Monitoring the Ground-Based VLF transmissions from Space using IMAGE RPI

Using the global network of ground-based VLF transmitters operating at frequency between 10 and 30 kHz, we have monitored the occurrence of whistler mode VLF signals with the RPI instrument on the IMAGE satellite. Our objective was to study the power and effective spatial scales of the whistler waves propagating trough the ionosphere into the magnetosphere. We have identified signals from 20 stations in the plasmasphere region with L shells ranging from 1.1 to 5.2. Ten of these stations have high radiated power, 200 kW to 1 MW. The spatial region where VLF signals were observed was significantly smaller during the dayside measurements than during the nightside ones. We also present azimuthal and radial characteristics of the VLF signal amplitude.