Geoscience Reference
In-Depth Information
of the stronger negative IMF
B
y
component and of the increase of the IMF amplitude
in general. The position of the modeled dusk circulation cell at 74
ı
geomagnetic
latitude near 18:30 MLT did not change very much, but the area occupied by both the
plasma convection and the neutral wind circulation increased during the transition
toward more intense IMF values. The approximate coincidence of the modeled and
observed phase of this neutral wind circulation cell as well as the agreement of
the corresponding amplitudes along the track lends credit to the correctness of the
simulations.
Future model runs and comparisons with more abundant, independent concurrent
measurements of both ground-based and in situ observations opens the way to
detailed analyses of the high-latitude upper atmosphere dynamics and to the
understanding of mesoscale structures of the highly dynamic and complex system.
With new upcoming missions such as the Swarm ionospheric multisatellite project,
or the EISCAT 3-D project, the time has come to take into account variations in
all three dimensions simultaneously, as they occur in the real ionosphere (Amm
et al.
2008
). Global numerical first-principle modelings such as the UAM presented
here or more specified numerical tools (e.g., Song et al.
2009
) allow a much
more comprehensive analysis of the physical processes involved, provided they are
suited with, among others, their temporal and spatial resolutions and their boundary
condition formulations, etc., to the subject of the investigation, which here is the
upper atmosphere dynamics at high latitudes in the global context of solar radiation
and solar wind-driven external forcings.
4.3.5
Seismogenic Electric Fields and Their Ionospheric
Effects
4.3.5.1
Introduction
Seismogenic electric fields generated near the tectonic faults are important elements
of the global electric circuit (e.g., Harrison et al.
2010
; Pulinets and Boyarchuk
2004
, and references therein; Freund
2011
; Pulinets and Ouzounov
2011
; Sorokin
and Chmyrev
1999
; Sorokin et al.
2007
). We consider next their ionospheric
effects mainly in the total electron content (TEC) variations as possible ionospheric
precursors of earthquakes.
The statistically distinguished TEC pre-earthquake signatures are often described
(Liu et al.
2006b
; Pulinets and Boyarchuk
2004
; Zakharenkova et al.
2007a
)as(1)
anomalous strong (30-90% and more deviations relative to the quiet conditions)
TEC-positive or -negative modifications (increases or reductions) before the forth-
coming seismic event not less than M5 by magnitude linked to the near-epicenter
area. According to I.E. Zakharenkova, positive ones are more often reported. The
typical zone of the anomaly maximum manifestation extends greater than 1,500 km
in latitude and 3,500-4,000 km in longitude. The shapes and dimensions of the
disturbed areas are kept rather stable. (2) Local long-living anomaly formation
