Electromagnetic Effects Resulted from Natural Disasters - Ultra and Extremely Low Frequency Electromagnetic Fields - page 404

weak signals were identified because the exceptionally deep solar minimum on this
day provided ideal conditions to identify these signals in the background noise.
However, it appears that the practical application of electromagnetic monitoring
for tsunami wave propagation is extremely limited except for periods of low solar
activity.
Alternative methods in tsunami wave monitoring have been the subject of special
interest during recent years. It was hypothesized that tsunami waves in the open
ocean can generate IGWs which in turn may result in the ionospheric perturbations
(Hines 1972 ; Peltier and Hines 1976 ; Pavlov and Sukhorukov 1987 ). In the period
range of 10-20 min the horizontal velocity of IGW is close to that of tsunami
wave whereas the vertical IGW velocity is about 50 m/s, so that the IGW-induced
perturbations in the ionosphere have a time lag about several hours. The short-scale
ionospheric TEC perturbations with the same characteristic have been observed in
Japan after the M w D 8:2 EQ in Peru on June 23, 2001 (Artru et al. 2005 ). The
measurements were made around the time of tsunami wave arrival. The ionospheric
perturbations observed during the giant tsunami following the Sumatra-Andaman
event on December 26, 2004 (M w D 9:3), the 2009 Samoa and 2010 Chile tsunamis
have been reported by DasGupta et al. ( 2006 ), Liu et al. ( 2006 ), Lognonné et al.
( 2006 ), Occhipinti et al. ( 2006 , 2013 ), Rolland et al. ( 2010 ), and Galvan et al.
( 2011 ). As these perturbations are really associated with tsunami wave propagation,
the atmospheric and ionospheric remote sensing can provide a new tool for oceanic
monitoring and tsunami detection.

10.2.3 Space-Borne Measurements over Hurricanes

and Typhoons

The effect of intense meteorological processes in the bottom atmosphere on the
ionospheric parameters have been examined by Kelley et al. ( 1985b ), Holzworth
et al. ( 1985 ), and Korepanov et al. ( 2009 ). Space-borne measurements over an
active typhoon have shown variations of the plasma conductivity and the ionospheric
electric field at the frequencies below 100 kHz. Mikhailova et al. ( 2000 , 2002 )
have reported the satellite observations of the ULF/ELF ionospheric perturbations
over powerful typhoons in the Pacific Ocean. The electric field perturbations in the
ionosphere over a tropical storm region have been measured onboard the COSMOS-
1809 satellite (Isaev et al. 2002 ; Sorokin et al. 2005 ). The amplitude of electric
perturbations reached an abnormally high value about 25 mV/m, which is not typical
for the equatorial ionosphere. This effect is supposed to be due to the vertical
electric current associated with the amplification of vertical air convective motion
or turbulent transfer in the lower atmosphere.
Some of electromagnetic phenomena observed over hurricanes and typhoons are
believed to be due to the CG and IC lightning or due to high altitude discharges
such as Red sprites and Blue jets (BJs), which are developed over a thunderstorm.