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  • 1
    Electronic Resource
    Electronic Resource
    New electron energy transfer and cooling rates by excitation of O2 (1998)
    Springer
    Annales geophysicae 16 (1998), S. 1007-1013 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In this work I present the results of a study of the electron cooling rate, the production rates of vibrationally excited O2, and the production frequency of the O2 vibrational quanta arising from the collisions of electrons with O2 molecules as functions of the electron temperature. The electron energy transfer and cooling rates by vibrational excitation of O2 have been calculated and fitted to analytical expressions by use of the revised vibrationally excited O2 cross sections. These new analytical expressions are available to the researcher for quick reference and accurate computer modeling with a minimum of calculations. It is also shown that the currently accepted rate of electron energy loss associated with rotational transitions in O2 must be decreased by a factor of 13.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-998-1007-8
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  • 2
    Electronic Resource
    Electronic Resource
    The role of vibrationally excited oxygen and nitrogen in the ionosphere during the undisturbed and geomagnetic storm period of 6–12 April 1990 (1998)
    Springer
    Annales geophysicae 16 (1998), S. 589-601 
    Details
    ISSN: 0992-7689
    Keywords: Ion chemistry and composition ; Ionosphere – atmosphere interactions ; Ionospheric disturbances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We present a comparison of the observed behavior of the F-region ionosphere over Millstone Hill during the geomagnetically quiet and storm periods of 6–12 April 1990 with numerical model calculations from the IZMIRAN time-dependent mathematical model of the Earth’s ionosphere and plasmasphere. The major enhancement to the IZMIRAN model developed in this study is the use of a new loss rate of O+(4S) ions as a result of new high-temperature flowing afterglow measurements of the rate coefficients K1 and K2 for the reactions of O+(4S) with N2 and O2. The deviations from the Boltzmann distribution for the first five vibrational levels of O2(v) were calculated, and the present study suggests that these deviations are not significant. It was found that the difference between the non-Boltzmann and Boltzmann distribution assumptions of O2(v) and the difference between ion and neutral temperature can lead to an increase of up to about 3% or a decrease of up to about 4% of the calculated NmF2 as a result of a respective increase or a decrease in K2. The IZMIRAN model reproduces major features of the data. We found that the inclusion of vibrationally excited N2(v 〉 0) and O2(v 〉 0) in the calculations improves the agreement between the calculated NmF2 and the data on 6, 9, and 10 April. However, both the daytime and nighttime densities are reproduced by the IZMIRAN model without the vibrationally excited nitrogen and oxygen on 8 and 11 April better than the IZMIRAN model with N2(v 〉 0) and O2(v 〉 0). This could be due to possible uncertainties in model neutral temperature and densities, EUV fluxes, rate coefficients, and the flow of ionization between the ionosphere and plasmasphere, and possible horizontal divergence of the flux of ionization above the station. Our calculations show that the increase in the O+ + N2 rate factor due to N2(v 〉 0) produces a 5–36% decrease in the calculated daytime peak density. The increase in the O+ + O2 loss rate due to vibrationally excited O2 produces 8–46% reductions in NmF2. The effects of vibrationally excited O2 and N2 on Ne and Te are most pronounced during the daytime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-998-0589-5
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  • 3
    Electronic Resource
    Electronic Resource
    Correlations between SAR arc intensity and solar and geomagnetic activity (1999)
    Springer
    Annales geophysicae 17 (1999), S. 770-781 
    Details
    ISSN: 0992-7689
    Keywords: Atmospheric composition and structure (airglow and aurora) ; Ionosphere (ionosphere-atmosphere interactions; ionosphere-magnetosphere interactions)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We present a study of statistical relationships between SAR arc intensities acquired by the Pacific Northwest Laboratory Photometer Network during 1978–1988 and solar and geomagnetic activity indices Dst, F10.7, and Kp by use of the method of multiple regression analysis. We found significant correlations between intensity and all of the indices involved. In the present work we show for the first time that the partial correlation coefficients depend on the time offset, t, between the time of SAR arc intensity observations and the onset of the geomagnetic storm recovery phase, with the largest correlations being observed when 8 d t d 16 h. It is also shown that there are significant differences between partial correlation coefficients calculated for SAR arcs associated with strong (Dstmin 〉 −100 nT) and weak (Dstmin 〉 −100 nT) geomagnetic storms. We observe also that the multiple correlation coefficients for strong storms are much larger than for weak ones. We found that the variations in the electron temperature, Te, in the SAR arc region are not mainly produced by variations in the electron density of the ionosphere but are strongly driven by the additional heating of the electron gas due to an interaction of the ring current ions and the plasmaspheric electrons. As a result, variations of Te in the SAR arc region with characteristic time scales from several minutes to several hours are stipulated by time variations of ring current parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-999-0770-5
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  • 4
    Electronic Resource
    Electronic Resource
    The role of vibrationally excited nitrogen and oxygen in the ionosphere over Millstone Hill during 16-23 March, 1990 (2000)
    Springer
    Annales geophysicae 18 (2000), S. 957-966 
    Details
    ISSN: 0992-7689
