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| Titel |
Comparison of the measured and modelled electron densities and temperatures in the ionosphere and plasmasphere during 20-30 January, 1993 |
| VerfasserIn |
A. V. Pavlov, T. Abe, K.-I. Oyama |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 18, no. 10 ; Nr. 18, no. 10, S.1257-1262 |
| Datensatznummer |
250014076
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| Publikation (Nr.) |
 copernicus.org/angeo-18-1257-2000.pdf |
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| Zusammenfassung |
We present a comparison of the electron
density and temperature behaviour in the ionosphere and plasmasphere measured by
the Millstone Hill incoherent-scatter radar and the instruments on board of the
EXOS-D satellite with numerical model calculations from a time-dependent
mathematical model of the Earth's ionosphere and plasmasphere during the
geomagnetically quiet and storm period on 20–30 January, 1993. We have evaluated
the value of the additional heating rate that should be added to the normal
photoelectron heating in the electron energy equation in the daytime
plasmasphere region above 5000 km along the magnetic field line to explain the
high electron temperature measured by the instruments on board of the EXOS-D
satellite within the Millstone Hill magnetic field flux tube in the Northern
Hemisphere. The additional heating brings the measured and modelled electron
temperatures into agreement in the plasmasphere and into very large disagreement
in the ionosphere if the classical electron heat flux along magnetic field line
is used in the model. A new approach, based on a new effective electron thermal
conductivity coefficient along the magnetic field line, is presented to model
the electron temperature in the ionosphere and plasmasphere. This new approach
leads to a heat flux which is less than that given by the classical Spitzer-Harm
theory. The evaluated additional heating of electrons in the plasmasphere and
the decrease of the thermal conductivity in the topside ionosphere and the
greater part of the plasmasphere found for the first time here allow the model
to accurately reproduce the electron temperatures observed by the instruments on
board the EXOS-D satellite in the plasmasphere and the Millstone Hill
incoherent-scatter radar in the ionosphere. The effects of the daytime
additional plasmaspheric heating of electrons on the electron temperature and
density are small at the F-region altitudes if the modified electron heat flux
is used. 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 the first vibrational levels of N2 and O2 and the
second level of O2, and the calculated distributions of N2(v)
and O2(v) are highly non-Boltzmann at vibrational levels v
> 2. The resulting effect of N2(v > 0) and O2(v
> 0) on NmF2 is the decrease of the calculated daytime NmF2 up to a factor of
1.5. The modelled electron temperature is very sensitive to the electron
density, and this decrease in electron density results in the increase of the
calculated daytime electron temperature up to about 580 K at the F2 peak
altitude giving closer agreement between the measured and modelled electron
temperatures. Both the daytime and night-time 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.
Key words: Ionosphere (ionospheric disturbances;
ionosphere-magnetosphere interactions; plasma temperature and density)
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