New Parameter for Analysis of Ionospheric Disturbances and the Search for Ionospheric Precursors of Earthquakes Based on Barbier's Formula

A new relative parameter (delta(Barbier)) is proposed for the analysis of ionospheric disturbances and the search for ionospheric precursors of earthquakes. The parameter is derived on the basis of the semiempirical Barbier's formula, in which directly and simultaneously measured ionospheric parameters are used: the critical frequency of F2 layer of the ionosphere foF2 and the virtual minimum height of F region h'F. The time prior to a 6.2-magnitude earthquake that occurred in the vicinity of the ground-based station of vertical ionospheric sounding MAUI (Hawaii) on June 26, 1989, is considered as an example of the use of this parameter and its interpretation. We show that delta(Barbier) <= 0 during dark hours, from 2000 to 0400 local time, against the geomagnetically quiet background (Kp <= 2(+)) on June 25, 1989, i.e., the day before the earthquake. This behavior is interpreted as a decrease (as compared to the median) in the glow intensity of the atomic oxygen O(D-1) emission in the red line (630 nm) estimated from ionospheric data, which is associated with the dissociative recombination of ions at altitude of the F region during this time. The studied effect can be seismogenic and can serve an ionospheric precursor of an earthquake.