PRELIMINARY RESULTS OF LOWER IONOSPHERE MONITORING BASED ON ANALYSIS OF TWEEK-ATMOSPHERICS

Abstract

The altitude interval and the low concentration of charged particles in the lower ionosphere reduce the possibilities of its investigation by using radio sounding, balloons, rockets, or satellites. We use the tweek-atmospherics (tweeks) in this work for studying the lower ionosphere. Tweeks are the ELF–VLF radio pulses excited by lightning strokes in the Earth-ionosphere waveguide. A new method is suggested and used of automated identification and analysis of tweeks. On the basis of the tweek analysis recorded in August 2014, the relationship was investigated between the regular variations in the ionosphere height caused by changes in the solar zenith angle, which determines the main source of ionization in ambient night conditions - the radiation from geocorona. We demonstrate that elevation of the lower boundary of the ionosphere increases the flux rate of tweeks, and the effect is associated with the decrease of losses in the ionosphere. The elevation of ionosphere lower boundary was detected during the moderate geomagnetic storm. Thus, the diagnostic capabilities of the proposed method were demonstrated, which allow for locating the thunderstorm centers and to reveal the height variations of the Earth-ionosphere waveguide along the propagation paths of VLF radio waves excited by lightning discharges from different thunderstorms.