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Ann. Geophys., 23, 2369-2375, 2005
www.ann-geophys.net/23/2369/2005/
© European Geosciences Union 2005
Observations of neutral winds, wind shears, and wave structure during a sporadic-E/QP event
M. F. Larsen1, M. Yamamoto2, S. Fukao2, R. T. Tsunoda3, and A. Saito4
1Department of Physics, Clemson University, Clemson, SC, USA
2Research Institute of Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
3SRI International, Menlo Park, CA, USA
4Department of Geophysics, Kyoto University, Kyoto 606-8502, Japan
Abstract. The second Sporadic E Experiment over Kyushu (SEEK-2) was carried out
on 3 August 2002, during an active sporadic-E event that also showed
quasi-periodic (QP) echoes.
Two rockets were launched into the event from Kagoshima Space Center in
southern Japan 15 min apart.
Both carried a suite of instruments, but the second rocket also
released a trimethyl aluminum (TMA) trail to measure the neutral winds
and turbulence structure.
In a number of earlier measurements in similar conditions, large winds
and shears that were either unstable or close to instability were
observed in the altitude range where the ionization layer occurred.
The SEEK-2 wind measurements showed similar vertical structure, but unlike
earlier experiments, there was a significant difference between the
up-leg and down-leg wind profiles.
In addition, wave or billow-like fluctuations were evident in the
up-leg portion of the trail, while
the lower portion of the down-leg trail was found to have
extremely strong turbulence that led to a rapid break-up of the trail.
The large east-west gradient in the winds and the strong turbulence
have not been observed before.
The wind profiles and shears, as well as the qualitative characteristics
of the strong turbulence are presented, along with a discussion of
the implications of the dynamical features.
Keywords. Ionosphere (Mid-latitude ionosphere; Ionospheric
irregularities; Electric field and currents)
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