New Method for Determining the Lower Ionosphere Plasma Density by Tweek-Atmospherics: the Study of Applicability Limits

Tweek-atmospherics (tweeks), along with radio transmission by VLF radio stations, are used to study the lower ionosphere. The limits for using the new single-position method for determining of electron density in the lower ionosphere by results of analysis of multimodal tweek-atmospherics is studied upon the experimental records. The database accumulated at the Ukrainian Antarctic Station “Akademik Vernadsky” in 2019 has been used by clustering sources of tweeks. It is shown that the propagation West - East non-reciprocity results in the least attenuation for tweeks arriving from the geomagnetic east. In non-equatorial regions the method discussed can be used up to 10 Mm from receiving point for eastern tweeks and no more than 5 Mm for tweeks from western sector, and for tweeks with other propagation directions these limits lay at roughly 7 Mm from receiving station.