    Keywords: Ionosphere (ion chemistry and composition; ionosphere-atmosphere interactions; ionospheric disturbances)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We present a comparison of the observed behavior of the F region ionosphere over Millstone Hill during the geomagnetically quiet and storm period on 16/23 March, 1990, with numerical model calculations from the time-dependent mathematical model of the Earth’s ionosphere and plasmasphere. The effects of vibrationally excited N2(v) and O2(v) on the electron density and temperature are studied using the N2(v) and O2(v) Boltzmann and non-Boltzmann distribution assumptions. The deviations from the Boltzmann distribution for the first five vibrational levels of N2(v) and O2(v) were calculated. The present study suggests that these deviations are not significant at vibrational levels v = 1 and 2, and the calculated distributions of N2(v) and O2(v) are highly non-Boltzmann at vibrational levels v 〉 2. The N2(v) and O2(v) non-Boltzmann distribution assumption leads to the decrease of the calculated daytime NmF2 up to a factor of 1.44 (maximum value) in comparison with the N2(v) and O2(v) Boltzmann distribution assumption. The resulting effects of N2(v 〉 0) and O2(v) 〉 0) on the NmF2 is the decrease of the calculated daytime NmF2 up to a factor of 2.8 (maximum value) for Boltzmann populations of N2(v) and O2(v) and up to a factor of 3.5 (maximum value) for non-Boltzmann populations of N2(v) and O2(v). This decrease in electron density results in the increase of the calculated daytime electron temperature up to about 1040/1410 K (maximum value) at the F2 peak altitude giving closer agreement between the measured and modeled electron temperatures. Both the daytime and nighttime densities are not reproduced by the model without N2(v 〉 0) and O2(v 〉 0), and inclusion of vibrationally excited N2 and O2 brings the model and data into better agreement. The effects of vibrationally excited O2 and N2 on the electron density and temperature are most pronounced during daytime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-000-0957-2
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  • 5
    Electronic Resource
    Electronic Resource
    The role of vibrationally excited nitrogen in the ionosphere (1988)
    Springer
    Pure and applied geophysics 127 (1988), S. 529-544 
    Details
    ISSN: 1420-9136
    Keywords: Ionosphere ; nitrogen ; vibrational temperatures ; N2 and CO2 and populations of N2 and CO2 in the D, E and F regions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Theoretical and experimental aspects of the production, transformation, diffusion and loss of N2 in the upper atmosphere are considered. The N2-CO2 near-resonant system in theD andE regions is taken into account. We describe our understanding of the methods necessary to find the vibrational populations of N2 and CO2 (asymmetric mode of CO2). The calculations of the vibrational temperatures in theD, E, andF regions for the mid-latitude ionosphere and an aurora are presented. The connection between the excited species and the 4.26-μm radiation intensities is considered. The models for the rate coefficient of the reaction of O+ with N2 and the electron density decrease resulting from N2 in the F region are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879824
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanisms of the electron density depletion in the SAR arc region (1996)
    Springer
    Annales geophysicae 14 (1996), S. 211-221 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract This study compares the measurements of electron density and temperature and the integral airglow intensity at 630 nm in the SAR arc region and slightly south of this (obtained by the Isis 2 spacecraft during the 18 December 1971 magnetic storm), with the model results obtained using the time dependent one-dimensional mathematical model of the Earth’s ionosphere and plasmasphere. The explicit expression in the third Enskog approximation for the electron thermal conductivity coefficient in the multicomponent mixture of ionized gases and a simplified calculation method for this coefficient presents an opportunity to calculate more exactly the electron temperature and density and 630 nm emission within SAR arc region are used in the model. Collisions between N2 and hot thermal electrons in the SAR arc region produce vibrationally excited nitrogen molecules. It appears that the loss rate of O+(4S) due to reactions with the vibrationally excited nitrogen is enough to explain electron density depression by a factor of two at F-region heights and the topside ionosphere density variations within the SAR arc if the erosion of plasma within geomagnetic field tubes, during the main phase of the geomagnetic storm and subsequent filling of geomagnetic tubes during the recovery phase, are considered. To explain the disagreement by a factor 1.5 between the observed and modeled SAR arc electron densities an additional plasma drift velocity \sim-30 m s−1 in the ion continuity equations is needed during the recovery phase. This additional plasma drift velocity is likely caused by the transition from convecting to corotating flux tubes on the equatorward wall of the trough. The electron densities and temperatures and 630 nm integral intensity at the SAR arc and slightly south of this region as measured for the 18 December 1971 magnetic storm were correctly described by the model without perpendicular electric fields. Within this model framework the effect of the perpendicular electric field \sim100 mv m−1 with a duration \sim1 h on the SAR arc electron density profiles was found to be large. However, this effect is small if \sim1-2 h have passed after the electric field was set equal to zero.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-996-0211-7
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  • 7
    Electronic Resource
    Electronic Resource
    The role of vibrationally excited nitrogen in the formation of the mid-latitude negative ionospheric storms (1994)
    Springer
