Доклади на Българската академия на науките Comptes rendus de l’Acad´ emie bulgare des Sciences Tome 59, No 8, 2006 EXPLORATIONS COSMIQUES SATELLITE OBSERVATIONS OF IONOSPHERIC DISTURBANCES ASSOCIATED WITH SEISMIC ACTIVITY M. Gousheva, R. Glavcheva * , D. Danov ** , I. Boshnakov ** (Submitted by Corresponding Member P. Velinov on June 21, 2006 ) Abstract To prove direct relationship between quasi-static electric field disturbances and seismic activity is a difficult task of the modern ionospheric physics. The paper presents new results from the detection of quasi-static electric field on board of INTERCOSMOS-BULGARIA-1300 satellite in the upper ionosphere above sources of moderate earthquakes. The quasi-static electric field plays an important role in the ionospheric physical processes. Some observational results in the case of small values of Kp index have been used in the search for correlation between the quasi-static elec- tric field anomalies and the seismic activity. An increase in the vertical component of the quasi-static electric field above earthquake sources is observed. These ionospheric effects could be connected to the appearance of sources of the quasi-static electric fields of seismic origin over observational events. Key words: satellite observation, quasi-static electric field, earthquake Introduction. The problem of earthquake prediction has stimulated the search for correlation between the seismic activity and ionospheric anomalies. For the first time an anomalous increasing of about 3-7 mV/m in the vertical component of the quasi-static electric field over a source of forthcoming earthquake in the near equatorial ionosphere is described by Chmyrev et al. [ 1 ]. We found an observational evidence of possible earthquake effects in the near-equatorial and low latitudinal ionosphere. An increase in the horizontal components and in the vertical component of the quasi-static electric 3 821