[7] The experimental data obtained at the chain of the ground-based ionospheric stations (GIS) are analyzed below. The stations were located along the part of the Mir orbit where AS were registered. The hypothesis (first proposed by Kalinin and Sergeenko [2002]) is considered that prior to strong earthquakes, macroscale irregularities (of the very kind which according to Danilkin [1994] is able to explain a formation of AS) may be formed in the vicinity of the earthquake epicenters. Such interpretation of the data of Kalinin and Sergeenko [2002] and Kalinin et al. [2001] requires a detailed comparison of the features of the orbit motion of Mir to the motions of the irregularities at the F2 -maximum height caused by this or that earthquakes in the days of AS registration.
|
|
| Figure 2 |
[8] Figure 2 shows the d foF2(t) dependencies for three GIS (designated by the first letters of the places of their location). The observations indicate to the presence of travelling singular macroirregularities. The lower abscissa (letter E) refers to the epicenter region, the three lower abscissas refer to three stations. The vertical shift is proportional to the distance from the GIS to the epicenter. Time is counted for all four abscissas from the moment 0000 UT on 29 April 1999 (vertical line). From each of the upper three abscissas the value of the relative variation d foF2(t) of the critical frequency measured by the corresponding GIS is counted. The scale is shown as a stretch in the middle of the right-hand side of Figure 2.
[9] The earthquake moment is shown by a cross.
Solid circles
correspond to three positive "pulses" closest to the earthquake. For
Darwin they are prior the earthquake and for Ahmedabad and Roma
they are
after the earthquake. The middles of the pulse bases projected to
the abscissa are shown by solid circles. According to the theory of
Kalinin and Sergeenko [2002],
the dashed line shows the motion
with a velocity of
V 
900 m s
-1 of an object having been formed 12 hours
prior to the earthquake and shifted during 21 hours
to a distance of 18,000 km.
It should be noted that according to
Kalinin et al. [2001]
the
relative variability of the irregularity shape in the vicinity of its center
is well modeled by the
1/cosh x function,
x being the shift from the
center.
Citation: (2004), Discussion paper: Macroscale ionospheric irregularities registered by the Mir onboard ionosonde, Int. J. Geomagn. Aeron., 5, GI1002, doi:10.1029/2003GI000038.
Copyright 2004 by the American Geophysical Union