PROBLEMS OF GEOCOSMOS

Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008)
SEISMIC TRAVELLING IONOSPHERE DISTURBANCES AT F2-REGION IN
TIME OF HELIOGEOPHYSICAL DISTURBANCES
N.P. Sergeenko, M.V. Rogova, A.V. Sazanov
Pushkov Institute of Terrestrial magnetism, Ionosphere and Radio waves propagation,
Troitsk, Moscow region, 142190, Russia, e-mail: serg@izmiran.ru
Abstact. The properties of travelling ionospheric disturbances (TID) (their horizontal sizes are 1~
4 thousand kms, excesses from the background are 15-30 %), formed in F2 layer as a result of
preparation of the strong earthquake in time of heliogeophysical perturbations are explored. The
inhomogeneities arise 10-15 h before earthquakes and move horizontally with a transonic speed on
distances of a few thousand kms up to round – the - world trajectories focused approximately
along an arc of a major circle, transmitted above an epicenter region. Select of macro-scale
irregularities was caused by spatial - time differences of dynamics of F2-layer of the ionosphere in
time of the heliogeophysical disturbances from dynamics of quasi-causative seismic macroscale
ionospheric inhomogeneities.
The complex analysis of the arrays of critical frequencies of F2 - layer of the ionosphere (foF2) of
a world network of automatic ground ionospheric stations of vertical sondage was carried out. As a
result of these examinations, the geophysical patterns of ionospheric effects incipient at
superimposition of macroscale inhomogeneities and ionospheric disturbances of solar and
magnitospheric origin were synthesized.
INTRODUCTION
This work is devoted to the study of the possibilities of detection of traveling disturbances (TIDs) of
seismic origin in the main peak of ionosphere at the time of heliogeophysical disturbances. The sizes of
irregularities reach 1~3 thousand kms, lifetimes exceed 10 4 sec, and moving distances are 10~15 thousand kms,
the speeds are approximate to sonic velocity. It was also established that the formation of TID precedes 10~15
hrs to the moment of catastrophic earthquakes with magnitude М ≥ 6 and localization ~1 thousand kms from the
epicenter of the earthquake (Kalinin and Sergeenko, 2002; Kalinin et al, 2003; Sergeenko and Kharitonov,
2005). Perturbations of electron concentration, commensurable in sizes and contrast range with seismic TIDs,
but completely different character of temporal and spatial changes, can appear on the conditions of ionospheric
storms and substorms. Below we review features of occurrence of TID in quiet and disturbed heliogeophysical
conditions.
DATA ANALYSIS
Files of values of relative variation of critical frequencies of F2 layer of the ionosphere by the global
network of ionospheric stations of vertical sounding δfoF2 were used in the analysis as a main source of
information about seismic TID: δfoF2 = (foF2- foF2m)/foF2m , foF2m – moving median [Gaivoronskaya et al.,
1971). {δfoF2} are used for detection and numerical characterization of ionosphere disturbances (Zevakina et
al., 1990). It does not depend on multiplicative errors of representation foF2 due to the use of various scales at
stations of vertical sounding, gives "protection" against inadequate influence of major "emissions" and excludes
regular seasonal and daily variability.
The seismic TIDs are selected as a local irregularity with extreme value (δfoF2)max ≥15 % at the middle
latitudes and (δfoF2)max ≥10 % at low latitudes. It is also supposed that during of 2~3 hours diversion should be
more than 10 %. Kp, Dst, and AE indices were used for the description of geomagnetic situation.
The quite conditions.
In fig. 1a we can see an example of variations δfoF2(t) for different ionospheric stations for the earthquake,
which occurred at Alyaska on 09.03.1985 (ϕ=66,6N; λ=150,5W; t0=14 h 08 m UT; M=6,2), a vertical line marks
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