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Royal Observatory of Belgium - Meridian Room

Plasmaspheric study with VLF antennas installed in Antarctica and in Belgium and with an empirical plasmaspheric model


  • Dr. Fabien DARROUZET

Primary authors



In January-February 2016, we have installed a compact magnetic antenna augmented with data processing equipment at the Belgian Princess Elisabeth station (71°57’S - 23°20’E; 1380 m altitude; L$\sim$5.5R$_{E}$). This VLF antenna is composed of two search coils in a waterproof plastic box, inside a wooden thermal insulated box, fixed on the top of a wooden table. This antenna records VLF (Very Low Frequency, 3-30 kHz) whistler waves, from which we can infer information about the state of the plasmasphere, an inner region of the Earth’s magnetosphere. The Princess Elisabeth station is a very interesting place for such an instrument because of the low electromagnetic activity at and around the station, which usually perturb the measurements. Also, this location at very high magnetic latitude provides information on variations in the plasmaspheric boundary position. Such an antenna complements another antenna that we have installed seven years ago in Humain, Belgium (50°12’N - 5°15’E; 240 m altitude; L$\sim$2.3R$_{E}$). This VLF antenna is made of two perpendicular magnetic loops, oriented North-South and East-West, and with an area of approximately 50 m$^{2}$ each. Those two antennas are part of the international global network AWDA (Automatic Whistler Detector and Analyzer). The ultimate goal of this network is to provide data to feed a data-assimilative model of the plasmasphere. Data from both stations can be compared with an empirical plasmaspheric model, developed here at BIRA-IASB. This 3D dynamical model is based on the interchange instability mechanism using the convection electric field model E5D. It is a function of the level of geomagnetic activity level index Kp observed during the date given as input and 24 hours before. This model provides the plasmapause location in terms of radial distance and magnetic local time, as well as the electron density and temperature of the plasmasphere.