Geoscience Reference
In-Depth Information
∆λ ≤ 13°. Over sources of moderate earthquakes (EQ
29
and its aftershocks EQ
30,34,39
)
and light earthquake EQ
37
, the electric field is perpendicular to the magnetic field line
(or to the magnetic field) for orbits 250, 251, and 258. Ions and electrons are moving
perpendicular to the plane determined by the electric and magnetic vectors. They can-
not immediately compensate the charge that causes the electric field, so this field is
expanded into a large area.
Concerning Low Latitudes
Numerous ionospheric anomalies in the quasi-static electric field at low latitudes in-
dicate an increase in the vertical components
E
z
of about 10-8 mV/m (in the cases
of ∆λ ≤ 1-14°) to 10-2 mV/m (for ∆λ ≤ 6-16°) around 13-25 hr to 7-19 hr respec-
tively before and after moderate earthquakes which are related to seismic events in
the Southern Hemisphere. There are not observations about analogous disturbances
100 hr before and 9 hr after moderate earthquakes in cases of seismic activity in the
Northern Hemisphere.
Concerning High and Middle Latitudes
The observed anomalies in ionospheric zones, that have supposed relations with earth-
quakes in regions at high and middle latitudes of the Southern and Northern
Hemisphere, are summarized as an increase in the vertical component
E
z
of about 10
mV/m (in the cases of ∆λ ≤ 1-18°) to 2 mV/m (for ∆λ ≤ 5-18°) around 80-96 hr before
and after moderate seismic manifestations.
The recent results for high latitudes and the results from our previous chapter for
Southern Ocean and Greenland Sea (Gousheva et al., 2008b) confi rm the empirical
models of Heppner (1977), Heppner and Maynard (1987), and the electric convection
fi eld model proposed by Heelis et al. (1982).
The obtained results strengthen our previous studies and conclusions for middle
latitudes (Gousheva et al., 2008a). Often the intense disturbances in electric fi eld com-
ponents are especially observed at high latitudes under complicated conditions and
these disturbances are marked usually in the open fi eld lines that provoke rare penetra-
tion in geomagnetic mid-latitudes.
Strong and Major Earthquakes
Concerning Low Latitudes of the Southern Hemisphere
The observed anomalies in ionospheric zones, that have supposed relations with earth-
quakes in regions at low latitudes of the Southern Hemisphere, are summarized as an
increase in the vertical component
Ez
of about 18 mV/m (for ∆λ ≤ 1°) to 12 mV/m (for
∆λ ≤ 20°) around 306-300 hr before and after major seismic manifestations.
Concerning Middle Latitudes of the Northern Hemisphere
The observed anomalies in ionospheric zones, that could be related to earthquakes in
regions at middle latitudes of the Northern Hemisphere, are summarized as an increase
in the vertical component
E
z
of about 15 mV/m (for ∆λ ≤ 18°) to 10 mV/m (for ∆λ ≤
9°) around 153-91 hr before and after strong seismic manifestations.
