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Ann. Geophys., 24, 2553-2572, 2006
www.ann-geophys.net/24/2553/2006/
© European Geosciences Union 2006
The role of the zonal E×B plasma drift in the low-latitude ionosphere at high solar activity near equinox from a new three-dimensional theoretical model
A. V. Pavlov
Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio-Wave Propagation, Russian Academy of Science (IZMIRAN), Troitsk, Moscow Region, 142190, Russia
Abstract. A new three-dimensional, time-dependent theoretical model
of the Earth's low and middle latitude ionosphere and plasmasphere has been
developed, to take into account the effects of the zonal
E×B plasma drift on the electron and ion number densities
and temperatures, where E and
B are the electric and geomagnetic fields,
respectively. The model calculates the number densities of O+(4S),
H+, NO+, O2+, N2+, O+(2D),
O+(2P), O+(4P), and O+(2P*) ions, the electron
density, the electron and ion temperatures using a combination of the
Eulerian and Lagrangian approaches and an eccentric tilted dipole
approximation for the geomagnetic field. The F2-layer peak density, NmF2, and
peak altitude, hmF2, which were observed by 16 ionospheric sounders during
the 12–13 April 1958 geomagnetically quiet time high solar activity period
are compared with those from the model simulation. The reasonable agreement
between the measured and modeled NmF2 and hmF2 requires the modified equatorial
meridional E×B plasma drift given by the
Scherliess and Fejer (1999) model and the modified NRLMSISE-00 atomic oxygen
density. In agreement with the generally accepted assumption, the changes in
NmF2 due to the zonal E×B plasma drift are
found to be inessential by day, and the influence of the zonal
E×B plasma drift on NmF2 and hmF2 is found to
be negligible above about 25° and below about –26° geomagnetic
latitude, by day and by night. Contrary to common belief, it is shown, for the
first time, that the model, which does not take into account the zonal
E×B plasma drift, underestimates
night-time NmF2 up to the maximum factor of 2.3 at low geomagnetic latitudes,
and this plasma transport in geomagnetic longitude is found to be important
in the calculations of NmF2 and hmF2 by night from about –20° to about
20°
geomagnetic latitude. The longitude dependence of the night-time low-latitude
influence of the zonal E×B
plasma drift on NmF2, which is found for the first time, is explained in
terms of the longitudinal asymmetry in B (the eccentric
magnetic dipole is displaced from the Earth's center and the Earth's
eccentric tilted magnetic dipole moment is inclined with respect to the
Earth's rotational axis) and the variations of the wind induced plasma drift
and the meridional E×B plasma drift in geomagnetic
longitude. The study of the influence of the zonal
E×B plasma drift on the topside low-latitude
electron density is presented for the first time.
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