Implementation of a low-energy VLF data logger for characterizing the lower ionosphere at Ibadan

Abstract

This study implemented a very low frequency (VLF) data logger for monitoring the local 
ionosphere. The VLF data logger was built around a Raspberry Pi 3B+. A 1 m2 loop antenna 
with a sensitivity of 5.86 × 10-4 V/s1/2m-1 was built to receive the VLF signal. The system 
recorded three frequencies: 19.2, 19.58, and 19.8 kHz from South Vijayanarayanam 
(India), Anthorn (UK), and Exmouth (Australia), respectively, at Ibadan, Nigeria. Three 
months (June–August 2019) of data were reported in this study. The results revealed that 
the data logger saves up to 83% energy compared to an average laptop. The system was 
able to characterize the diurnal morphology of the D-layer. The diurnal morphology shows 
the sunrise and the sunset effect (signature). It was noted that variations exist in the aver
age signal strength on quiet days; therefore, further study is recommended to investigate 
the geophysical conditions that are responsible for these variations.