resource
    Auroral ion velocity distributions for a polarization collision model
    Amsterdam : Elsevier
    Planetary and Space Science 25 (1977), S. 243-260 
    Details
    ISSN: 0032-0633
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0032-0633(77)90135-0
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