Demeter Observations of ELF/VLF Signals Generated through Modulated Heating of the Auroral Electrojet by the HAARP HF Transmitter

MANUEL PLATINO; UMRAN INAN; TIMOTHY BELL

Santa Fe, New Mexico, Estados Unidos

Workshop; Joint CEDAR-GEM Workshop; 2005

Rice University

Amplitude modulated HF transmissions into the ionosphere have been used to generate ELF/VLF signals which propagate into the plasmasphere and the magnetosphere. The process of generation of these ELF/VLF waves involves the modulation of auroral electrojet currents through changes in the ionospheric conductivity induced by the HF ionospheric heater. Many observations of similarly generated ELF/VLF signals have been made on the ground, and afew observations have also been carried out in space during medium / high-altitude satellite passes. The present work presents a study of the ELF/VLF radiated power from the auroral electrojet induced by the HF heater of the High-Frequency Active Auroral Research Program (HAARP) facility in Gakona, Alaska. Our study concerns measurements on ground receivers near the facility, as well as ground-satellite conjunction observations conducted using the DEMETER low altitude satellite. Located near the magnetic shell at L=5, HAARP has extensively been used for ionosphere-to-ground type of ELF/VLF wave-injection experiments, and several studies of the radiated power measured on the ground have recently been performed. The DEMETER spacecraft presents a unique opportunity to significantly enhance this study, being able to measure the three spatial components of both the electric and magnetic fields in the ELF range and one componen of each field in the VLF range. In the present paper, we present recent results of these measurements and give an estimate of the ELF/VLF power radiated into the magnetosphere, as well as to the ground, by the auroral electrojet currents modulated by the HAARP HF heater.