Whistler waves
When lightning strikes in one hemisphere, the lightning produces waves that propagate in space along the Earth's magnetic field lines from one hemisphere to the other one. They can then be detected in the other hemisphere. They are called whistlers, their frequency range is 5-15 kHz, their duration is about 1 second.
The whistlers tell us something about the density of electrons in the plasmasphere (the inner part of the magnetosphere) and boundaries that are visible within it.
AWDA project
We detect whistlers with ground-based VLF measurements as a part of the network AWDA (Automatic Whistler Detector and Analyzer).
This network covers low, mid and high magnetic latitudes including conjugate locations. It has been initiated by Dr. Janos Lichtenberger (Hungary). Worldwide, in 2022, 27 antennas were in operation and 15 were planned/in construction.
Our main goals:
- to build a statistical analysis of whistlers observed in Belgium,
- to derive density information along the magnetic field lines and in particular in the plasmasphere,
- to compare with density in-situ observations made by the Cluster satellites.
VLF antenna in Humain
We have installed a VLF antenna in October 2010 in Humain, Belgium (Lat.~50.11° N, Long.~5.15° E). The hardware has been installed during winter 2010-2011.
This VLF antenna is made of two perpendicular magnetic loops, oriented North-South and East-West and with an area of approximately 50 square meters each.
VLF antenna at Belgian Antarctic station Princess Elisabeth
We have installed a second VLF antenna in January 2016 at the Belgian Antarctic station Princess Elisabeth (Lat.~71.57° S, Long.~23.20° E), with the help of Dr. Janos Lichtenberger.
This VLF antenna is composed of two search coils, without a mast in order to withstand the weather at such latitudes. The antenna records whistlers automatically and the data are downloaded the following year.