    Annales geophysicae 12 (1994), S. 554-564 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Millstone Hill ionospheric storm time measurements of the electron density and temperature during the ionospheric storms (15-16 June 1965; 29–30 September 1969 and 17–18 August 1970) are compared with model results. The model of the Earth’s ionosphere and plasmasphere includes interhemispheric coupling, the H+, O+(4S), O+(2D), O+(2P), NO+, O+2 and N+2 ions, electrons, photoelectrons, the electron and ion temperature, vibrationally excited N2 and the components of thermospheric wind. In order to model the electron temperature at the time of the 16 June 1965 negative storm, the heating rate of the electron gas by photoelectrons in the energy balance equation was multiplied by the factors 5–30 at he altitude above 700 km for the period 4.50-12.00 LT, 16 June 1965. The [O]/[N2] MSIS-86 decrease and vibrationally excited N2 effects are enough to account for the electron density depressions at Millstone Hill during the three storms. The factor of 2 (for 27–30 September 1969 magnetic storm) and the & actor 2.7 (for 16–18 August 1970 magnetic storm) reduction in the daytime peak density due to enhanced vibrationally excited N2 is brought about by the increase in the O++N2 rate factor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-994-0554-x
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  • 8
    Electronic Resource
    Electronic Resource
    Anomalous electron density events in the quiet summer ionosphere at solar minimum over Millstone Hill (1998)
    Springer
    Annales geophysicae 16 (1998), S. 460-469 
    Details
    ISSN: 0992-7689
    Keywords: Ionosphere (Ion chemistry and composition Ionosphere-atmosphere interactions Mid-latitude ionosphere)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract This study compares the observed behavior of the F region ionosphere over Millstone Hill with calculations from the IZMIRAN model for solar minimum for the geomagnetically quiet period 23–25 June 1986, when anomalously low values of hmF2(〈200 km) were observed. We found that these low values of hmF2 (seen as a G condition on ionograms) exist in the ionosphere due to a decrease of production rates of oxygen ions resulting from low values of atomic oxygen density. Results show that determination of a G condition using incoherent scatter radar data is sensitive both to the true concentration of O+ relative to the molecular ions, and to the ion composition model assumed in the data reduction process. The increase in the O+ + N2 loss rate due to vibrationally excited N2 produces a reduction in NmF2 of typically 5–10%, but as large as 15%, bringing the model and data into better agreement. The effect of vibrationally excited NO+ ions on electron densities is negligible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-998-0460-8
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  • 9
    Electronic Resource
    Electronic Resource
    Cooling rate of thermal electrons by electron impact excitation of fine structure levels of atomic oxygen (1999)
    Springer
    Annales geophysicae 17 (1999), S. 919-924 
    Details
    ISSN: 0992-7689
    Keywords: Atmospheric composition and structure (thermosphere - composition and density) ; Ionosphere (mid-latitude ionosphere; modelling and forecasting)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The atomic oxygen fine structure cooling rate of thermal electrons based on new effective collision strengths for electron impact excitation of the ground-state 3P fine-structure levels in atomic oxygen have been fitted to an analytical expression which is available to the researcher for quick reference and accurate computer modeling with a minimum of calculations. We found that at the F region altitudes of the ionosphere the new cooling rate is much less than the currently used fine structure cooling rates (up to a factor of 2–4), and this cooling rate is not the dominant electron cooling process in the F region of the ionosphere at middle latitudes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-999-0919-2
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  • 10
    Electronic Resource
    Electronic Resource
    Comparison of model electron densities and temperatures with Millstone Hill observations during undisturbed periods and the geomagnetic storms of 16–23 March and 6–12 April 1990 (1997)
    Springer
    Annales geophysicae 15 (1997), S. 327-344 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Measurements of F-region electron density and temperature at Millstone Hill are compared with results from the IZMIRAN time-dependent mathematical model of the Earth’s ionosphere and plasmasphere during the periods 16–23 March and 6–12 April 1990. Each of these two periods included geomagnetically quiet intervals followed by major storms. Satisfactory agreement between the model and the data is obtained during the quiet intervals, provided that the recombination rate of O+(4S) ions was decreased by a factor of 1.5 at all altitudes during the nighttime periods 17–18 March, 19–20 March, 6–8 April and 8–9 April in order to increase the NmF2 at night better to match observations. Good model/data agreement is also obtained during the storm periods when vibrationally excited N2 brings about factor-of-2-4 reductions in daytime NmF2. Model calculations are carried out using different expressions for the O+ – O collision frequency for momentum transfer, and the best agreement between the electron-density measurements and the model results is obtained when the CEDAR interim standard formula for the O+ – O collision frequency is used. Deviations from the Boltzmann distribution for the first five vibrational levels of NI were calculated. The calculated distribution is highly non-Boltzmann at vibrational levels j 〉 2, and the Boltzmann distribution assumption results in the increase of 10–30% in calculated NmF2 during the storm-time periods. During the March storm at solar maximum the model results obtained using the EUVAC solar flux model agree a little better with the observations in comparison with the EUV94 solar flux model. For the April storm period of moderate solar activity the EUV94X model results agree better with the observations in comparison to the EUVAC model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-997-0327-4
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