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Ann. Geophys., 23, 2377-2384, 2005
www.ann-geophys.net/23/2377/2005/
© European Geosciences Union 2005
Numerical simulation of mid-latitude ionospheric E-region based on SEEK and SEEK-2 observations
T. Yokoyama1,3, M. Yamamoto1, S. Fukao1, T. Takahashi2, and M. Tanaka2
1Research Institute for Sustainable Humanosphere, Kyoto University, Kyoto, Japan
2Information Science Laboratory, Tokai University, Kanagawa, Japan
3now at: Solar-Terrestrial Environment Laboratory, Nagoya University, Aichi, Japan
Abstract. Observational campaigns of the mid-latitude ionospheric E-region
with sounding rockets and ground-based instruments were conducted
in 1996 (SEEK) and 2002 (SEEK-2).
Both of them were successfully conducted to bring
important findings about the mid-latitude E-region
and quasi-periodic (QP) VHF radar echoes.
The observational results in the SEEK and the SEEK-2 are compared
with numerical simulations and discussed in this paper.
While sporadic-E (Es)-layers are actually
formed by the observed neutral wind,
it is difficult for the constant wind shear to produce
the sharp Es-layer gradient.
However, once they are formed in the lower E-region,
they cannot easily be dissipated by the simple diffusive motion.
The polarization electric field, calculated under the condition at
the rocket launch time, shows similar amplitude and structure
to the measurement around the Es-layer altitude.
The structure of the plasma density and the electric field above
the Es-layer observed in the SEEK-2 showed
a wave-like pattern up to an altitude of 150 km.
Considering a mapping of the polarization electric field
generated within the Es-layers,
gravity waves are the possible source of the wave-like structure of
the measured electric fields and sub-peaks of the electron density
above the main Es-layers.
Fluctuation of the measured magnetic field is
reproduced by Hall or field-aligned current
driven by the polarization electric field.
The current theoretical models for QP echoes and the polarization electric
field are basically verified by the discussion in this paper.
Keywords. Ionospheric irregularities – Mid-latitude ionosphere
– Numerical simulation studies
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